COMPETITIVE-INHIBITION OF LENS-CULINARIS L. COPPER AMINE OXIDASE BY AMILORIDE, P-AMINOBENZAMIDINE, CLONIDINE, 4',6-DIAMIDINO-2-PHENYLINDOLEAND GABEXATE MESYLATE - A COMPARATIVE-STUDY

The competitive inhibition of Lens culinaris,is L. copper amine oxidas e by amiloride (K-i = 4.1 x 10(-4) M), p-aminobenzamidine (K-i = 6.0 x 10(-4) M), clonidine (K-i = 5.0 x 10(-4) M), 4',6-diamidino-2-phenyli ndole (DAPI; K-i = 1.9 x 10(-5) M) and gabexate mesylate (K-i = 2.5 x 10(-4) M) has been investigated, at pH 7.0 and 25 degrees C. The affin ity of p-aminobenzamidine, clonidine and DAPI for plant and mammalian copper amine oxidase is closely similar. However, values of K-i for am iloride and gebexate mesylate binding to swine kidney copper amine oxi dase are lower than those observed for inhibitor binding to Lens culin aris L. copper amine oxidase. Thus, amiloride and gabexate mesylate ma y represent useful model compounds for the development of selective in hibitors of mammalian copper amine oxidase, which may be important in view of the potential use of plant copper amine oxidase as drugs.