Davies P H, Messer M
Biol Neonate. 1984;45(4):197-202. doi: 10.1159/000242004.
Cathepsin B and D activities were assayed in homogenates of the mucosa of the proximal, middle, and distal sections of the small intestine of suckling rats of various ages and of adult rats. Cathepsin B activity was determined using N-benzoyl-L-phenylalanyl-L-valyl-L-arginine-p-nitroanilide as substrate in the presence of trypsin inhibitor (pH optimum: 5.0-5.5). Cathepsin D activity was determined by measuring the pepstatin A sensitive action on denatured haemoglobin (pH optimum: 3.0-3.5). In the distal intestine, the activities of both cathepsins increased 6- to 10-fold during the first 2 weeks post partum and then sharply declined to the low values seen in adult rats, but in the proximal intestine the activities were low throughout the suckling period. In vitro digestion of casein by ileal mucosa of 8-day-old rats was almost completely inhibited by the combined actions of leupeptin and pepstatin A. The results show that cathepsin B- and D-like proteinases could play an important role in the digestion of milk proteins by suckling rats.
在不同年龄的乳鼠及成年大鼠小肠近端、中段和远端黏膜匀浆中测定了组织蛋白酶B和D的活性。组织蛋白酶B活性测定采用N-苯甲酰-L-苯丙氨酰-L-缬氨酰-L-精氨酸对硝基苯胺为底物，并在存在胰蛋白酶抑制剂的情况下进行（最适pH：5.0 - 5.5）。组织蛋白酶D活性通过测量对变性血红蛋白的胃蛋白酶抑制剂A敏感作用来测定（最适pH：3.0 - 3.5）。在远端小肠，两种组织蛋白酶的活性在产后前2周增加了6至10倍，然后急剧下降至成年大鼠所见的低值，但在近端小肠，整个哺乳期活性都很低。8日龄大鼠回肠黏膜对酪蛋白的体外消化几乎完全被亮抑酶肽和胃蛋白酶抑制剂A的联合作用所抑制。结果表明组织蛋白酶B样和D样蛋白酶可能在乳鼠消化乳蛋白中起重要作用。
