Semicarbazide-sensitive amine oxidase inhibitory and hydroxyl radical scavenging activities of aspartic acid β-hydroxamate and glutamic acid γ-monohydroxamate

It was reported that semicarbazide-sensitive amine oxidase (SSAO) in plasma was elevated in diabetes mellitus and heart failure. SSAO catalyzed the oxidative deamination of various amines to produce hydrogen peroxide which is one possible source of oxidative stresses. In this research, two amino acid hydroxamates, namely aspartic acid β-hydroxamate (AAH) and glutamic acid γ-monohydroxamate (GAH), showed dose-dependently inhibitory against SSAO from bovine plasma. The IC₅₀ of AAH and GAH was 0.7 mM and 0.023 mM, respectively, in the comparisons with 0.035 mM of semicarbazide (positive controls). The AAH showed mixed noncompetitive inhibition against bovine SSAO in the respect to benzylamine (substrate) and benzylamine-SSAO (substrate-enzyme complex). It was found that the V'_max value was reduced and K'_m value was increased in the presence of AAH (0.4 mM). Using electron spin resonance to investigate the hydroxyl radical scavenging activities, AAH and GAH showed effectively scavenging activities and IC₅₀ was 0.66 mM and 1.21 mM, respectively.