Pilistine S J, Varandani P T
Mol Cell Endocrinol. 1986 Jun;46(1):43-52. doi: 10.1016/0303-7207(86)90068-7.
The susceptibility of porcine relaxin and 125I-polytyrosyl-porcine relaxin to degradation by 3 purified enzymes involved in the degradation of insulin and proinsulin was examined. Rat liver glutathione-insulin transhydrogenase (GIT), which cleaves disulfide bonds in insulin, catalyzed a time- and concentration-dependent increase in trichloroacetic acid (TCA)-soluble radioactivity of relaxin. The Sephadex G-50 profile of the reaction products revealed conversion to the A- and B-chains. Relaxin competitively inhibited the degradation of insulin by GIT; however, kinetic analysis revealed insulin to be preferred over relaxin as a substrate. Rat liver cytosol neutral thiol peptidase (NTP) catalyzed a time- and concentration-dependent increase in the TCA solubility of relaxin and a shift in the Sephadex G-50 radioactivity profile to low molecular weight products. Kinetic analysis revealed that insulin and B-chain are preferred over relaxin as substrates for NTP. A third enzyme, rat kidney neutral metalloendopeptidase, which degrades proinsulin and insulin C-peptide but not insulin, also did not degrade porcine relaxin.
研究了猪松弛素和125I-聚酪氨酰猪松弛素对参与胰岛素和胰岛素原降解的3种纯化酶降解作用的敏感性。大鼠肝脏谷胱甘肽-胰岛素转氢酶（GIT）可裂解胰岛素中的二硫键，催化松弛素的三氯乙酸（TCA）可溶性放射性随时间和浓度依赖性增加。反应产物的葡聚糖凝胶G-50图谱显示其转化为A链和B链。松弛素竞争性抑制GIT对胰岛素的降解；然而，动力学分析表明，胰岛素作为底物比松弛素更受青睐。大鼠肝脏胞质溶胶中性硫醇肽酶（NTP）催化松弛素的TCA溶解度随时间和浓度依赖性增加，且葡聚糖凝胶G-50放射性图谱向低分子量产物偏移。动力学分析表明，胰岛素和B链作为NTP的底物比松弛素更受青睐。第三种酶，大鼠肾脏中性金属内肽酶，可降解胰岛素原和胰岛素C肽，但不能降解胰岛素，也不能降解猪松弛素。
