Philipson K D, Nishimoto A Y
Am J Physiol. 1982 Sep;243(3):C191-5. doi: 10.1152/ajpcell.1982.243.3.C191.
The Na+-Ca2+ exchange activity of purified canine cardiac sarcolemmal vesicles can be strikingly stimulated if the vesicles are pretreated with a serine or thiol proteinase. The Km (Ca2+) for Na+i-dependent Ca2+ influx is reduced from 22.2 +/- 2.3 to 8.1 +/- 0.3 microM while Vmax is increased from 15.1 +/- 3.6 to 18.9 +/- 5.2 nmol Ca2+ . mg protein-1 . s-1. Na+o-dependent Ca2+ efflux is also stimulated by proteinase pretreatment although passive (Na+-independent) Ca2+ efflux from the sarcolemmal vesicles is unaffected. Proteinase treatment reduces the sensitivity of Na+-Ca2+ exchange to the inhibitors chlorpromazine and polymyxin B, but not to the inhibitor, palmitylcarnitine. Using a newly developed technique we are able to demonstrate that the Na+-Ca2+ exchange of inside-out sarcolemmal vesicles is being stimulated by proteinase treatment (Philipson, K. D., and A. Y. Nishimoto, J. Biol. Chem: 257, 5111-5117, 1982; this technique uses the ATP-dependent Na+ pump to preload only inside-out vesicles with Na+ prior to Na+-Ca2+ exchange). Right-side-out vesicles may also be stimulated.
如果用丝氨酸或巯基蛋白酶对纯化的犬心肌肌膜囊泡进行预处理，其钠钙交换活性会受到显著刺激。钠依赖的钙内流的米氏常数（Km[Ca2+]）从22.2±2.3微摩尔降至8.1±0.3微摩尔，而最大反应速度（Vmax）从15.1±3.6增加至18.9±5.2纳摩尔钙·毫克蛋白-1·秒-1。蛋白酶预处理也会刺激钠依赖的钙外流，尽管肌膜囊泡的被动（非钠依赖）钙外流不受影响。蛋白酶处理降低了钠钙交换对抑制剂氯丙嗪和多粘菌素B的敏感性，但对抑制剂棕榈酰肉碱不敏感。使用一种新开发的技术，我们能够证明蛋白酶处理会刺激内翻肌膜囊泡的钠钙交换（菲利普森，K.D.，和A.Y.西本莫托，《生物化学杂志》：257，5111 - 5117，1982；该技术在进行钠钙交换之前，利用ATP依赖的钠泵仅向内翻囊泡预加载钠）。外翻囊泡也可能受到刺激。
