Stepaniak L, Gobbetti M, Sørhaug T, Fox P F, Højrup P
Department of Food Science, Agricultural University of Norway, As, Norway.
Z Lebensm Unters Forsch. 1996 Apr;202(4):329-33. doi: 10.1007/BF01206106.
Peptides inhibitory to the 70-kDa endopeptidase (PepO) from the cytoplasm of Lactococcus lactis ssp. lactis MG1363 were isolated from the supernatant (pH 4.6) of chymosin, tryptic and alpha-chymotryptic hydrolysates of beta-casein (beta-CN) by reversed-phase HPLC and identified by sequencing and mass spectrometry. Chymosin released beta-CN f193-209, kinetic constant (Ki) of which for inhibition of PepO was 60 microM. This peptide also inhibited (Ki = 1700 microM) the 95-kDa aminopeptidase (PepN) from L. lactis ssp. lactis MG 1363. Trypsin released two PepO-inhibitory peptides: one, beta-CN f69-97, was not degradable by PepO (Ki = 4.7 microM), while the other, beta-CN f141-163, was degradable by PepO but competitively inhibited hydrolysis of methionine enkephalin by PepO. A peptide, beta-CN f69-84, which inhibited PepO with a Ki of 8.1 microM, was isolated from the alpha-chymotryptic hydrolysate. Peptides released from beta-CN by trypsin or chymotrypsin had very little inhibitory activity against PepN. PepO degraded beta-CN f193-209 very slowly compared with the hydrolysis of methionine enkephalin. All four inhibitory peptides (beta-CN f193-209, f69-97, f69-84, f141-163) were readily degraded by thermolysin.
从乳酸乳球菌亚种乳酸乳球菌MG1363细胞质中分离出对70 kDa内肽酶（PepO）具有抑制作用的肽，这些肽是通过反相高效液相色谱法从β-酪蛋白（β-CN）的凝乳酶、胰蛋白酶和α-胰凝乳蛋白酶水解产物的上清液（pH 4.6）中分离得到的，并通过测序和质谱进行鉴定。凝乳酶释放出β-CN f193 - 209，其对PepO抑制作用的动力学常数（Ki）为60 μM。该肽还抑制（Ki = 1700 μM）来自乳酸乳球菌亚种乳酸乳球菌MG1363的95 kDa氨肽酶（PepN）。胰蛋白酶释放出两种抑制PepO的肽：一种是β-CN f69 - 97，不能被PepO降解（Ki = 4.7 μM），而另一种是β-CN f141 - 163，可被PepO降解，但能竞争性抑制PepO对甲硫氨酸脑啡肽的水解。从α-胰凝乳蛋白酶水解产物中分离出一种抑制PepO的肽β-CN f69 - 84，其Ki为8.1 μM。胰蛋白酶或胰凝乳蛋白酶从β-CN释放的肽对PepN的抑制活性很小。与甲硫氨酸脑啡肽的水解相比，PepO对β-CN f193 - 209的降解非常缓慢。所有四种抑制性肽（β-CN f193 - 209、f69 - 97、f69 - 84、f141 - 163）都很容易被嗜热菌蛋白酶降解。
