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1yb6

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[[Image:1yb6.gif|left|200px]]
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{{STRUCTURE_1yb6| PDB=1yb6 | SCENE= }}
{{STRUCTURE_1yb6| PDB=1yb6 | SCENE= }}
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'''Hydroxynitrile lyase from hevea brasiliensis in complex with mandelonitrile'''
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===Hydroxynitrile lyase from hevea brasiliensis in complex with mandelonitrile===
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==Overview==
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The hydroxynitrile lyase from the tropical rubber tree Hevea brasiliensis (HbHNL) is utilized as a biocatalyst in stereospecific syntheses of alpha-hydroxynitriles from aldehydes and methyl-ketones. The catalyzed reaction represents one of the few industrially relevant examples of enzyme mediated C-C coupling reactions. In this work, we determined the X-ray crystal structures (at 1.54 and 1.76 Angstroms resolution) of HbHNL complexes with two chiral substrates -- mandelonitrile and 2,3-dimethyl-2-hydroxy-butyronitrile -- by soaking and rapid freeze quenching techniques. This is the first structural observation of the complex between a HNL and chiral substrates. Consistent with the known selectivity of the enzyme, only the S-enantiomers of the two substrates were observed in the active site. The binding modes of the chiral substrates were identical to that observed for the biological substrate acetone cyanohydrin. This indicates that the transformation of these non-natural substrates follows the same mechanism. A large hydrophobic pocket was identified in the active site of HbHNL which accommodates the more voluminous substituents of the two substrates. A three-point binding mode of the substrates -- hydrophobic pocket, hydrogen bonds between the hydroxyl group and Ser80 and Thr11, electrostatic interaction of the cyano group with Lys236 -- offers a likely structural explanation for the enantioselectivity of the enzyme. The structural data rationalize the observed (S)-enantioselectivity and form the basis for modifying the stereospecificity through rational design. The structures also revealed the necessity of considerable flexibility of the sidechain of Trp128 in order to bind and transform larger substrates.
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(as it appears on PubMed at http://www.pubmed.gov), where 17250917 is the PubMed ID number.
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{{ABSTRACT_PUBMED_17250917}}
==About this Structure==
==About this Structure==
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[[Category: Catalytic triad]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 15:08:13 2008''

Revision as of 12:08, 29 July 2008

Image:1yb6.png

Template:STRUCTURE 1yb6

Hydroxynitrile lyase from hevea brasiliensis in complex with mandelonitrile

Template:ABSTRACT PUBMED 17250917

About this Structure

1YB6 is a Single protein structure of sequence from Hevea brasiliensis. Full crystallographic information is available from OCA.

Reference

Structural determinants of the enantioselectivity of the hydroxynitrile lyase from Hevea brasiliensis., Gartler G, Kratky C, Gruber K, J Biotechnol. 2007 Mar 30;129(1):87-97. Epub 2006 Dec 17. PMID:17250917

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