Inhibition of plant and mammalian diamine oxidase by substrate analogues

Imidazoles, aliphatic substrate analogues and the natural dipeptides, carnosine and anserine, were investigated as inhibitors of diamine oxidase from the pig kidney, human pregnancy plasma and pea seedlings. Imidazole, methyli-midazoles,N-acetylimidazole, histamine andN-methyl-histamine are relatively potent inhibitors of mammalian diamine oxidase showing no influence on plant enzymes. Anserine and carnosine are inhibitors of pig kidney and pea seedling enzymes.K₁ values are 2 M and 10 M respectively. Investigated natural derivatives of putrescine and cadaverine have no influence on diamine oxidase of different origin.In conclusion, we present some evidence to suggest that mammalian diamine oxidase, despite a high reaction rate with putrescine, is better adapted to histamine oxidation, whereas for plant enzymes the diamines are preferred substrates.