Characterization of an Escherichia coli mutant which utilizes glycerol in the absence of cyclic adenosine monophosphate.

The aerobic catabolism of glycerol depends on the expression of the glpK operon specifying a glycerol kinase and the glpD operon specifying an sn-glycerol-3-phosphate (G3P) dehydrogenase. It has not been clearly established how the expression of these operons is dependent on adenosine 3',5'-cyclic monophosphate (cAMP). We have isolated a promoterlike mutant (CA8306B) which, owing to a mutation in the glpK operon, can utilize glycerol in the absence of cAMP. Glycerol kinase and G3P dehydrogenase are inducible in CA8306B and its wild-type parent CA8000. The induced level of glycerol kinase in CA8306B is 30% that of CA8000 and this level is increased fivefold by the addition of cAMP. However, the induced level of G3P dehydrogenase in CA8306B is similar to that of CA8000 and is unaffected by cAMP addition. These results suggest that the promotion of the glpK operon requires cAMP whereas the promotion of the glpD operon does not.