Induction of D-galactonate dehydratase in Mycobacterium butyricum

The induced synthesis of D-galactonate dehydratase in Mycobacterium butyricum has been studied initially after addition or removal of inductor or inhibitor. The enzyme was induced by galactonate and galactose; the system reached half-maximal effect of synthesis at 3.3 mM of galactonate. The lag of about 30 min between the addition of the inductor and the appearance of the enzyme at 37 degrees C was noted. The lag was dependent on temperature and independent of inductor concentration. After the withdrawal of the inductor the expression of a supposed galactonate dehydratase-coding messenger takes place which can be blocked by streptomycin or chloramphenicol. Both the messenger (the mean life of about 38 min) and the enzyme appeared relatively stable. The enzyme synthesis was found to be under strong catabolite repression caused by glucose and several other compounds and cyclic AMP failed to increase the enzyme synthesis or to overcome the repression. Zinc ions at concentration below 1 mM proved to have no effect on the enzyme synthesis but inhibited the enzyme itself that can be restored by EDTA.