Amino acid resolution was studied in this paper. L-Methionine and DL-methionine were used as substrates for the two snake venom L-amino acid oxidases (from Crotalus adamanteus and Crotalus atrox). Even though these enzymes have similar background, they exhibit differences as well as similarities. It was found that both enzymes are active towards L-methionine as substrate (V-m = 0.78 mmol min(-1) g(-1)) and have similar affinities (K-m(L-met) (C. adamanteus) = 0.19 mM, K-m(L-met) (C. atrox) = 0.25 mM). Both enzymes were inhibited in the presence of 2-oxo-4-methylthiobutyric acid (K-i(2-oxo) (C. adamanteus) = 0.83 mM, K-i(2-oxo) (C. atrox) = 2.04 mM), a reaction product of L-methionine oxidative deamination. L-Amino acid oxidase from C atrox was found to be inhibited by the substrate as well. L-Amino acid oxidase from C. adamanteus was inhibited by D-enantiomer of L-methionine (K-i(D-met) = 1.41 mM). Both enzymes were successful in L-methionine oxidation in the batch reactor (100% conversion). This was not the case in the continuously operated enzyme membrane reactor where enzyme deactivation occurred. (C) 2008 Elsevier Ltd. All rights reserved.