Some properties of a basic L-amino-acid oxidase from Anacystis nidulans

An L-amino acid oxidase (L-amino-acid oxygen oxidoreductase (deaminating), EC 1.4.3.2) from the blue-green alga Anacystis nidulans has been purified to homogeneity with an overall yield of about 10%. Purification included ammonium sulfate fractionation and CM-Sephadex, DEAE-Sephadex, and hydroxyapatite chromatography. The purified enzyme has an absorption spectrum which is characteristic of a flavoprotein, and contains 1 mol FAD per mol enzyme. The native enzyme has a molecular weight of 98 000 as determined by gel exclusion chromatography. Electrophoresis in SDS-polyacrylamide gels gives a single protein band corresponding to a molecular weight of 49 000, which suggests that the native enzyme is composed of 2 subunits of equal molecular weight. As previously demonstrated, the enzyme catalyzes the oxidative deamination of the basic amino acids: L-arginine, L-lysine, L-ornithine and L-histidine. In the presence of catalase and of any of these amino acids, 0.5 mol O2 is consumed, and 1 mol ammonia is formed for each mol amino acid oxidized. HCN is formed from L-histidine when the L-amino acid oxidase is supplemented with peroxidase. In addition to the unusual substrate specificity of this L-amino acid ozidase, it also has an unusual set of inhibitors including o-phenanthroline as well as divalent cations of which Cu2+, Zn2+, and Cd2+ are the most effective ones, but Mg2+ and Ca2+ also inhibit. This inhibition can be reversed by chelating agents such as EDTA. ATP and ADP, but not AMP, can also overcome the inhibition caused by Mg2+, for example. The inhibitory effect of cations can be demonstrated in vivo.