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This enzyme belongs to the family of [[lyase]]s, specifically the aldehyde-lyases, which cleave carbon-carbon bonds. The [[List of enzymes|systematic name]] of this enzyme class is '''mandelonitrile benzaldehyde-lyase (hydrogen cyanide-forming)'''. Other names in common use include '''hydroxynitrile lyase''', '''(R)-oxynitrilase''', '''oxynitrilase''', '''D-oxynitrilase''', '''D-alpha-hydroxynitrile lyase''', and '''mandelonitrile benzaldehyde-lyase'''. This enzyme participates in [[cyanoamino acid metabolism]]. It has 2 [[cofactor (biochemistry)|cofactors]]: [[Flavin group|flavin]], and [[flavoprotein]].
This enzyme belongs to the family of [[lyase]]s, specifically the aldehyde-lyases, which cleave carbon-carbon bonds. The [[List of enzymes|systematic name]] of this enzyme class is '''mandelonitrile benzaldehyde-lyase (hydrogen cyanide-forming)'''. Other names in common use include '''hydroxynitrile lyase''', '''(R)-oxynitrilase''', '''oxynitrilase''', '''D-oxynitrilase''', '''D-alpha-hydroxynitrile lyase''', and '''mandelonitrile benzaldehyde-lyase'''. This enzyme participates in [[cyanoamino acid metabolism]]. It has 2 [[cofactor (biochemistry)|cofactors]]: [[Flavin group|flavin]], and [[flavoprotein]].


== Historical Perspective ==
== Historical perspective ==
Mandelonitrile lyases, more colloquially referred to as HNLs (hydroxynitrile lyases) were first characterized by Wöhler in 1938, based off of their high activity in almond.<ref name=":0">{{Cite journal|last=Sharma|first=Monica|last2=Sharma|first2=Nitya Nand|last3=Bhalla|first3=Tek Chand|date=August 2005|title=Hydroxynitrile lyases: At the interface of biology and chemistry|url=https://linkinghub.elsevier.com/retrieve/pii/S0141022905001894|journal=Enzyme and Microbial Technology|volume=37|issue=3|pages=279–294|doi=10.1016/j.enzmictec.2005.04.013}}</ref> Since then, HNLs have been isolated from a wide variety of plants including stone fruits,<ref>Yemm RS, Poulton JE (1986). "Isolation and characterization of multiple forms of mandelonitrile lyase from mature black cherry (Prunus serotina Ehrh.) seeds". Arch. Biochem. Biophys. 247 (2): 440–5. doi:10.1016/0003-9861(86)90604-1. <nowiki>PMID 3717954</nowiki>.</ref> sorghum grains,<ref>Bovti, C., AND CONN, E. E. (1961) J. Bid Cfiem 236,207-210.</ref> millipedes,<ref>Dadashipour, M., Ishida, Y., Yamamoto, K., & Asano, Y. (2015). Discovery and molecular and biocatalytic properties of hydroxynitrile lyase from an invasive millipede,Chamberlinius hualienensis. ''Proceedings of the National Academy of Sciences,'' ''112''(34), 10605-10610. doi:10.1073/pnas.1508311112Motojima,</ref> and passion fruits.<ref name=":1">F. , Nuylert, A. and Asano, Y. (2018), The crystal structure and catalytic mechanism of hydroxynitrile lyase from passion fruit, Passiflora edulis. FEBS J, 285: 313-324. doi:10.1111/febs.14339</ref>
Mandelonitrile lyases, more colloquially referred to as HNLs (hydroxynitrile lyases) were first characterized by Wöhler in 1938, based on their high activity in almond.<ref name=":0">{{Cite journal|last=Sharma|first=Monica|last2=Sharma|first2=Nitya Nand|last3=Bhalla|first3=Tek Chand|date=August 2005|title=Hydroxynitrile lyases: At the interface of biology and chemistry|url=https://linkinghub.elsevier.com/retrieve/pii/S0141022905001894|journal=Enzyme and Microbial Technology|volume=37|issue=3|pages=279–294|doi=10.1016/j.enzmictec.2005.04.013}}</ref> Since then, HNLs have been isolated from a wide variety of plants including stone fruits,<ref>Yemm RS, Poulton JE (1986). "Isolation and characterization of multiple forms of mandelonitrile lyase from mature black cherry (Prunus serotina Ehrh.) seeds". Arch. Biochem. Biophys. 247 (2): 440–5. doi:10.1016/0003-9861(86)90604-1. <nowiki>PMID 3717954</nowiki>.</ref> sorghum grains,<ref>Bovti, C., AND CONN, E. E. (1961) J. Bid Cfiem 236,207-210.</ref> millipedes,<ref>Dadashipour, M., Ishida, Y., Yamamoto, K., & Asano, Y. (2015). Discovery and molecular and biocatalytic properties of hydroxynitrile lyase from an invasive millipede,Chamberlinius hualienensis. ''Proceedings of the National Academy of Sciences,'' ''112''(34), 10605-10610. doi:10.1073/pnas.1508311112Motojima,</ref> and passion fruits.<ref name=":1">F. , Nuylert, A. and Asano, Y. (2018), The crystal structure and catalytic mechanism of hydroxynitrile lyase from passion fruit, Passiflora edulis. FEBS J, 285: 313-324. doi:10.1111/febs.14339</ref>


