Purification and properties of the l-amino acid oxidase from monocellate cobra ( Naja naja kaouthia) venom

Abstract

1. 1. The l-amino acid oxidase of the monocellate cobra ( Naja naja kaouthia) venom was purified to electrophoretic homogeneity. The molecular weight of the enzyme was 112,200 as determined by Sephadex G-200 gel filtration chromatography, and 57,400 as determined by SDS-polyacrylamide gel electrophoresis. 2. 2. The enzyme had an isoelectric point of 8.12 and a pH optimum of 8.5. It showed remarkable thermal stability, and, unlike many venom l-amino acid oxidase, was also stable in alkaline medium. The enzyme was partially inactivated by freezing. 3. 3. The enzyme was very active against l-phenylalanine and l-tyrosine, moderately active against l-tryptophan, l-methionine, l-leucine, l-norleucine, l-arginine and l-norvaline. Other l-amino acids were oxidized slowly or not oxidized. 4. 4. Kinetic studies suggest the presence of a side-chain bincling site in the enzyme, and that the bincling site comprises of at least four hydrophobic subsites.