title: Partial purification and characterization of histidine acetyltransferase in brain of Nile tilapia (Oreochromis niloticus).
abstract: High activity of histidine acetyltransferase (HISAT) was found in the brain and the lens of Nile tilapia Oreochromis niloticus. HISAT was semi-purified 4166-fold from the brain of Nile tilapia. The affinity chromatography using a Blue Sepharose 6 FF column was very effective for purification of this enzyme. The enzyme had a broad pH optimum from pH 7.0 to pH 9.5, and did not require any divalent metal ion. The semi-purified HISAT showed a strict substrate specificity for L-histidine (and its methyl derivatives) and acetylcoenzyme A (CoASAc). The reaction velocity fits normal Michaelis-Menten kinetics with respect to both L-histidine (Km, 0.45 mM) and CoASAc (Km, 0.027 mM). Gel filtration on Superdex 200 HR indicated the molecular weight of 39,000. It was presumed that the 38.5 kDa protein, which was intensely visualized in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was a single subunit derived from HISAT.
mesh_terms: D000105:Acetyl Coenzyme A / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006639:Histidine / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008970:Molecular Weight; D013379:Substrate Specificity; D013696:Temperature; D017210:Tilapia
chemical_list: D004791:Enzyme Inhibitors; D006639:Histidine; D000105:Acetyl Coenzyme A