HNLs are peculiar in that, within the same organism and even the same sample, there exist a variety of different [[Protein isoform|isoforms]] of this enzyme. These isoforms are not able to be determined from one another based off of factors influencing activity.<ref name=":2">Hu Z, Poulton JE. Molecular analysis of (R)-(+)-mandelonitrile lyase microheterogeneity in black cherry. ''Plant Physiol''. 1999;119(4):1535-46.</ref> This variety also results from macro-heterogeneity, as some isoforms bind [[Flavin adenine dinucleotide|FAD]] at their N-terminus while others are unable to bind FAD. It is understood that this is the case because the N-terminal fold is a region known to bind FAD as a needed [[Cofactor (biochemistry)|cofactor]]. Also curious is that FAD plays no observed role in active site [[Redox|oxidation-reduction reactions]] of this enzyme.<ref name=":0" /> Those HNLs that bind FAD do so at a [[Hydrophobic effect|hydrophobic]] region neighboring the active site where it is believed that the binding of FAD confers structural stability that allows for enzymatic action. These HNL, referred to as HNL Class I (or HNL I) are also noted to have N-terminus [[glycosylation]] and the distinct heterogeneity and presence of isoforms within the same organism. HNL Class II (HNL II), on the other hand, afford a wider variety of substrates, and in general favor (S) [[stereochemistry]], whereas HNL I [[Enantioselective synthesis|stereo-selectively]] produce (R)-mandelonitrile.<ref name=":0" />
HNLs are peculiar in that, within the same organism and even the same sample, there exist a variety of different [[Protein isoform|isoforms]] of this enzyme. These isoforms are not able to be determined from one another based on factors influencing activity.<ref name=":2">Hu Z, Poulton JE. Molecular analysis of (R)-(+)-mandelonitrile lyase microheterogeneity in black cherry. ''Plant Physiol''. 1999;119(4):1535-46.</ref> This variety also results from macro-heterogeneity, as some isoforms bind [[Flavin adenine dinucleotide|FAD]] at their N-terminus while others are unable to bind FAD. It is understood that this is the case because the N-terminal fold is a region known to bind FAD as a needed [[Cofactor (biochemistry)|cofactor]]. Also curious is that FAD plays no observed role in active site [[Redox|oxidation-reduction reactions]] of this enzyme.<ref name=":0" /> Those HNLs that bind FAD do so at a [[Hydrophobic effect|hydrophobic]] region neighboring the active site where it is believed that the binding of FAD confers structural stability that allows for enzymatic action. These HNL, referred to as HNL Class I (or HNL I) are also noted to have N-terminus [[glycosylation]] and the distinct heterogeneity and presence of isoforms within the same organism. HNL Class II (HNL II), on the other hand, afford a wider variety of substrates, and in general favor (S) [[stereochemistry]], whereas HNL I [[Enantioselective synthesis|stereo-selectively]] produce (R)-mandelonitrile.<ref name=":0" />


