| Popis: |
Chromatographic, electrophoretic and spectrophotometric techniques have been combined and applied to extracts from hog-kidney cortices to isolate, purify, and identify a rather stable preparation of histaminase which appears to be homogeneous by the criteria of chromatography and analytical electrophoresis. In a large number of electrophoretic runs evidence has been obtained that histaminase travels as a single, distinct band at pH values above 5.2 towards the anode to be located in the region between α 2 - and β-globulin fractions of normal human serum. No migration of histaminase has been observed between the pH values 5.0 and 5.15 which may signify the location of the isoelectric point of histaminase. The electrophoretically pure histaminase has been found to be free from contamination with diamine oxidase. It acts specifically on histamine and on its ring-N substituted derivatives such as 1-methyl-4-(β-aminoethyl)imidazole (1,4-methylhistamine) and 1-methyl-5-(β-aminoethyl)imidazole (1,5-methylhistamine) as substrates, but has no effect whatsoever on diamines such as putrescine, cadaverine, or hexamethylene diamine, typical substrates of diamine oxidase. The finding that histamine and 1,4-methylhistamine are both degraded by the same enzyme, histaminase, seems to add to the biological significance of histaminase in view of Schayer's contention that 1,4-methylhistamine is one of the main metabolites of histamine degradation in vivo . Results of spectrophotometric, fluorometric, and chemical investigations of the pure enzyme point to the presence in the histaminase molecule of two prosthetic groups, FAD and pyridoxal phosphate. The reaction mechanism as well as the significance of these findings are discussed. |
