Studies on phosphodeoxyribomutase.

A phosphodeoxyribomutase has been demonstrated in cell-free extracts of Sarcina lutea. The enzyme could be heated to 55 ° for at least 2 h and still retain activity. It had a pH optimum around 7.2, and the most highly purified preparation showed a specific activity of approx. 60 ~moles of deoxyribose 1-phosphate converted to deoxyribose 5-phosphate/mg protein/h. The enzyme was constitutive in the above organism, but could not be demonstrated conclusively in extracts of 14 other microorganisms tested. The enzymic conversion of deoxyribose 1-phosphate to deoxyribose 5-phosphate was established by isolation and enzymic characterization of the product. The enzyme was also able to convert deoxyribose 5-phosphate to pyrimidine-bound deoxyribose, presumably through deoxyribose 1-phosphate. Chromatographic and radiographic studies indicated that, at equilibrium, the reaction contains approx. 95 % deoxyribose 5-phosphate and 5 % deoxyribose 1-phosphate. The mutase was shown to be inhibited by inorganic phosphate at low concentrations, and by deoxyribose 1-phosphate, deoxyribose 5-phosphate, potassium sulfate and fructose 6-phosphate. The enzyme appeared to be stimulated by fructose 1,6diphosphate. The inhibitions by inorganic phosphate and sulfate confirm previous reports in the literature. Acetaldehyde and an aqueous extract of Whatman No. I filter paper were shown to interfere with the cysteine-sulfuric acid reaction with deoxyribose.