title: Cleaving of S-mandelonitrile catalyzed by S-hydroxynitrile lyase from Hevea brasiliensis--a kinetic investigation based on the rate curve method.
abstract: The progress curves of conversion of racemic-mandelonitrile (R-MN) at different concentrations to benzaldehyde (BA) and hydrogen cyanide (HCN), catalyzed by S-hydroxynitrile lyase from Hevea brasiliensis, together with the enantiomeric excess curves of R-MN are converted into individual progress curves of the S- and R-enantiomers. They reveal that, under the prevailing experimental conditions, the non-enzymatic conversion is sufficiently slow compared to its enzyme-catalyzed counterpart, so that it can be ignored in a simplified analysis. Tikhonov regularization is then used to convert the progress curves of the S-enantiomer into reaction rate curves. These curves are used to determine the rate constants in the rate expression based on a three-step reversible ordered Uni-Bi reaction scheme that describes this enzyme-catalyzed reaction. The resulting rate constants are compared against published data. Some of the problems encountered and their solution are briefly discussed.
authors.affiliation: Department of Chemical and Biomolecular Engineering, The University of Melbourne, Melbourne, Vic., Australia. yly@unimelb.edu.au
authors.forename: Y Leong
authors.initials: YL
authors.lastname: Yeow
authors.forename: Yee-Kwong
authors.initials: YK
authors.lastname: Leong
authors.forename: Mee Yean
authors.initials: MY
authors.lastname: Cheah
authors.forename: Huong D T
authors.initials: HD
authors.lastname: Dang
authors.forename: Connie K P
authors.initials: CK
authors.lastname: Law
mesh_terms: D000097:Acetonitriles / Q000737:chemistry*; D000446:Aldehyde-Lyases / Q000737:chemistry*; D000465:Algorithms; D001547:Benzaldehydes / Q000138:chemical synthesis*; D002384:Catalysis; D003198:Computer Simulation; D004789:Enzyme Activation; D028482:Hevea / Q000201:enzymology*; D006856:Hydrogen Cyanide / Q000138:chemical synthesis*; D007536:Isomerism; D007700:Kinetics; D008956:Models, Chemical; D009716:Numerical Analysis, Computer-Assisted; D013379:Substrate Specificity
chemical_list: D000097:Acetonitriles; D001547:Benzaldehydes; D006856:Hydrogen Cyanide; C045516:mandelonitrile; D000446:Aldehyde-Lyases; C496044:S-hydroxynitrile lyase, Hevea brasiliensis; C032175:benzaldehyde