期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1988
卷号：85
期号：20
页码：7541-7545
DOI：10.1073/pnas.85.20.7541
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Rabbit serum is shown to contain a cAMP-dependent protein kinase (biochemically characterized as type II) that specifically phosphorylates a 135-kDa endogenous protein. This endogenous phosphorylation can be reproduced with platelet-rich plasma, after stimulation with thrombin, but not with plasma devoid of platelets. Stimulation of isolated platelets ("washed" by gel filtration) with either thrombin or ADP brings about a release of this kinase. The supernatant of these stimulated platelets, which contains the kinase, does not undergo a cAMP-dependent endogenous phosphorylation because it does not contain the 135-kDa protein substrate. On the other hand, plasma devoid of platelets does not contain cAMP-dependent protein kinase. By combining the supernatant of the physiologically stimulated platelets with the plasma devoid of platelets, it is possible to reconstitute the system and to reproduce the specific endogenous phosphorylation of the 135-kDa target substrate. On the basis of the above evidence it is proposed that upon physiological stimulation of platelets, they release into the blood a cAMP-dependent protein kinase in addition to the well-known release of MgATP. This kinase specifically phosphorylates the 135-kDa plasma protein.
