Bishop G A, Rozenberg M C
Biochim Biophys Acta. 1975 Mar 28;384(1):112-9. doi: 10.1016/0005-2744(75)90100-x.
A protein phosphokinase (ATP: protein phosphotransferase EC 2.7.1.37) which is stimulated by 3',5'-cyclic adenosine monophosphate (cyclic AMP) has been partially purified from both the cytoplasmic and membrane fractions of human platelets. The kinetics of both enzymes preparations are similar in respect to cyclic AMP, ATP, ADP and AMP. 5-10-minus 7 M cyclic AMP stimulated both preparations by approximately 100%. Both ADP and AMP at a concentration of 5-10-minus 5 M inhibited protein phosphokinase activity of the soluble and membrane preparation by between 50% and 70%. The response of the two enzyme preparations to calcium differed. 10 mM Ca-2+ inhibited soluble protein phosphokinase activity approximately 80% both in the presence and absence of 5-10 minus 7 M cyclic AMP whereas the same concentrations of Ca-2+ inhibited the membrane-bound enzyme by approximately 60% in the presence of 5-10-minus 7 M cyclic AMP and 40% in the absence of cyclic AMP. This observation may be of importance in understanding the mechanism of platelet aggregation.
一种受3',5'-环磷酸腺苷（环磷酸腺苷）刺激的蛋白磷酸激酶（ATP：蛋白磷酸转移酶EC 2.7.1.37）已从人血小板的细胞质和膜部分中部分纯化出来。两种酶制剂在环磷酸腺苷、ATP、ADP和AMP方面的动力学相似。5×10⁻⁷M的环磷酸腺苷使两种制剂的活性均提高了约100%。浓度为5×10⁻⁵M的ADP和AMP均可使可溶性和膜制剂的蛋白磷酸激酶活性抑制50%至70%。两种酶制剂对钙的反应不同。在存在和不存在5×10⁻⁷M环磷酸腺苷的情况下，10mM Ca²⁺均可使可溶性蛋白磷酸激酶活性抑制约80%，而在存在5×10⁻⁷M环磷酸腺苷时，相同浓度的Ca²⁺可使膜结合酶活性抑制约60%，在不存在环磷酸腺苷时抑制约40%。这一观察结果可能对理解血小板聚集机制具有重要意义。
