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D-Alanine Oxidase from Escherichia coli: Participation in the Oxidation of L-Alanine

^a Department of Chemistry, Indiana University, Bloomington, Indiana 47401

ABSTRACT

Cell wall-membrane preparations of Escherichia coli, prepared by the ethylenediaminetetraacetic acid-lysozyme method, contain enzymes which catalyze the oxidation of D-alanine and, to a lesser extent, L-alanine into pyruvate and ammonia without the formation of hydrogen peroxide. The kinetic parameters were (i) pH optima of 8.3 to 8.4 for L- and D-alanine and (ii) a K_m value of 6.6 ± 0.2 mM for D-alanine. Several coenzymes were without effect when added to the reaction mixture. The participation of D-alanine oxidase in the oxidation of L-alanine was demonstrated. The evidence is based on (i) results of cellular fractionation; (ii) labeling experiments; (iii) inhibition studies with aminooxyacetate and cycloserine; (iv) denaturation experiments; and (v) demonstration of the presence of an active racemase.

¹ Present address: Department of Biochemistry, University of Turku, 20500 Turku 50, Finland.

² Present address: Department of Biochemistry, University of North Carolina, Chapel Hill, N.C. 27514.