Modelling of L-DOPA enzymatic oxidation catalyzed by L-amino acid oxidases from Crotalus adamanteus and Rhodococcus opacus

L-amino acid oxidases (L-AAO) are well known for their broad substrate specificity. L-amino acid oxidases from Crotalus adamanteus and Rhodococcus opacus were applied for biotransformation of 3,4-dihydroxyphenyl-L-alanine (L-DOPA) as a substrate to its corresponding alpha-keto acid. In this reaction, hydrogen peroxide formed as a by-product causes chemical decarboxylation of alpha-keto acids and acts as competitive product inhibitor. Beef liver catalase was used to decompose it.It was shown that both enzymes were able to oxidize L-DOPA to corresponding products. L-AAO from R. opacus was more specific (lower K I-DOPA value) and more active towards L-DOPA substrate than L-AAO from C. adamanteus. Its catalytic constant, k(3), estimated by Levenspiel's method, was found to be 10-fold higher than the one for L-AAO from C adamanteus. L-AAO from R. opacus exhibits slightly L-DOPA inhibition, which is not the case for L-AAO from C adamanteus.The biotransformations Of L-DOPA were carried out in batch enzyme membrane reactor (EMR), as well as in the repetitive batch EMR. The reactor and kinetics were modelled. Parameters were estimated by differential and integral method and presented in this article. (c) 2005 Elsevier B.V. All rights reserved