REVERSAL OF THE CA2+ PUMP OF BLOOD-PLATELETS

被引:19
作者
BENECH, JC [1 ]
WOLOSKER, H [1 ]
DEMEIS, L [1 ]
机构
[1] UNIV FED RIO DE JANEIRO, INST CIENCIAS BIOMED, DEPT BIOQUIM, BR-21941590 RIO DE JANEIRO, RJ, BRAZIL
关键词
D O I
10.1042/bj3060035
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
In this study, the endoplasmic Ca2+ transport ATPase of blood platelets was compared with Ca2+ ATPase of sarcoplasmic reticulum skeletal muscle. Similar to the muscle enzyme, the Ca2+ ATPase from platelets was found to catalyse ATP reversible arrow P-i exchange both in the presence and in the absence of a transmembrane Ca2+ gradient. When platelet vesicles are loaded with Ca2+ and diluted in medium containing ADP, P-i and EGTA, the ATPase catalyses Ca2+ efflux coupled to synthesis of ATP. The stoichiometry between Ca2+ ion released and ATP synthesized by platelet Ca2+ ATPase is 1, while that of skeletal muscle is 2. Thapsigargin, a specific inhibitor of sarcoplasmic/endoplasmic reticulum Ca2+ ATPases, inhibited both the Ca2+-dependent ATPase activity and the reversal of the platelet Ca2+ pump. The possibility is discussed that the differences observed between the two transport systems is related to the distinct amino acid sequences of the enzymes.
引用
收藏
页码:35 / 38
页数:4
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