猪胰脏中胰岛素拮抗肽的分离纯化及其性质的初步研究

从猪胰脏的酸醇提取液中纯化了一个新的活性多肽——胰岛素拮抗肽,它在整体和细胞水平上对胰岛素都有明显的拮抗作用。猪胰脏的酸醇提取液经CM-52、BioGel P-6、DEAE-52及RP-HPLC纯化后,可得到纯的胰岛素拮抗肽。它能剂量相关地抑制胰岛素在离体大鼠脂肪细胞中的促脂合成活性,抑制50％胰岛素活性时所需的胰岛素拮抗肽为2.0×10~(-10)mol/L与被拮抗的胰岛素剂量在同一水平上。该肽含有较多的碱性氨基酸,分子量的3 000,其N-末端是封闭的。胰岛素拮抗肽的上述理化特征及其对胰岛素的拮抗活性均不同于目前已知的胰脏活性多肽。它对脂肪细胞中胰岛素的拮抗作用可能具有重要的生理意义。

Purification and Preliminary Characterization of a New Peptide-Insulin Antagonist From Porcine Pancreas

A new active peptide has been purified from the acidalcohol extract of porcine pancreas.It markedly suppressed the insulin activity detected either by in vivo mouse convulsion assay or by in vitro free fat cell assay.When the extract was subjected to chromatography on a CM-cellulose column,the insulin fraction completely passed through the column,whereas the glucagon fraction was absorbed.The fact that the total apparent biological activity of insulin in the exclusive eluate was higher than that in the original extract,and that the insulin radioimmunoacti-vity remained unchanged led to the discovery of a potent insulin antagonist in the extract.The antagonist was separated from glucagon and insulin in the extract by ionexchange chromatography on a CM-cellulose column followed by gel filtration on a Bio-Gel P-6 column,and finally purified by reversed-phase HPLC on a C18 column.The antagonistic effect of this peptide on insulin was dose-dependent with ED50 of 2.0*******x10-10mol/L,which was the same level used for insulin in vitro assay(1.7********x10-10 mol/L).Amino acid analysis of the peptide showed that it was rich in Arg and Gly.Its molecular weight was estimated to be about 3000.The N-terminus of the peptide was proved to be blocked as it could not be degraded by Edman degradation.Based on the physicochemical and biochemical characteristics of the insulin antagonist,and compared with other active peptides so far known in pancreas,it is most probably a new active peptide which maybe play an important role in homeostasis of carbohydrate metabolism.