==Structure and Action==
==Structure and action==


Due to the simple [[Protein purification|purification]] of this enzyme (5-30 fold purification is sufficient to reach homogeneity), its biological and biochemical analysis have been very thoroughly studied.<ref name=":0" /> In addition to the study of many [[Protein isoform|isoforms]] within a given organism, there has been study dedicated to the understanding of HNL [[Protein localization|localization]], the physical structure of the enzyme and its active site, and the mechanisms by which it is able to mediate this important set of reactions. Upon the purification of [[Prunus serotina|Black Cherry]] HNL, research from Wu and Poulton <ref name=":3">Wu, H., & Poulton, J. E. (1991). Immunocytochemical Localization of Mandelonitrile Lyase in Mature Black Cherry (Prunus serotina Ehrh.) Seeds. ''Plant Physiology,'' ''96''(4), 1329-1337. doi:10.1104/pp.96.4.1329</ref> raised [[antiserum]] to these specific HNL, which were then applied (with [[colloidal gold]] particles in tow) to Black Cherry [[cotyledon]] and [[endosperm]]. Here it was found that HNL overwhelmingly localizes to the cell walls of these developing plants.<ref name=":3" /> It was so enriched in these regions that it was noted upwards of 5% of the [[Cell wall|cell wal]]<nowiki/>l images taken via [[Electron microscope|Electron Microscopy]] imaged the gold particles that were indirectly [[Immunolabeling|labelling]] these proteins.<ref name=":3" />
Due to the simple [[Protein purification|purification]] of this enzyme (5-30 fold purification is sufficient to reach homogeneity), its biological and biochemical analysis have been very thoroughly studied.<ref name=":0" /> In addition to the study of many [[Protein isoform|isoforms]] within a given organism, there has been study dedicated to the understanding of HNL [[Protein localization|localization]], the physical structure of the enzyme and its active site, and the mechanisms by which it is able to mediate this important set of reactions. Upon the purification of [[Prunus serotina|Black Cherry]] HNL, research from Wu and Poulton <ref name=":3">Wu, H., & Poulton, J. E. (1991). Immunocytochemical Localization of Mandelonitrile Lyase in Mature Black Cherry (Prunus serotina Ehrh.) Seeds. ''Plant Physiology,'' ''96''(4), 1329-1337. doi:10.1104/pp.96.4.1329</ref> raised [[antiserum]] to these specific HNL, which were then applied (with [[colloidal gold]] particles in tow) to Black Cherry [[cotyledon]] and [[endosperm]]. Here it was found that HNL overwhelmingly localizes to the cell walls of these developing plants.<ref name=":3" /> It was so enriched in these regions that it was noted upwards of 5% of the [[Cell wall|cell wal]]<nowiki/>l images taken via [[Electron microscope|Electron Microscopy]] imaged the gold particles that were indirectly [[Immunolabeling|labelling]] these proteins.<ref name=":3" />


