ISSN:
0899-0042
Schlagwort(e):
substrate enantioselectivity
;
product enantioselectivity
;
chirality
;
activation enthalpy
;
activation entropy
;
chiral HPLC
;
Chemistry
;
Organic Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
The steady-state kinetic parameters for pig liver carboxylesterase (PLE)-catalyzed hydrolysis of the prochiral substrate dimethyl phenylmalonate (DMPM) (product enantioselectivity) and the separate enantiomers of three chiral 2-phenylpropionic acid esters (substrate enantioselectivity) were measured at seven temperatures between 288 K and 312 K. Arrhenius plots of turnover numbers against the reciprocal of experimental temperatures yielded enthalpies and entropies of activation at enzyme saturation. (+)-(S)-methyl-2-phenylpropionate, (+)-(S)-4-nitrophenyl 2-phenylpropionate, and both enantiomers of phenyl 2-phenylpropionate showed very similar activation enthalpies and entropies (approximately 50 kJ mol-1 and -50 J mol-1 K-1, respectively), but differences were observed for (-)-(R)-methyl 2-phenylpropionate and (-)-(R)-4-nitrophenyl 2-phenylpropionate. Whereas the entropies of activation of all 2-phenylpropionates were negative, positive entropies of activation were measured in the formation of monomethyl phenylmalonate enantiomers from DMPM. Enthalpy-entropy compensation analysis of the data indicates a common mechanism of PLE substrate and product enantiospecificity in the reactions studied here. © 1994 Wiley-Liss, Inc.
Zusätzliches Material:
4 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/chir.530060105
