Chen C H, Chen S C
Biochemistry Laboratory, Wilmer Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Arch Biochem Biophys. 1988 May 1;262(2):427-38. doi: 10.1016/0003-9861(88)90394-3.
A study of subcellular acid phosphatase distribution in mammalian tissues shows that isozymes with specific functions are compartmentalized in the cells. The enzyme may be generalized into two types: type A and type B. They are shown by several means to be distinct entities. Type A is confined to the cytoplasm and is inhibited by Cu2+, HCHO, and the coupling agents (for enzyme staining) fast blue RR salt and fast Garnet GBC salt (newly discovered inhibitors), but is insensitive to fluoride and L-(+)-tartrate. Type B is localized in the organelles, presumably lysosomes, in both soluble form and membrane-bound form, with inhibitor sensitivity exactly opposite to that of type A enzyme. Types A and B consist of different sets of isozymes, with sensitivities to inhibitors resembling those observed with the crude extracts of subcellular fractions. Acid phosphatase that exhibits a phosphoryl transfer property was identified as type A enzyme. Type A enzyme has a slightly higher optimal pH and is inhibited by alloxan, whereas for type B, the addition of alloxan broadens the optimal pH to a higher range and elevates the activity of pH 7.4 from negligible to about 30-40% of that obtained under optimal conditions. The alloxan-mediated elevation of type B enzyme activity to this level at the physiological pH may be of considerable significance. Type B enzyme has a high affinity for metabolic intermediates and nucleotides, while type A has an extremely low affinity for these substrates. Cytoplasmic acid phosphatase (type A) is a significant enzyme population and its activity is not related to the lysosome density in the cells. Type A enzyme in the cytoplasm is thus shown to be an entity distinctly different from type B enzyme in the lysosomes. These findings suggest that the physiological functions of type A acid phosphatase, such as metabolic regulatory processes, merit further studies because of the phosphoryl transfer activity and cytoplasmic localization of the enzyme.
一项关于哺乳动物组织中亚细胞酸性磷酸酶分布的研究表明，具有特定功能的同工酶在细胞内是分隔分布的。该酶可大致分为两类：A 型和 B 型。通过多种方法表明它们是不同的实体。A 型局限于细胞质，受到 Cu2+、HCHO 以及（用于酶染色的）偶联剂固蓝 RR 盐和固红 GBC 盐（新发现的抑制剂）的抑制，但对氟化物和 L-(+)-酒石酸盐不敏感。B 型定位于细胞器中，可能是溶酶体，以可溶形式和膜结合形式存在，其抑制剂敏感性与 A 型酶完全相反。A 型和 B 型由不同的同工酶组组成，对抑制剂的敏感性与亚细胞组分粗提物中观察到的相似。表现出磷酸转移特性的酸性磷酸酶被鉴定为 A 型酶。A 型酶的最佳 pH 略高，受到四氧嘧啶的抑制，而对于 B 型，添加四氧嘧啶会将最佳 pH 拓宽到更高范围，并将 pH 7.4 时的活性从可忽略不计提高到最佳条件下获得的活性的约 30 - 40%。在生理 pH 下，四氧嘧啶介导的 B 型酶活性升高到这一水平可能具有相当重要的意义。B 型酶对代谢中间体和核苷酸具有高亲和力，而 A 型对这些底物的亲和力极低。细胞质酸性磷酸酶（A 型）是一个重要的酶群体，其活性与细胞中的溶酶体密度无关。因此，细胞质中的 A 型酶被证明是与溶酶体中的 B 型酶明显不同的实体。这些发现表明，由于 A 型酸性磷酸酶的磷酸转移活性和细胞质定位，其生理功能如代谢调节过程值得进一步研究。
