蛋白质的消化吸收及其功能评述

Bioactive Peptides:Absorption,Utilization and Functionality

蛋白质及其肽类食品,不仅是人体重要的营养物质,而且具有重要的健康功能。大量研究表明,单独食用蛋白质或氨基酸,尽管其氨基酸组成是均衡的,也不如食用酶解肽,这说明蛋白质经过酶解不仅可以为机体提供氨基酸营养,还可以产生多种功能肽,对机体健康发挥重要功能。但是,机体是一个自我调节、自我更新和自稳定系统,它的免疫防御系统不允许异己分子的生物大分子进入机体,特别是蛋白质或多肽,因为它们有可能是入侵者。即使少量蛋白分子可以偶尔进入体内,那主要是因为机体需要从肠道中采集样品,以便认识周围的物质世界,从而针对它们提前构成其获得性免疫防御系统。进入体内的蛋白质或多肽并不是为了让他们发挥功能,而是很快被处理和酶解,由抗原提呈细胞将其抗原决定簇提交给T细胞,由微皱褶(M)细胞负责将完整蛋白传递给B细胞作为抗原表位,激活B细胞,从而构成机体的获得性免疫的基础。本文经过对相关研究成果的综合分析认为:酶解肽主要是通过和胃肠系统中的微生物和受体相互作用发挥其生物功能。另外,和氨基酸相比,短肽,特别是二、三肽更容易被其运载体(PepT1)吸收,而且效率更高,更有利于机体中不同组织和器官的利用,从而构成氨基酸营养吸收和利用的基础,同时对机体营养和吸收控制发挥重要的调节作用。通过对蛋白质的消化和吸收及其功能的评述试图为肽类功能性食品开发提供理论依据和参考。

Dietary proteins and their enzymolytic products exert a wide range of nutritional,functional and biological activities for human health.A large number of data showed that protein hydrolytic products are absorbed and transited more effectively than intact protein or free amino acids alone,supporting the notion that digestion is important for its uptake and circulation even if the amino acid compositions are exactly balanced.Furthermore,when the protein was administered orally as a hydrolysate instead of in an intact form or free amino acid,the healthy functions can be observed,suggesting that bioactive peptides can be liberated by proteolytic enzymes.However,the body is a self-regulatory,self-renew,and selfstabilization system,so the immune defense system never allows any dissident biomacromolecules,especially diet proteins and peptides to be taken in,for that maybe some invaders.Even if a small amount of intact proteins are occasionally taken up,which is due to the molecule structure recognition of substances around by sampling from intestinal tract.The major functions are to establish as the adaptive immunity defense system for specific antigens.After absorbed,these peptides will be rapidly hydrolyzed and processed by antigen presenting cells（APC） to present the antigenic determinants to Th cells.The membranous microfold（M） cells can bring intact protein to B cells as antigen epitopes for antibody class switching and secreting.Base on these investigations,diet proteins and corresponding enzymolytic peptides mainly offer their functions by the interaction with gastrointestinal mucosal systems and intestinal microorganisms.On the other hand,the accumulated data have demonstrated that transport of di-and tripeptides is a faster and effective route of uptake per unit of time than their free AA or intact protein by intestinal peptide transporter,PepT1.Furthermore,the di-and tripeptides are more efficiently than free AA or intact protein with the same respective AA compositions,and these peptides may be transported by circulation to different tissues or organs and used for different purpose more efficiently.This review will also provide a theoretical basis for the research and exploitation of bioactive peptides for special foods.