Knowing where this protein is highly localized, Figure 1 details work that highlights the structure of this protein and the residues in its active site respectively. Of specific interest, HNLs make use of a catalytically active [[Cysteine|Cys]] residue.<ref name=":1" /> While [[Cysteine]] residues are conserved throughout species in three separate locations (at the [[N-terminus|N-terminal]] FAD binding site, and two at the [[C-terminus|C-terminal]] active site), it appears that the catalytically active residue lies near the active site, suggesting an important role in HNL catalytic action. Other structural features indicative of HNL are split based off of their class. While Class II HNL are known to be more heterogenous and more often seen in [[grain]]<nowiki/>s, Class I HNL are more typically FAD-binding and function as [[Seed|seed storage proteins]]. This action allows for increased [[amino acid metabolism]] in developing seeds. Because the enzyme is able to quickly reverse this reaction to create [[hydrogen cyanide]], HNLs play an essential role in defense of the seed<ref name=":2" /><ref name=":0" />
Knowing where this protein is highly localized, Figure 1 details work that highlights the structure of this protein and the residues in its active site respectively. Of specific interest, HNLs make use of a catalytically active [[Cysteine|Cys]] residue.<ref name=":1" /> While [[Cysteine]] residues are conserved throughout species in three separate locations (at the [[N-terminus|N-terminal]] FAD binding site, and two at the [[C-terminus|C-terminal]] active site), it appears that the catalytically active residue lies near the active site, suggesting an important role in HNL catalytic action. Other structural features indicative of HNL are split based on their class. While Class II HNL are known to be more heterogenous and more often seen in [[grain]]<nowiki/>s, Class I HNL are more typically FAD-binding and function as [[Seed|seed storage proteins]]. This action allows for increased [[amino acid metabolism]] in developing seeds. Because the enzyme is able to quickly reverse this reaction to create [[hydrogen cyanide]], HNLs play an essential role in defense of the seed<ref name=":2" /><ref name=":0" />


As of late 2007, only one [[tertiary structure|structure]] has been solved for this class of enzymes, with the [[Protein Data Bank|PDB]] accession code {{PDB link|1JU2}}.
As of late 2007, only one [[tertiary structure|structure]] has been solved for this class of enzymes, with the [[Protein Data Bank|PDB]] accession code {{PDB link|1JU2}}.


== Mechanism of Action ==
== Mechanism of action ==
[[File:Synthetic Cyanohydrin Pathway.jpg|thumb|356x356px|Figure 2: The general organic chemistry synthetic pathway for mandelonitrile. <ref>Corson, B. B.; Dodge, R. A.; Harris, S. A.; Yeaw, J. S. (1941). "Mandelic Acid". Organic Syntheses.; Collective Volume, 1, p. 336</ref>]]
[[File:Synthetic Cyanohydrin Pathway.jpg|thumb|356x356px|Figure 2: The general organic chemistry synthetic pathway for mandelonitrile. <ref>Corson, B. B.; Dodge, R. A.; Harris, S. A.; Yeaw, J. S. (1941). "Mandelic Acid". Organic Syntheses.; Collective Volume, 1, p. 336</ref>]]
<br />
<br />
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HNLs are known to be [[Stereospecificity|stereospecific]], giving the action of this enzyme a major advantage in effectively creating [[Precursor (chemistry)|precursor]]s essential to the metabolic development of [[amino acid]]s and a wide range of clinically relevant small molecules. The wide variety of organisms and isoforms that constitute the HNL family however, has been determined to yield a variety of different [[Mechanism of action|mechanisms]] that facilitate this reaction in a [[Stereospecificity|stereospecific]] way. Figures 2 and 3 detail the typical [[Chemical synthesis|synthetic]] and solved biochemical mechanisms for the formation of this key metabolic intermediate. Key differences between these pathways rely mostly on the lack of [[Enantiomer|enantiomeric specificity]] conferred through the synthetic pathways despite the use of similar classes of [[Chemical reaction|reactions]]. In addition, most of the synthetic methods for facilitating this set of reactions take place in [[organic solvent]], whereas it has been shown that HNL activity is highest at a [[Emulsion|polar-nonpolar interface]].<ref name=":0" /><ref name=":4">Wehtje, E., Adlercreutz, P., & Mattiasson, B. (1990). Formation of C-C bonds by mandelonitrile lyase in organic solvents. ''Biotechnology and Bioengineering,'' ''36''(1), 39-46. doi:10.1002/bit.260360106</ref>
HNLs are known to be [[Stereospecificity|stereospecific]], giving the action of this enzyme a major advantage in effectively creating [[Precursor (chemistry)|precursor]]s essential to the metabolic development of [[amino acid]]s and a wide range of clinically relevant small molecules. The wide variety of organisms and isoforms that constitute the HNL family however, has been determined to yield a variety of different [[Mechanism of action|mechanisms]] that facilitate this reaction in a [[Stereospecificity|stereospecific]] way. Figures 2 and 3 detail the typical [[Chemical synthesis|synthetic]] and solved biochemical mechanisms for the formation of this key metabolic intermediate. Key differences between these pathways rely mostly on the lack of [[Enantiomer|enantiomeric specificity]] conferred through the synthetic pathways despite the use of similar classes of [[Chemical reaction|reactions]]. In addition, most of the synthetic methods for facilitating this set of reactions take place in [[organic solvent]], whereas it has been shown that HNL activity is highest at a [[Emulsion|polar-nonpolar interface]].<ref name=":0" /><ref name=":4">Wehtje, E., Adlercreutz, P., & Mattiasson, B. (1990). Formation of C-C bonds by mandelonitrile lyase in organic solvents. ''Biotechnology and Bioengineering,'' ''36''(1), 39-46. doi:10.1002/bit.260360106</ref>


