Digestive activity of lysosomes. I. The digestion of proteins by extracts of rat liver lysosomes.
Digestive activity of lysosomes. I. The digestion of proteins by extracts of rat liver lysosomes.
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发表时间：
1968-06
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通讯作者：
J. Coffey;C. D. Duve
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作者：
J. Coffey;C. D. Duve
本文研究了大鼠肝溶酶体消化各种脂质的能力。从用Triton WR-1339处理的大鼠的肝脏中分离溶酶体，并且基本上不含其他细胞组分。当在37° C下在0.1 M醋酸盐缓冲液（pH 4.3 - 4.6）中与这些底物孵育时，它们能够使磷脂酰胆碱、磷脂酰乙醇胺、磷脂酰丝氨酸、磷脂酰肌醇、溶血磷脂酰胆碱、溶血磷脂酰乙醇胺、磷脂酸、心磷脂、三棕榈酸甘油酯、1，2-二棕榈酸甘油酯、1，3-二棕榈酸甘油酯和1-二棕榈酸甘油酯广泛脱酰。对于大多数底物，在不添加去污剂的情况下发生水解。三棕榈酸甘油酯，其在没有去污剂的情况下不被攻击，但在5%Triton X-100的存在下被剧烈地脱酰化，以及心磷脂，其需要添加0.1%Triton X-100以在乙酸盐缓冲液中水解，但在不添加去污剂的柠檬酸盐缓冲液中被攻击。甘油二酯的水解由5%Triton X-100刺激。另一方面，这种洗涤剂抑制磷脂酰乙醇胺和棕榈酸甘油酯的脱酰作用。鞘磷脂不脱酰，但水解为神经酰胺和磷酸胆碱。在各种条件下，用溶酶体或全肝制剂均不能建立神经酰胺的水解。从消化磷脂产生的磷酸二酯被证明是耐溶酶体水解，无论是在酸性和碱性pH值。一个碱性磷酸二酯酶作用于甘油磷酸胆碱是存在于整个肝脏。这种活性的一部分位于细胞液中;其余部分分布在细胞核和微粒体组分之间，其方式提示定位在质膜中。发现溶酶体具有使磷脂酸、α-甘油磷酸以及胆碱、乙醇胺和丝氨酸的磷酸单酯脱磷酸的能力，尽管速度相当缓慢。微粒体和线粒体的脂质和蛋白质的广泛消化发生在这些细胞组分与纯化的溶酶体在pH 4.3下长时间孵育后。RNA在这些条件下似乎被分解。因此，很明显，溶酶体可以完成重要的消化功能。然而，从颗粒中清除该过程的一些产物，特别是磷酸二酯的方式引起了生理重要性的问题。
Abstract The ability of rat liver lysosomes to digest various lipids has been investigated. The lysosomes were isolated from the livers of rats treated with Triton WR-1339 and were essentially free of other cell components. They were able to deacylate extensively phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, lysophosphatidylcholine, lysophosphatidylethanolamine, phosphatidic acid, cardiolipin, tripalmitin, 1,2-dipalmitin, 1,3-dipalmitin, and 1-monopalmitin, when incubated with these substrates at 37° in 0.1 m acetate buffer, pH 4.3 to 4.6. With most substrates, hydrolysis occurred without the addition of a detergent. Exceptions were tripalmitin, which was not attacked in the absence of detergent, but was deacylated vigorously in the presence of 5% Triton X-100, and cardiolipin, which required addition of 0.1% Triton X-100 for hydrolysis in acetate buffer, but was attacked in citrate buffer without added detergent. The hydrolysis of diglycerides was stimulated by 5% Triton X-100. On the other hand, this detergent inhibited the deacylation of phosphatidylethanolamine and of monopalmitin. Sphingomyelin was not deacylated, but was hydrolyzed to ceramide and phosphorylcholine. Hydrolysis of ceramide could not be established, either with lysosomes or with whole liver preparations, under a variety of conditions. The phosphodiesters arising from the digestion of phospholipids proved to be resistant to lysosomal hydrolysis, both at acid and alkaline pH. An alkaline phosphodiesterase acting on glycerophosphorylcholine is present in whole liver. Part of this activity is located in the cell sap; the remainder is distributed between the nuclear and microsomal fractions in a manner suggestive of a localization in the plasma membrane. The lysosomes were found to have the ability to dephosphorylate phosphatidic acid, α-glycerophosphate, and, although rather slowly, the phosphomonoesters of choline, ethanolamine, and serine. Extensive digestion of the lipids and proteins of both microsomes and mitochondria occurs upon prolonged incubation of these cell components with purified lysosomes at pH 4.3. RNA appears to be broken down under these conditions. Thus it is clear that lysosomes can accomplish the important digestive functions with which they are credited. However, the manner in which some of the products of this process, especially the phosphodiesters, are cleared from the particles raises a problem of physiological importance.