Studies on the Enzymic Reduction of Amino Acids

Glycine can be employed by a number of anaerobic bacteria as the electron acceptor in a coupled oxidation-reduction reaction between pairs of amino acids (a Stickland reaction).This process (Reaction 1) involves a reductive deamination of glycine to form acetic acid and ammonia (1).Until recently, little information was available concerning the mechanism of glycine reduction in such a fermentation since earlier attempts to study it in extracts had met with failure (2).It became possible to examine this reaction in some detail in enzyme preparations derived from Cloatridium sticklandii (3) when it was discovered that dimercaptans such as DMP' would function as electron donors (4).The reduction of glycine in this system has proved to be an unexpectedly complex process which results in the formation of ATP (5).The partial purification and some of the properties of this glycine reductase system of C. sticklandii are described in the present communication. MaterialsAcetyl kinase was prepared from Escherichia wli according to the procedure of Rose et al. (6).Purified phosphotransacetylase was obtained from E. R. Stadtman.Reduced lipoic acid and redistilled BAL were gifts from I. C. Gun&us and H. Tabor, respectively.DMP was synthesized according to the method of Stocken (7).Glycine-l-C14 was purchased from the Volk Radiochemical Company, glycine 2-C" from the Nuclear ENZYMIC REDUCTION OF AMINO ACIDS.III