Evidence against the involvement of adenosine 3′,5′-cyclic monophosphate in glucose inhibition of β-galactosidase induction in Bacillus megaterium

Abstract

When B. megaterium cells are grown on D-galactose as the sole C source, the cells actively synthesize .beta.-galactosidase (.beta.-D-galactoside galactohydrolase, EC 3.2.1.23). D-Galactose, when added to a glucose-grown culture, did not induce .beta.-galactosidase, apparently because of the glucose inhibition of galactose transport. When glucose was added to a galactose-grown culture, the transport of galactose continued at a reduced but significant rate, but further synthesis of .beta.-galactosidase was halted. Cyclic[c]AMP or cGMP did not relieve the glucose inhibition of .beta.-galactosidase synthesis in the preinduced culture. A method which gave a reproducible assay of c[32P]AMP in Escherichia coli did not detect cAMP or cGMP in a B. megaterium culture undergoing .beta.-galactosidase induction, but revealed the extracellular accumulation of 2 unknown phosphorylated compounds. Cell-free extracts prepare from galactose-grown cells did not catalyze the degradation of cAMP or cGMP.