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Insulin-modulating peptide from soybean protein: Identification of the component and the mechanism on biological activity

大豆蛋白胰岛素调节肽：成分鉴定及其生物活性机制

基本信息

批准号：
63480055
负责人：
MAKINO Shio
金额：
$ 3.01万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1989
项目状态：
已结题

项目摘要

Several lines of evidence had indicated that some component(s) of soybean protein participates in the modulation of lipid metabolism and that one of the hormones involved in the metabolism is insulin. We looked for soybean protein component(s) which is capable of affecting the insulin action. By sequencing of purified peptides and examination of their effects on fat decomposition in isolated rat adipocytes, it was confirmed that A_<1a> and A_2 acidic subunits of glycinin potentiate the action of insulin in vitro. In addition, the proteins showed an ability to bind bile acids. Thus, these proteins are probable candidates which exert the hypocholesterolemic effect, a well-known physiological function of soybean protein, by interfering with steroid adsorption. However, the bile acidbinding ability was not related to the insulin-stimulating activity. Both properties were noted in acidic subunits of legumin from pea seed, indicating that these characteristics may be common to legume proteins.Trypsinized products of A_<1a> subunit (A_<1a>/TR) also exhibited the insulin-stimulating activity and the molecular mechanism was examined by using rat adipocytes. A_<1a>/TR did not affect the glucose transport, which is the primary process of insulin action on the cells.However, A_<1a>/TR enhanced a reactivity and a sensitivity of fat decomposition to insulin.Affinity of insulin to its receptor on the cell surface was not affected by A_<1a>/TR. A_<1a>/TR protected insulin from degradation, resulted in an increase of insulin concentration in the cells. The insulin-stimulating activities were not observed at 15ﾟC, indicating that the internarization of insulin is requisite for an appearance of the protein effect, and the inhibition of insulin degradation alone cannot account for the enhancing effect observed in the maximal responses to the hormone.

已有多项证据表明，大豆蛋白中的某些成分(S)参与了脂代谢的调节，参与脂代谢的激素之一是胰岛素。我们寻找能够影响胰岛素作用的大豆蛋白成分(S)。通过对分离的大鼠脂肪细胞进行纯化的多肽测序及其对脂肪分解的影响，证实了大豆球蛋白的A_1a和A_2酸性亚基在体外增强了胰岛素的作用。此外，这些蛋白质还显示出与胆汁酸结合的能力。因此，这些蛋白质可能是通过干扰类固醇吸附而发挥降胆固醇作用的候选蛋白质，这是大豆蛋白的一种众所周知的生理功能。而胆汁酸结合能力与胰岛素刺激活性无关。从豌豆种子中提取的豆蛋白酸性亚基具有这两种特性，表明这些特性可能是豆类蛋白所共有的。A_&lt；1a&gt；亚基(A_&lt；1a&gt；/tr)的胰酶产物也具有胰岛素刺激活性，并通过大鼠脂肪细胞对其分子机制进行了研究。A&lt；1a&gt；/tr不影响葡萄糖转运，而葡萄糖转运是胰岛素作用于细胞的主要过程。但是，A&lt；1a&gt；/tr提高了脂肪分解对胰岛素的反应性和敏感性。A&lt；1a&gt；/tr保护胰岛素不被降解，导致细胞内胰岛素浓度升高。在15ﾟC没有观察到胰岛素刺激活性，这表明胰岛素内化是蛋白质效应出现的必要条件，单靠抑制胰岛素降解不能解释对激素最大反应的增强效应。