title: Adenosine kinase from bovine adrenal medulla.
abstract: Adenosine kinase from bovine adrenal medulla was purified 1600-fold by using ammonium sulfate precipitation, gel filtration and affinity chromatography. Gel filtration yielded a relative molecular mass around 42000 and Michaelis constants were 0.2 microM for adenosine and 20 microM for MgATP. The enzyme showed a broad specificity for purine nucleoside triphosphate as phosphate donors. Both free Mg2+ and ATP were inhibitors. AMP was a competitive inhibitor with regard to adenosine and a non-competitive inhibitor versus MgATP, while ADP was a uncompetitive inhibitor with regard to adenosine and a non-competitive inhibitor versus MgATP. Adenosine kinase was strongly inhibited by the bis(adenylyl) polyphosphates Ap4A and Ap5A. These compounds inhibited the enzyme competitively versus MgATP (Ki = 0.06 microM for Ap4A and 0.4 microM for Ap5A) and uncompetitively with regard to adenosine. The results of the kinetic analysis suggest an ordered bi-bi mechanism, adenosine being the first substrate. The phosphorylation of adenosine was unaffected in the presence of vanadate ions.
authors.forename: P
authors.initials: P
authors.lastname: Rotllan
authors.forename: M T
authors.initials: MT
authors.lastname: Miras Portugal
mesh_terms: D000227:Adenine Nucleotides / Q000494:pharmacology; D000241:Adenosine / Q000494:pharmacology; D000248:Adenosine Kinase / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000502:physiology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000313:Adrenal Medulla / Q000201:enzymology*; D000818:Animals; D002417:Cattle; D002846:Chromatography, Affinity; D002855:Chromatography, Thin Layer; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008970:Molecular Weight; D010770:Phosphotransferases / Q000302:isolation & purification*; D013379:Substrate Specificity; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology
chemical_list: D000227:Adenine Nucleotides; D014639:Vanadium; D014638:Vanadates; D000255:Adenosine Triphosphate; D010770:Phosphotransferases; D000248:Adenosine Kinase; D008274:Magnesium; D000241:Adenosine