The Active Site of Plasma Amine Oxidase “The Key Enzyme of Biogenic Amines Degradation in Plasma” as Seen by Fluorescence Investigations

Abstract

The role of Plasma Amine Oxidase (diamino: O₂ oxidoreductase; EC 1.4.3.6) in the catabolism of various amines found in association with DNA and its function in one of the catabolic pathways of histamine and other pharmacologically important amines have led to considerable interest in this enzyme. The enzyme catalyzes the oxidation of certain amines and diamines according to the following reaction:

$$RC{H_2}N{H_2} + {O_2} + {H_2}O - - - - - RCHO + N{H_3} + {H_2}{O_2}$$

Physicochemical studies of bovine plasma amine oxidase indicated that the enzyme is made up of two identical subunits and has a molecular weight of 170,000 KD (Yasunobu et al., 1976). The enzyme contains one essential histidine residue per monomer (Hiramatsu, et al., 1975). There are two gram-atom Cu/ mole protein which are essential for enzyme activity (Yasunobu et al., 1976). It has been reported that the copper does not change its valence state during catalysis either under aerobic or anaerobic addition of substrate. The only variance to the no valence change was the work reported by Mondovi et al., 1976 who reported that copper changed its valence state during substrate oxidation. It was concluded acid analysis was performed on the native enzyme and the reduced modified enzyme. The concentration of the protein was determined by a biuret method and absorbance was read at 280nm (R = 13). N-(1-pyrene) maleimide was purchased from Molecular Probes. The other common reagents used were of reagent grade and were purchased from standard companies.