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Initiation of Spore Germination in Bacillus subtilis: Relationship to Inhibition of L-Alanine Metabolism

^a Laboratory of Molecular Biology, National Institute of Neurological Diseases and Stroke, Bethesda, Maryland 20014

ABSTRACT

The inhibitory effects of anthranilic acid esters (methyl anthranilate and N-methyl anthranilate) on the L-alanine-induced initiation of spore germination was examined in Bacillus subtilis 168. Methyl anthranilate irreversibly inhibited alanine initiation by a competitive mechanism. In its presence, the inhibition could be reversed only by the combined addition of D-glucose, D-fructose, and K⁺. Both L-alanine dehydrogenase and L-glutamate-pyruvate transaminase, enzymes which catalyze the first reaction in L-alanine metabolism, were competitively inhibited by methyl anthranilate. The K_i values for germination initiation (0.053 mM) and of L-glutamate-pyruvate transaminase (0.068 mM) were similar, whereas that for L-alanine dehydrogenase (0.4 mM) was six to seven times higher. Since a mutant lacking L-alanine dehydrogenase activity germinated normally in L-alanine alone, it is speculated that the major pathway of L-alanine metabolism during initiation may be via transmination reaction.

¹ Present address: Laboratory of Biochemical Genetics, National Heart and Lung Institute, Bethesda, Md. 20014.