== Disease Relevance ==
== Disease relevance ==
HNLs and the action they mediate is a key target for study of [[Protein engineering|protein engineering]], as the formation of mandelonitrile is a key step in a wide variety of organic syntheses with medical and therapeutic potential. The step mediated by these enzymes is essential to the synthesis of [[Stereospecificity|stereospecific]] [[Bond Formation|bond formation]] in (R)-Salbutamol [[Bronchodilator|bronchodilators]]<ref name=":5">Effenberger F., Jager J. Synthesis of the adregenergic bronchodilators (R)-terbutaline and (R)-salbutamol from (R)-cyanohydrins. J. Org. Chem. 1997; 62:3867-3873</ref>, (S)-[[Amphetamine|amphetamines]]<ref name=":5" />, (1R, 2S)-(-)-[[ephedrine]] bronchodilators<ref>Jackson WR., Jacob HA., Matthew BR., Jayatilake GS., Watson KG. Stereoselctive syntheses of ephedrine and related 2-aminoalcohols of high optical purity from protected cyanohydrins. Tetrahedron Lett. 1990; 31:1447-1450</ref>, in addition to many others, including [[Lipitor]]<ref>Maureen AR. Biocatalysis buzz, deals underscore interest in biotechnology-based methods to improve chemical processes. Chem Eng News 2002; 80:86</ref>, [[Thalidomide]]<ref>Ziegler T., Horsch B., Effenberger F., A convenient route to (R)-α-hydroxy carboxylic acids and (2R)-1-amin-2-alkanols from (R)-cyanohydrins. Synthesis 1990:575-578.</ref>, and the semi-synthesis of [[cephalosporin]] [[Antibiotic|antibiotics]].<ref>Menendez E., Brieva R., Rebolledo F., Gotor V. Optically active (S) ketone and (R) cyanohydrins via an (R)-oxynitrilase catalyzed transformation chemoenzymatic synthesis of 2-cyanotetrahydrofuran and 2-cyanotetrahydropyran. J Chem Soc, Chem Commun. 1995:989-990</ref> The importance of these mandelonitrile synthons makes the HNL class of enzymes a major target for controlled [[catalysis]] that has been optimized through work at the interface of polar and non-polar solvent conditions.<ref name=":0" /><ref name=":4" />
HNLs and the action they mediate is a key target for study of [[Protein engineering|protein engineering]], as the formation of mandelonitrile is a key step in a wide variety of organic syntheses with medical and therapeutic potential. The step mediated by these enzymes is essential to the synthesis of [[Stereospecificity|stereospecific]] [[Bond Formation|bond formation]] in (R)-Salbutamol [[Bronchodilator|bronchodilators]]<ref name=":5">Effenberger F., Jager J. Synthesis of the adregenergic bronchodilators (R)-terbutaline and (R)-salbutamol from (R)-cyanohydrins. J. Org. Chem. 1997; 62:3867-3873</ref>, (S)-[[Amphetamine|amphetamines]]<ref name=":5" />, (1R, 2S)-(-)-[[ephedrine]] bronchodilators<ref>Jackson WR., Jacob HA., Matthew BR., Jayatilake GS., Watson KG. Stereoselctive syntheses of ephedrine and related 2-aminoalcohols of high optical purity from protected cyanohydrins. Tetrahedron Lett. 1990; 31:1447-1450</ref>, in addition to many others, including [[Lipitor]]<ref>Maureen AR. Biocatalysis buzz, deals underscore interest in biotechnology-based methods to improve chemical processes. Chem Eng News 2002; 80:86</ref>, [[Thalidomide]]<ref>Ziegler T., Horsch B., Effenberger F., A convenient route to (R)-α-hydroxy carboxylic acids and (2R)-1-amin-2-alkanols from (R)-cyanohydrins. Synthesis 1990:575-578.</ref>, and the semi-synthesis of [[cephalosporin]] [[Antibiotic|antibiotics]].<ref>Menendez E., Brieva R., Rebolledo F., Gotor V. Optically active (S) ketone and (R) cyanohydrins via an (R)-oxynitrilase catalyzed transformation chemoenzymatic synthesis of 2-cyanotetrahydrofuran and 2-cyanotetrahydropyran. J Chem Soc, Chem Commun. 1995:989-990</ref> The importance of these mandelonitrile synthons makes the HNL class of enzymes a major target for controlled [[catalysis]] that has been optimized through work at the interface of polar and non-polar solvent conditions.<ref name=":0" /><ref name=":4" />


