SEMICARBAZIDE-SENSITIVE AMINE OXIDASE ACTIVITY IN THE HUMAN HEART

A semicarbazide-sensitive amine oxidase with affinity for benzylamine (Bz.SSAO) was found in the human heart, This enzymatic activity has a K-m of 278 +/- 35.3 mu M and a V-m Of 114.7 +/- 14.7 nmol mg(-1) min(- 1) (mean +/- SE of eight hearts) for benzylamine and is strongly inhib ited by 1 mM histamine and by B24, a specific inhibitor of Bz.SSAO, No diamine oxidase activity was found in human heart. The levels of MAO A and B mere assayed: MAO A showed a K-m of 137.1 +/- 16.2 mu M and a V-m of 10.4 +/- 2.5 nmol mg(-1) min(-1) for serotonin; MAO B had a K-m of 9.9 +/- 1.6 mu M and V-m of 4.3 +/- 1.1 nmol mg(-1) min(-1) for be ta-phenylethylamine (mean +/- SE of seven hearts). The human heart has high MAO B activity and Bz.SSAO with histaminase activity. (C) 1998 A cademic Press.