Evidence for interacting catalytic sites of human platelet monoamine oxidase

Summary Studies with human platelet monoamine oxidase show that the enzyme contains two interacting catalytic sites. One site has a high affinity for phenylethylamine and its activity is noncompetitively inhibited by either benzylamine or tryptamine. However, benzylamine and tryptamine act as fully competitive inhibitors for each other and thus appear to be deaminated as a separate site. The Km for each amine was in good agreement with the KI determined when it was used as an inhibitor.