1887

Abstract

Summary: Effects of DL-alanine racemase, D-alanine, heat-activation and ammonia on germination of T spores were studied. Michaelis-Menten parameters for DL-alanine racemase activity in intact spores were: (L-alanine) = 3.6 mM; (D-alanine) = 1.2 mM; (L- to D-alanine) = 1.6 μmol min (mg dry spores); (D- to L-alanine) = 0.53 μmol min (mg dry spores). Racemase activity was irreversibly inhibited with pseudo first order kinetics by incubating intact spores with 10 mM-D-cycloserine. (Aminooxy)acetate (50 μm) completely inhibited racemase activity with 100 mM-L-alanine as substrate. D-Cysteine was a moderately effective racemase inhibitor. Comparisons of the effects of racemase inhibitors, D-alanine and spore concentration on germination rates in 1 mM-L-alanine indicated that racemization of L-alanine accounted for nearly total inhibition of germination at spore concentrations exceeding about 50 μg ml, in the range conventionally used for spectrophotometric germination assays. Heat-activation decreased the inhibitory effect of D-alanine, increasing the germination rate in 2 mM-racemic alanine by a factor of 26. Using spores with an inhibited alanine racemase, germination rates in 1 mM-L-alanine were stimulated by 40 mM-NHCl to an extent comparable to the stimulation obtained by heat-activating the spores. Germination of unactivated spores in 1 mM-L-alanine + 40 mM-NHCl was completely inhibited by 1 mM-D-alanine. These results clarified the roles of D-alanine and DL-alanine racemase in controlling the germination of unactivated spores and suggested that the germinative functions of ammonia and the stereoisomers of alanine may be related.

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/content/journal/micro/10.1099/00221287-130-12-3123
1984-12-01
2019-10-23
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http://instance.metastore.ingenta.com/content/journal/micro/10.1099/00221287-130-12-3123
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