Oxypurine and 6-thiopurine nucleoside triphosphate formation in human erythrocytes

A variety of oxypurines and 6-thiopurines could be transformed by intact erythrocytes to their nucleoside triphosphate forms when incubations were extended for up to 24 hrs. The specific nucleotide monophosphate kinases which accomplish these reactions in erythrocytes were not identified but their ability to utilize 6-thioIMP, 6-thioXMP and 6-methylthioGMP as substrates, albeit very slowly, is clearly implied by these results. S-methylation of 6-thiopurines was demonstrated in erythrocytes incubated with physiological amounts of methionine-(CH3-3H). 6-Methylthioguanosine triphosphate and 6-methylmercaptopurine riboside triphosphate were formed in micromolar amounts, probably from the corresponding thiopurine nucleotides by methyl transfer from S-adenosylmethionine.