Ribokinase (RBKS)

All metabolic sugars are phosphorylated to trap them inside the cell and to prepare them for further chemical reactions. Ribokinase (EC 2.7.1.15) phosphorylates ribose, an essential sugar in nucleotide biosynthesis. Although D-ribose is not generally effective as a sole carbon source for cultured animal cells, ribose-utilizing strains have been isolated. Ribose-utilizing variants of the rat Novikoff hepatoma cell line show changes in ribokinase activity. Jargiello (1982) found that parental and some variant Novikoff cells had 3 peaks of ribokinase activity, during S, G2, and M phase. In contrast, variants with high basal levels of ribokinase had only 1 peak of enzyme activity, during S phase. Ribokinase activity was either soluble or membrane-associated, and the subcellular localization differed between cell strains.