title: Kinetic studies with the use of proton-magnetic-resonance spectroscopy of the specific alpha-deuteration of amino acids by Escherichia coli aspartate aminotransferase.
abstract: Escherichia coli aspartate aminotransferase was exposed to aspartate or phenylalanine without oxo acid in buffered 2H2O. The alpha-hydrogen of the amino acids underwent first-order exchange with respect to both substrate and enzyme. P.m.r. spectroscopy gave consistent reaction-rate constants. The deuterium-exchange rate was only moderately increased by addition of oxo acids and was of the same order as the transamination rate. No beta-deuteration was observed. The C(alpha)-H-bond-breaking step is discussed as a part of the entire transamination mechanism.
mesh_terms: D001219:Aspartate Aminotransferases / Q000378:metabolism*; D001224:Aspartic Acid / Q000378:metabolism*; D003903:Deuterium; D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D010649:Phenylalanine / Q000378:metabolism*
chemical_list: D001224:Aspartic Acid; D010649:Phenylalanine; D003903:Deuterium; D001219:Aspartate Aminotransferases