|Siddiqui JA, Shoeb SA, Hoshina Y, Noda Y, Shimizu E, Karasawa D, Yorifuji D
|Histamine: Pyruvate aminotransferase from Pseudomonas aureofaciens IFO 3521
|J Biochem Mol Biol Biophys
|Pseudomonas aureofaciens IFO 3521 (ATCC 13985) belonging to the Gram-negative purple group of bacteria possesses an histamine degrading enzyme, histamine aminotransferase (HMAT), which transfer amino group of histamine to pyruvate to yield imidazole acetaldehyde and L-alanine. The HMAT activity was detected in the extract of the cells grown on histamine containing medium, but not in the extracts of the cells grown on medium of L-asparagine, imidazole and histidine. HMAT of Pseudomonas aureofaciens was partially purified to a specific activity of 1.02 units/mg. HMAT showed its highest activity toward histamine. L-histidine was transaminated at a rate of 68% that of histamine. The enzyme was sensitive to the carbonyl reagent of hydroxylamine and hydrazine. Sulfhydral reagents have no effects on the enzyme. Metal ions, Mn++, Cu++ and Ni++ inhibited the enzyme moderately. The enzyme was most active at pH 8.0 in Tris-hydrochloride buffer and most stable at pH 7.0 in potassium phosphate buffer.