Revision as of 17:11, 28 March 2019

mandelonitrile lyase
Identifiers
EC no.4.1.2.10
CAS no.9024-43-5
Databases
IntEnzIntEnz view
BRENDABRENDA entry
ExPASyNiceZyme view
KEGGKEGG entry
MetaCycmetabolic pathway
PRIAMprofile
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Gene OntologyAmiGO / QuickGO
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Figure 1: Model of mandelonitrile lyase based on PDB entry 1JU2

In enzymology, a mandelonitrile lyase (EC 4.1.2.10, (R)-HNL, (R)-oxynitrilase, (R)-hydroxynitrile lyase) is an enzyme that catalyzes the chemical reaction

mandelonitrile hydrogen cyanide + benzaldehyde

Hence, this enzyme has one substrate, mandelonitrile, and two products, hydrogen cyanide and benzaldehyde.

This enzyme belongs to the family of lyases, specifically the aldehyde-lyases, which cleave carbon-carbon bonds. The systematic name of this enzyme class is mandelonitrile benzaldehyde-lyase (hydrogen cyanide-forming). Other names in common use include hydroxynitrile lyase, (R)-oxynitrilase, oxynitrilase, D-oxynitrilase, D-alpha-hydroxynitrile lyase, and mandelonitrile benzaldehyde-lyase. This enzyme participates in cyanoamino acid metabolism. It has 2 cofactors: flavin, and flavoprotein.

