Kinetic studies with the use of proton-magnetic-resonance spectroscopy of the specific alpha-deuteration of amino acids by Escherichia coli aspartate aminotransferase. |
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Authors: | E Gout S Chesne C G Beguin and J Pelmont |
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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. |
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