Incubation of 6-phosphogluconate dehydrogenase from Candida utilis with either acetyl phosphate, 1,3-diphosphoglycerate or carbamoyl phosphate results in the phosphorylation of the protein. The binding of one phosphate residue per enzyme subunit does not affect significantly the kinetic properties, but makes the enzyme less reactive toward thiol reagents, trypsin and pyridoxal 5′-phosphate. We suggest indicate that: (1) 6-phosphogluconate dehydrogenase from C. utilis is phosphorylated non-enzymically by physiological acyl phosphates and (2) the phosphorylation of the enzyme modifies the rate of protein inactivation.
