消化
词汇介绍
拓展阅读
解析
pepsin 英 [ˈpepsɪn] 美 ['pepsɪn]
释义 n. 胃蛋白酶
例句 Ulcer is caused by the bacteria called Helicobacter pylori and by excessive internal secretions of gastric acid and pepsin. 溃疡是由细菌引起的称为幽门螺杆菌与胃酸分泌过多、胃蛋白酶的内部。
概述
概述
胃蛋白酶（pepsin,Pep）属于天冬氨酸蛋白水解酶类，是胃消化蛋白水解酶，相对分子质量为 3.1×104～3.6×104，其前体是胃蛋白酶原，由胃黏膜主细胞所分泌，功能是将食物中的蛋白质分解为小的肽片段。主细胞分泌的是胃蛋白酶原，胃蛋白酶原经胃酸或者胃蛋白酶刺激后，形成胃蛋白酶。胃蛋白酶是胃内唯一的一种蛋白水解酶，其最适pH值为1～2。胃蛋白酶作用的主要部位是芳香族氨基酸，或酸性氨基酸的氨基所组成的肽链，具有消化蛋白质的能力。
正常值
基础胃液胃蛋白酶分泌量为84.4±9.72mg酪氨酸/h；最高胃蛋白酶分泌量为190.29±15.31酪氨酸/h（Anson氏法）；420±208kU/L（改良李氏法）。
性状
本品为白色或淡黄色的粉末；无霉败臭；有引湿性；水溶液显酸性反应。
临床意义
胃液胃蛋白酶测定可用于鉴别神经性低酸症和胃性低酸症，当胃酸过少或胃蛋白酶缺乏时，前者胃蛋白酶的含量有时正常而后者盐酸与胃蛋白酶同时缺乏。慢性胃炎、慢性胃扩张、慢性十二脂肠炎等胃蛋白酶的分泌常减少。一般胃酸基础分泌高的疾患，如十二指肠溃疡等，胃蛋白酶活性增高。
作用方法
胃蛋白酶应保存在低温环境中（-20℃至-80℃），以防止其发生自降解。储存于pH值大于11的溶液中或对其进行还原性甲基化也可以有效防止自降解的发生；当pH值回到6时，胃蛋白酶的活性即可恢复。其消化力以含0.2%～0.4%盐酸（pH=1.6～1.8）时为最强，故常与稀盐酸合用。
主要用途
（1）药用的胃蛋白酶可以用于治疗消化不良；
（2）用于因食蛋白性食物过多所致消化不良、病后恢复期消化功能减退以致慢性萎缩性胃炎、胃癌、恶性贫血而导致的胃蛋白酶缺乏。
用法用量
饭后或饭前口服0.2-0.4克，每日3次，同时服稀盐酸0.5-2毫升。
注意事项
不能与抗酸剂或硫糖铝使用，以免降效。
复制标题富含多酚的苹果基质在体外胃消化中受pH和胃蛋白酶调节的脂质保护
发表时间：2019-07-17
影响指数：3.2
作者： Gaëtan Boléa
期刊：Food & Function
Lipid oxidation takes place in the gastric tract after the ingestion of a Western diet rich in ω-6 polyunsaturated fatty acids (PUFA) and red meat (heme iron). The incorporation of oxidation products such as 4-hydroxy-2-nonenal (4-HNE) into low-density lipoproteins is further correlated to endothelial dysfunction. Gastric postprandial stress could thus be reduced by antioxidant phytomicronutrients. The aim of this study was to investigate dietary lipid oxidation and its inhibition by apple polyphenols under different matrix forms (fresh fruit, puree, extract) under in vitro gastric digestion conditions. A deep insight was given into the two factors pH and pepsin governing the metmyoglobin-initiated lipid oxidation of sunflower oil-in-water emulsions simulating the physical state of dietary lipids. Our results first showed that pepsin accelerated lipid oxidation at pH 5 through the formation of a micro-metmyoglobin form likely displaying a higher accessibility to lipids. Spectroscopic studies further highlighted the formation of a reversible unfolded metmyoglobin form at pH 3 which was shown to be more pro-oxidant in the absence of pepsin. At nutritional levels, the three apple matrices inhibited less efficiently the accumulation of lipid-derived conjugated dienes and 4-HNE at pH 5 when pepsin was present whereas at pH 3 the opposite was true. High initial bioaccessibilities of monomeric phenolic compounds were evidenced for both puree (57–74%) and the phenolic extract (79–96%) compared to fresh apple (1–14%) supporting their greater antioxidant capacity. By contrast, the bioaccessibility of dimer B2 was low for all matrices suggesting non-covalent binding to apple pectins.
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