Historical perspective

Mandelonitrile lyases, more colloquially referred to as HNLs (hydroxynitrile lyases) were first characterized by Wöhler in 1938, based on their high activity in almond.[1] Since then, HNLs have been isolated from a wide variety of plants including stone fruits,[2] sorghum grains,[3] millipedes,[4] and passion fruits.[5]

HNLs are peculiar in that, within the same organism and even the same sample, there exist a variety of different isoforms of this enzyme. These isoforms are not able to be determined from one another based on factors influencing activity.[6] This variety also results from macro-heterogeneity, as some isoforms bind FAD at their N-terminus while others are unable to bind FAD. It is understood that this is the case because the N-terminal fold is a region known to bind FAD as a needed cofactor. Also curious is that FAD plays no observed role in active site oxidation-reduction reactions of this enzyme.[1] Those HNLs that bind FAD do so at a hydrophobic region neighboring the active site where it is believed that the binding of FAD confers structural stability that allows for enzymatic action. These HNL, referred to as HNL Class I (or HNL I) are also noted to have N-terminus glycosylation and the distinct heterogeneity and presence of isoforms within the same organism. HNL Class II (HNL II), on the other hand, afford a wider variety of substrates, and in general favor (S) stereochemistry, whereas HNL I stereo-selectively produce (R)-mandelonitrile.[1]

Structure and action

Due to the simple purification of this enzyme (5-30 fold purification is sufficient to reach homogeneity), its biological and biochemical analysis have been very thoroughly studied.[1] In addition to the study of many isoforms within a given organism, there has been study dedicated to the understanding of HNL localization, the physical structure of the enzyme and its active site, and the mechanisms by which it is able to mediate this important set of reactions. Upon the purification of Black Cherry HNL, research from Wu and Poulton [7] raised antiserum to these specific HNL, which were then applied (with colloidal gold particles in tow) to Black Cherry cotyledon and endosperm. Here it was found that HNL overwhelmingly localizes to the cell walls of these developing plants.[7] It was so enriched in these regions that it was noted upwards of 5% of the cell wall images taken via Electron Microscopy imaged the gold particles that were indirectly labelling these proteins.[7]

Knowing where this protein is highly localized, Figure 1 details work that highlights the structure of this protein and the residues in its active site respectively. Of specific interest, HNLs make use of a catalytically active Cys residue.[5] While Cysteine residues are conserved throughout species in three separate locations (at the N-terminal FAD binding site, and two at the C-terminal active site), it appears that the catalytically active residue lies near the active site, suggesting an important role in HNL catalytic action. Other structural features indicative of HNL are split based on their class. While Class II HNL are known to be more heterogenous and more often seen in grains, Class I HNL are more typically FAD-binding and function as seed storage proteins. This action allows for increased amino acid metabolism in developing seeds. Because the enzyme is able to quickly reverse this reaction to create hydrogen cyanide, HNLs play an essential role in defense of the seed[6][1]

As of late 2007, only one structure has been solved for this class of enzymes, with the PDB accession code 1JU2.

Mechanism of action

Figure 2: The general organic chemistry synthetic pathway for mandelonitrile. [8]


Figure 3: Generalized scheme for the enzymatic cycle and action of HNL. R group indicates a benzene ring. [1][9][10][11][12]

HNLs are known to be stereospecific, giving the action of this enzyme a major advantage in effectively creating precursors essential to the metabolic development of amino acids and a wide range of clinically relevant small molecules. The wide variety of organisms and isoforms that constitute the HNL family however, has been determined to yield a variety of different mechanisms that facilitate this reaction in a stereospecific way. Figures 2 and 3 detail the typical synthetic and solved biochemical mechanisms for the formation of this key metabolic intermediate. Key differences between these pathways rely mostly on the lack of enantiomeric specificity conferred through the synthetic pathways despite the use of similar classes of reactions. In addition, most of the synthetic methods for facilitating this set of reactions take place in organic solvent, whereas it has been shown that HNL activity is highest at a polar-nonpolar interface.[1][13]

Disease relevance

HNLs and the action they mediate is a key target for study of protein engineering, as the formation of mandelonitrile is a key step in a wide variety of organic syntheses with medical and therapeutic potential. The step mediated by these enzymes is essential to the synthesis of stereospecific bond formation in (R)-Salbutamol bronchodilators[14], (S)-amphetamines[14], (1R, 2S)-(-)-ephedrine bronchodilators[15], in addition to many others, including Lipitor[16], Thalidomide[17], and the semi-synthesis of cephalosporin antibiotics.[18] The importance of these mandelonitrile synthons makes the HNL class of enzymes a major target for controlled catalysis that has been optimized through work at the interface of polar and non-polar solvent conditions.[1][13]

