title: Dephosphorylation of purine mononucleotides by alkaline phosphatases. Substrate specificity and inhibition patterns.
abstract: Three purine mononucleotides, adenosine-, inosine- and guanosine monophosphate, were used as substrates at pH 7.4 and at 10.4 for three alkaline phosphatases (orthophosphoric-monoester phosphohydrolase (acid optimum), EC 3.1.3.1) containing similar phosphate-binding serine groups at their esteratic sites. Substrate specificity was found for the enzymes from calf intestine and bovine liver. Alkaline phosphatase from Escherichia coli was nonspecific. A substrate-dependent and pronounced inhibition with the purine analogue 1,3-dimethyl xanthine was found for the enzymes from intestine and liver, but not for alkaline phosphatase from E. coli. A substrate-independent and pronounced inhibition was found for all three enzymes with the phosphomonoester p-nitrophenol phosphate as the inhibitor. Alkaline phosphatases may play an important role in the regulation of the intracellular content of purine mononucleotides.
mesh_terms: D000249:Adenosine Monophosphate / Q000378:metabolism*; D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D004926:Escherichia coli / Q000201:enzymology; D006150:Guanine Nucleotides / Q000378:metabolism*; D006157:Guanosine Monophosphate / Q000378:metabolism*; D007291:Inosine Monophosphate / Q000378:metabolism*; D007292:Inosine Nucleotides / Q000378:metabolism*; D007422:Intestines / Q000201:enzymology; D008099:Liver / Q000201:enzymology; D009596:Nitrophenols / Q000494:pharmacology; D009943:Organophosphorus Compounds / Q000494:pharmacology; D013379:Substrate Specificity; D013806:Theophylline / Q000494:pharmacology
chemical_list: D006150:Guanine Nucleotides; D007292:Inosine Nucleotides; D009596:Nitrophenols; D009943:Organophosphorus Compounds; D007291:Inosine Monophosphate; D000249:Adenosine Monophosphate; D006157:Guanosine Monophosphate; D013806:Theophylline; D000469:Alkaline Phosphatase