Induction of Enzymes Involved in the Catabolism of Deoxyribonucleosides and Ribonucleosides in <i>Escherichia coli</i> K 12

Abstract

When cells of Escherichia coli are grown in the presence of deoxyribonucleosides with glucose or glycerol as carbon sources the following enzymes are induced: deoxyriboaldolase, thymidine phosphorylase, deoxyribomutase, and purine nucleoside phosphorylase. Experiments with mutants deficient in one of the enzymes support the conclusion that formation of deoxyribose‐5‐phosphate is required for this induction. Two of these enzymes, deoxyribomutase and purine nucleoside phosphorylase, are also induced in the presence of purine ribonucleosides. Evidence is presented that in this case phosphorolysis of the added purine nucleosides is not required for induction and, furthermore, that adenosine gives rise to induction only after prior deamination to inosine. Addition of adenosine to glycerol‐grown cells of strains deficient in purine nucleoside phosphorylase, gives rise to an unspecific induction of nucleoside catabolizing enzymes in general.