PH-substrate relationship of l-amino acid oxidases from snake venom and rat kidney

Abstract

l-amino acid oxidase (l-amino acid: O2 oxidoreductase (deaminating), E.C. 1.4.3.2) from Crotalus adamanteus venom exhibits six different shapes of pH-curves depending on the amino acids used as substrate. Basic amino acids such as l-lysine, δ-hydroxy-l-lysine and l-ornithine were oxidized at a high rate when the pH was favorable. The characteristics of the substituent groups on the ε-amino radical of l-lysine determined the shape of pH-curve, the rate of oxidation and optimum pH for this enzyme. With rat kidney oxidase, the effect of l-amino acids on both the pH-curve and the optimum pH was not as evident as with the snake venom enzyme. Finally, it was observed that certain amino acids could protect these enzymes from inactivation at high alkaline pH.