OCCURRENCE OF INOSINE KINASE AS A DISTINCT ENZYME IN SPIRULINA-PLATENSIS

Among a series of purine nucleosides, inosine was found to be phosphor ylated at the highest rate by crude extracts of the cyanobacterium Spi rulina platensis. The inosine phosphorylating activity could be separa ted from hypoxanthine-guanine phosphoribosyl transferase. This result shows that IMP formation may occur via the direct phosphorylation of i nosine at its 5'-position, rather than via inosine phosphorolysis, fol lowed by hypoxanthine phosphoribosylation, and provides unequivocal ev idence for the occurrence of inosine kinase in nature. (C) 1995 Academ ic Press. Inc.