Studies with GMP synthetase from Ehrlich ascites cells. Purification, properties, and interactions with nucleotide analogs.

摘要: GMP synthetase has been purified 57-fold from Ehrlich ascites cells. The enzyme was found to be stable and have an approximate molecular weight of 85,000 (determined by gel filtration). Its activity stimulated dithiothreitol inhibited 2-mercaptoethanol, p-chloromercuribenzoate, hydroxylamine. Both ammonia glutamine could serve as amino group donors. While none the 10 triphosphate purine pyrimidine nucleotides studied were able substitute for ATP energy donor reaction, all these compounds bind site. Ki values CTP, beta-D-arabinofuranosyl-ATP, 1-N6-ethenoATP slightly lower than Km (0.28 mM). Six monophosphate aminated this enzyme. Listed in order their substrate efficiency (Vmax/Km), they are: xanthosine 5'-phosphate(XMP) (28,000); 2'-dXMP (1,200); 8-azaXMP (320); 6-thioXMP (200); beta-D-arabinofuranosyl-XMP (72); 1-ribosyloxipurinol 5'-phosphate (0.5). 6-ThioXMP a strong alternative inhibitor with 5 muM. products reaction (four studied) competitive inhibitors respect XMP.