fulltext.study @t Gmail

Structural determinants of the enantioselectivity of the hydroxynitrile lyase from Hevea brasiliensis

Paper ID Volume ID Publish Year Pages File Format Full-Text
25256 43563 2007 11 PDF Available
Title
Structural determinants of the enantioselectivity of the hydroxynitrile lyase from Hevea brasiliensis
Abstract

The hydroxynitrile lyase from the tropical rubber tree Hevea brasiliensis (HbHNL) is utilized as a biocatalyst in stereospecific syntheses of α-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 Å 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.

Keywords
Cyanogenesis; C–C bond formation; Crystal structure analysis; Complexes with chiral substrates; Stereospecificity
First Page Preview
Structural determinants of the enantioselectivity of the hydroxynitrile lyase from Hevea brasiliensis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us
Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Biotechnology - Volume 129, Issue 1, 30 March 2007, Pages 87–97
Authors
, , ,
Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us