Guanosine triphosphate: 5-hydroxylysine phosphotransferase in rat kidney cortex

An enzyme which catalyzes the transfer of the gamma-phosphate from GTP onto 5-hydroxylysine was partially purified from rat kidney cortex by means of acid precipitation and DEAE-Sephadex A-50 column chromatography. The enzyme activity was assayed by measuring the transfer of [32P] from gamma-[32P]-GTP to materials not adsorbed by charcoal. This partially purified enzyme showed essentially no GTP phosphohydrolase activity and an optimal pH of 8.0. An apparent Km of about 23.8 mumol/1 was obtained with respect to 5-hydroxylysine. Mg2+ was required for the activity of this enzyme. Ethanolamine, L-lysine, L-ornithine and choline inhibited the enzyme but L-threonine, L-serine and hydroxy-L-proline did not. None of these compounds severed as substrate for this enzyme.