ISOTOPIC COMPETITION BETWEEND- ANDL-METHIONINE IN ALCALIGENES FECALIS

Abstract

The ability of exogenous D-methionine to prevent the incorporation of exogenous L-methionine into the protein of Alcaligenes fecalis has been studied. D-Methionine has been found to competitively inhibit the ability of the cell to concentrate medium L-methionine with an efficiency of about 14:1. It does not inhibit the incorporation of endogenous methionine into cell protein. D-Methionine is replaceably concentrated by the cell and is able to specifically displace L-methionine previously concentrated by the cell. The significance of these findings for the mechanism of concentration of amino acids by bacteria is discussed.