Eriksen Ellen K, Holm Halvor, Jensen Einar, Aaboe Ragnhild, Devold Tove G, Jacobsen Morten, Vegarud Gerd E
Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, As, Norway.
Br J Nutr. 2010 Aug;104(3):374-81. doi: 10.1017/S0007114510000577. Epub 2010 Mar 22.
The objective of the present study was twofold: first to compare the degradation patterns of caprine whey proteins digested with either human digestive juices (gastric or duodenal) or commercial porcine enzymes (pepsin or pancreatic enzymes) and second to observe the effect of gastric pH on digestion. An in vitro two-step assay was performed at 37 degrees C to simulate digestion in the stomach (pH 2, 4 or 6) and the duodenum (pH 8). The whey proteins were degraded more efficiently by porcine pepsin than by human gastric juice at all pH values. Irrespective of the enzyme source, gastric digestion at pH 2 followed by duodenal digestion resulted in the most efficient degradation. Lactoferrin, serum albumin and the Ig heavy chains were highly degraded with less than 6 % remaining after digestion. About 15, 56 and 50 % Ig light chains, beta-lactoglobulin (beta-LG) and alpha-lactalbumin remained intact, respectively, when digested with porcine enzymes compared with 25, 74 and 81 % with human digestive juices. For comparison, purified bovine beta-LG was digested and the peptide profiles obtained were compared with those of the caprine beta-LG in the digested whey. The bovine beta-LG seemed to be more extensively cleaved than the caprine beta-LG in the whey. Commercial enzymes appear to digest whey proteins more efficiently compared with human digestive juices when used at similar enzyme activities. This could lead to conflicting results when comparing human in vivo protein digestion with digestion using purified enzymes of non-human species. Consequently the use of human digestive juices might be preferred.
一是比较用人类消化液（胃液或十二指肠液）或商业猪酶（胃蛋白酶或胰酶）消化的山羊乳清蛋白的降解模式，二是观察胃pH值对消化的影响。在37℃下进行体外两步试验，以模拟胃（pH 2、4或6）和十二指肠（pH 8）中的消化过程。在所有pH值下，猪胃蛋白酶比人类胃液更有效地降解乳清蛋白。无论酶源如何，pH 2时的胃消化随后进行十二指肠消化导致最有效的降解。乳铁蛋白、血清白蛋白和免疫球蛋白重链高度降解，消化后剩余不到6%。与用人类消化液消化时分别有25%、74%和81%剩余相比，用猪酶消化时，约15%、56%和50%的免疫球蛋白轻链、β-乳球蛋白（β-LG）和α-乳白蛋白保持完整。为作比较，对纯化的牛β-LG进行消化，并将获得的肽谱与消化乳清中的山羊β-LG的肽谱进行比较。牛β-LG似乎比乳清中的山羊β-LG被更广泛地切割。当以相似的酶活性使用时，商业酶似乎比人类消化液更有效地消化乳清蛋白。在比较人类体内蛋白质消化与使用非人类物种的纯化酶进行的消化时，这可能导致相互矛盾的结果。因此，可能更倾向于使用人类消化液。
