Kinetic aspects involved in the simultaneous enzymatic synthesis of (S)-3-fluoroalanine and (R)-3-fluorolactic acid

Desaminative oxidation of rac-3-fluoroalanine (rac-1) catalyzed by L-alanine dehydrogenase (L-ALADH) was studied by means of initial rate experiments both in the presence and in the absence of a product. Estimates of kinetic parameters of the reaction were obtained. The reaction mechanism is the sequential ordered BiTer mechanism with inhibition by excess of (S)-3-fluoroalanine. This kinetic study was the basis for the development of a couple enzymatic system for the simultaneous synthesis of (S)-3-fluoroalanine (1a) and (R)-3-fluorolactic acid (3) with L-ALADH and L-lactate dehydrogenase using rac-1 and NAD+. Analysis of isolated products revealed la in 60% yield and 86% ee and 3 in 80% yield and over 99% ee. Compounds la and 3 represent chiral building blocks for the synthesis of several products with pharmacological activity. The presence of the fluorine atom in the substrate causes a better interaction of it in the active site of the enzyme. (C) 2003 Elsevier B.V. All rights reserved.