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.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error