Yamamoto H, Yamada T, Itoh Y
Department of Laboratory Medicine, Jichi Medical School, Minami Kawachi Machi, Tochigi-Ken, Japan.
Clin Chem Lab Med. 2000 Jun;38(6):495-9. doi: 10.1515/CCLM.2000.072.
Instability of beta2-microglobulin in acidic urine was investigated by identifying an associated protease from normal urine. Degradation was completely blocked by pepstatin, an aspartic protease inhibitor, and the counterpart of the inhibitor was thus sought. The molecular weight of the counterpart was similar to that of the inhibitor, while its cleavage site on beta2-microglobulin was identical in three products generated in purified beta2-microglobulin in normal acidified urine (pH 5.0-5.5) and those generated by direct reaction between purified beta2-microglobulin and cathepsin D in acetic acid (pH 5.0). On Western blotting, the presence of cathepsin D was demonstrated immunochemically in urine, and its urinary concentration correlated well with degree of beta2-microglobulin degradation. All these findings strongly suggest that cathepsin D is a major urinary acid protease involved in the degradation of beta2-microglobulin.
通过从正常尿液中鉴定一种相关蛋白酶，研究了β2-微球蛋白在酸性尿液中的稳定性。天冬氨酸蛋白酶抑制剂胃蛋白酶抑制素可完全阻断降解，因此寻找该抑制剂的对应物。该对应物的分子量与抑制剂相似，而其在β2-微球蛋白上的切割位点在正常酸化尿液（pH 5.0 - 5.5）中纯化的β2-微球蛋白产生的三种产物以及在乙酸（pH 5.0）中纯化的β2-微球蛋白与组织蛋白酶D直接反应产生的产物中是相同的。在蛋白质印迹法中，免疫化学证明尿液中存在组织蛋白酶D，其尿液浓度与β2-微球蛋白降解程度密切相关。所有这些发现都有力地表明，组织蛋白酶D是参与β2-微球蛋白降解的主要尿液酸性蛋白酶。