References

  1. ^ a b c d e f g h Sharma, Monica; Sharma, Nitya Nand; Bhalla, Tek Chand (August 2005). "Hydroxynitrile lyases: At the interface of biology and chemistry". Enzyme and Microbial Technology. 37 (3): 279–294. doi:10.1016/j.enzmictec.2005.04.013.
  2. ^ Yemm RS, Poulton JE (1986). "Isolation and characterization of multiple forms of mandelonitrile lyase from mature black cherry (Prunus serotina Ehrh.) seeds". Arch. Biochem. Biophys. 247 (2): 440–5. doi:10.1016/0003-9861(86)90604-1. PMID 3717954.
  3. ^ Bovti, C., AND CONN, E. E. (1961) J. Bid Cfiem 236,207-210.
  4. ^ Dadashipour, M., Ishida, Y., Yamamoto, K., & Asano, Y. (2015). Discovery and molecular and biocatalytic properties of hydroxynitrile lyase from an invasive millipede,Chamberlinius hualienensis. Proceedings of the National Academy of Sciences, 112(34), 10605-10610. doi:10.1073/pnas.1508311112Motojima,
  5. ^ a b F. , Nuylert, A. and Asano, Y. (2018), The crystal structure and catalytic mechanism of hydroxynitrile lyase from passion fruit, Passiflora edulis. FEBS J, 285: 313-324. doi:10.1111/febs.14339
  6. ^ a b Hu Z, Poulton JE. Molecular analysis of (R)-(+)-mandelonitrile lyase microheterogeneity in black cherry. Plant Physiol. 1999;119(4):1535-46.
  7. ^ a b c Wu, H., & Poulton, J. E. (1991). Immunocytochemical Localization of Mandelonitrile Lyase in Mature Black Cherry (Prunus serotina Ehrh.) Seeds. Plant Physiology, 96(4), 1329-1337. doi:10.1104/pp.96.4.1329
  8. ^ Corson, B. B.; Dodge, R. A.; Harris, S. A.; Yeaw, J. S. (1941). "Mandelic Acid". Organic Syntheses.; Collective Volume, 1, p. 336
  9. ^ Gruber K. Elucidation of the mode of substrate binding to hydroxynitrile lyase from Hevea brasiliensis. Proteins 2001; 44:26-31.
  10. ^ Dreveny I., Kratky C., Gruber K. The active site of hydroxynitrile layase from Prunus amydalus, modelling studies provide new insights into the mechanism of cyanogenesis. Protein Sci. 2002; 11:293-300
  11. ^ Lauble H., Miehlich B., Forster S., Wajant H., Effenberger F. Crystal Structure of hydroxynitrile lyase from Sorghum bicolor in complez with inhibitor benzoic acid, a novel cyanogenic enzyme. Biochemistry 2002; 41:12043-12050
  12. ^ Lauble H., Miehlich B., Forster S., Wajant H., Effenberger F. . Mechanistic aspects of cyanogensis from active site mutant Ser80Ala of hydroxynitrile lyase for Manihot escuelenta in complex with acetone cyanohydrin. Protein Sci. 2001;10:1015-1022.
  13. ^ a b Wehtje, E., Adlercreutz, P., & Mattiasson, B. (1990). Formation of C-C bonds by mandelonitrile lyase in organic solvents. Biotechnology and Bioengineering, 36(1), 39-46. doi:10.1002/bit.260360106
  14. ^ a b Effenberger F., Jager J. Synthesis of the adregenergic bronchodilators (R)-terbutaline and (R)-salbutamol from (R)-cyanohydrins. J. Org. Chem. 1997; 62:3867-3873
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External links

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