Substrate specificity of king cobra ( Ophiophagus hannah) VENOM l-amino acid oxidase

Abstract

1. 1. Substrate specificity of purified king cobra ( Ophiophagus hannah) venom l-amino acid oxidase was investigated. 2. 2. The enzyme was highly specific for the l-enantiomer of amino acid. Effective oxidation of l-amino acid by the enzyme requires the presence of a free primary α-amino group but the α-carboxylate group is not as critical for the catalysis. 3. 3. The enzyme was very active against l-Lys, l-Phe, l-Leu, l-Tyr, l-Tryp, l-Arg, l-Met, l-ornithine, l-norleucine and l-norvaline and moderately active against l-His, l-cystine and l-Ileu. Other l-amino acids were oxidized slowly or not oxidized. 4. 4. The data suggest the presence of a side chain binding site in the enzyme, and that the binding site comprises at least five ‘subsites’: the hydrophobic subsites a, b and c; and the two ‘amino’ binding subsites d and e. Subsite b appears to be able to accommodate two methylene/methyl carbons.