Okayama Prefectural Technology Center for Agriculture, Forestry, and Fisheries, Research Institute for Biological Sciences (RIBS), Okayama, 7549-1 Kibichuo-cho, Kaga-gun, Okayama 716-1241, Japan.
Food Chem. 2012 Sep 15;134(2):797-802. doi: 10.1016/j.foodchem.2012.02.183. Epub 2012 Mar 7.
The insulinotropic hormone glucagon-like peptide-1 is metabolised extremely rapidly by the ubiquitous enzyme dipeptidyl peptidase IV (DPP-IV). Therefore, human DPP-IV is a key regulator involved in the prevention and treatment of type 2 diabetes. To simplify the method of producing an inhibitory peptide against DPP-IV, we focused on rice bran (RB) as a source and subjected proteins from defatted RB to enzymatic proteolysis using 2 commercial enzymes. The RB peptides produced with Umamizyme G exhibited 10 times the inhibitory activity as those produced with Bioprase SP. The half-maximal inhibitory concentration (IC(50)) value of the RB peptides was 2.3 ± 0.1mg/ml. Leu-Pro and Ile-Pro were identified as the inhibitory peptides among the RB peptides produced with Umamizyme G. Ile-Pro was the strongest DPP-IV inhibitor among the 15 Xaa-Pro dipeptides and Pro-Ile tested. Ile-Pro competitively inhibited DPP-IV (K(i)=0.11 mM). Mass spectrometry indicated that the contents of Leu-Pro and Ile-Pro in the RB peptides were 2.91 ± 0.52 μg/mg.
胰高血糖素样肽-1 是一种促胰岛素激素，可被广泛存在的二肽基肽酶 IV（DPP-IV）迅速代谢。因此，人类 DPP-IV 是预防和治疗 2 型糖尿病的关键调节剂。为了简化针对 DPP-IV 的抑制肽的生产方法，我们将米糠（RB）作为来源，并使用 2 种商业酶对脱脂 RB 中的蛋白质进行酶解。用 Umamizyme G 生产的 RB 肽的抑制活性是用 Bioprase SP 生产的 RB 肽的 10 倍。RB 肽的半最大抑制浓度（IC（50））值为 2.3±0.1mg/ml。在用 Umamizyme G 生产的 RB 肽中，鉴定出亮氨酸-脯氨酸（Leu-Pro）和异亮氨酸-脯氨酸（Ile-Pro）为抑制肽。Ile-Pro 是在测试的 15 种 Xaa-Pro 二肽和 Pro-Ile 中最强的 DPP-IV 抑制剂。Ile-Pro 竞争性抑制 DPP-IV（K(i)=0.11 mM）。质谱分析表明，RB 肽中 Leu-Pro 和 Ile-Pro 的含量分别为 2.91±0.52μg/mg。
