KINETIC-PROPERTIES OF TYPE-II ATP DIPHOSPHOHYDROLASE FROM THE TUNICA MEDIA OF THE BOVINE AORTA

被引:29
作者
COTE, YP [1 ]
OUELLET, S [1 ]
BEAUDOIN, AR [1 ]
机构
[1] UNIV SHERBROOKE,FAC SCI,DEPT BIOL,SHERBROOKE J1K 2R1,QUEBEC,CANADA
关键词
ATP-DIPHOSPHOHYDROLASE; APYRASE; VASCULAR SMOOTH MUSCLE CELL; PURINE NUCLEOTIDE; PLATELET AGGREGATION;
D O I
10.1016/0167-4838(92)90084-Q
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The kinetic properties of type-II ATP diphosphohydrolase are described in this work. The enzyme preparation from the inner layer of the bovine aorta, mostly composed of smooth muscle cells, shows an optimum at pH 7.5. It catalyzes the hydrolysis of tri- and diphosphonucleosides and it requires either Ca2+ or Mg2+ for activity. It is insensitive to ouabain (3 mM), an inhibitor of Na+/K+-ATPase, to tetramisole (5 mM), an inhibitor of alkaline phosphatase, and to Ap5A (100 muM), an inhibitor of adenylate kinase. In contrast, sodium azide (10 mM), a known inhibitor for ATPDases and mitochondrial ATPase, is an effective inhibitor. Mercuric chloride (10 muM) and 5'-p-fluorosulfonylbenzoyl adenosine are also powerful inhibitors, both with ATP and ADP as substrates. The inhibition patterns are similar for ATP and ADP, thereby, supporting the concept of a common catalytic site for these substrates. Apparent K(m) and V(max), obtained with ATP as the substrate, were evaluated at 23 +/- 3 muM and 1.09 mumol P(i)/min per mg protein, respectively. The kinetic properties of this enzyme and its localization as an ectoenzyme on bovine aorta smooth muscle cells suggest that it may play a major role in regulating the relative concentrations of extracellular nucleotides in blood vessels.
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页码:246 / 250
页数:5
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