Lentrichia B B, Bruner W E, Kean E L
Invest Ophthalmol Vis Sci. 1978 Sep;17(9):884-95.
The pH optima and apparent Km and Vmax values were determined for nine glycosidases of the retinal pigment epithelium (RPE) of the calf. In terms of micromoles of substrate cleaved per milligram protein per hour, the following relative order of enzymatic activities was observed: beta-N-acetylglucosaminidase greater than alpha-glucosidase = beta-N-acetylgalactosaminidase greater than alpha-mannosidase greater than beta-galactosidase greater than beta-glucosidase greater than alpha-fucosidase greater than alpha-galactosidase greater than beta-glucuronidase. The pH optimum of each of these enzymes was in the acidic range (below pH 6). All these findings refer to enzymatic activities of bovine RPE preparations obtained by the brushing procedure of Glocklin and Potts and washing as described by Berman and Feeney. Thus they may relate to those activities associated with particulate components of the RPE cell and not to the more soluble glycosidases. The distribution of the glycosidases between the washes of the cells and the final pellet of bovine RPE cells was examined. The activities of 10 glycosidases in the RPE of the embryonic chick were also examined. Neither beta-mannosidase nor beta-fucosidase activities could be detected in washed bovine RPE cells, although beta-mannosidase was detected in RPE of the embryonic chick. The presence of isoenzymes of beta-glucuronidase in bovine RPE was indicated. Specificity by beta-glucuronidase of bovine RPE for synthetic substrates was observed.
测定了小牛视网膜色素上皮（RPE）的九种糖苷酶的最适pH值以及表观Km和Vmax值。以每毫克蛋白质每小时裂解的底物微摩尔数计算，观察到以下酶活性的相对顺序：β-N-乙酰氨基葡萄糖苷酶＞α-葡萄糖苷酶 = β-N-乙酰半乳糖苷酶＞α-甘露糖苷酶＞β-半乳糖苷酶＞β-葡萄糖苷酶＞α-岩藻糖苷酶＞α-半乳糖苷酶＞β-葡萄糖醛酸苷酶。这些酶各自的最适pH值均在酸性范围内（pH值低于6）。所有这些发现均涉及通过Glocklin和Potts的刷洗程序以及Berman和Feeney所述的洗涤方法获得的牛RPE制剂的酶活性。因此，它们可能与RPE细胞的颗粒成分相关的活性有关，而与更易溶解的糖苷酶无关。研究了糖苷酶在牛RPE细胞洗涤液和最终沉淀之间的分布。还检测了胚胎鸡RPE中10种糖苷酶的活性。在洗涤后的牛RPE细胞中未检测到β-甘露糖苷酶和β-岩藻糖苷酶的活性，尽管在胚胎鸡的RPE中检测到了β-甘露糖苷酶。表明牛RPE中存在β-葡萄糖醛酸苷酶的同工酶。观察到牛RPE的β-葡萄糖醛酸苷酶对合成底物的特异性。
