水解酶反应中酶肽链氨基酸的脱落  

Shedding of amino acids from enzyme peptide chain in hydrolase reaction

作　　者：赵信池 王金辉[1] 李瑞龙[1] 刘起睿 赵长新[1] ZHAO Xin-chi;WANG Jin-hui;LI Rui-long;LIU Qi-rui;ZHAO Chang-xin(School of Bioengineering,Dalian Polytechnic University,Dalian 116033)

机构地区：[1]大连工业大学生物工程学院,大连116033

出　　处：《中国食品添加剂》2020年第10期20-25,共6页China Food Additives

摘　　要：通过对α-淀粉酶、蔗糖酶、糖化酶等的酶促反应研究发现,酶分子在经过多次酶促反应后,活力会下降。为了研究不同种类的酶在酶促反应中的现象,酶促反应中氨基酸脱落的原因以及影响脱落的因素,采用α-淀粉酶为样本;底物浓度及反应时间作为实验条件;通过茚三酮显色反应和分光光度计检测样品中氨基酸的浓度;采用氨基酸色谱分析仪对其水解反应产物进行分析。通过对α-淀粉酶、蔗糖酶、糖化酶等的酶促反应研究发现,在酶促反应中,酶分子肽链上的氨基酸均会发生脱落现象,种类可达数十种,从增长速率来看,苏氨酸的增长倍数为5.375,其次为赖氨酸3.428和丝氨酸1.972,其余氨基酸增长幅度均在1.1~1.5之间;从比重来看,苏氨酸、丝氨酸和谷氨酸在新增的氨基酸中最高达40%,比重随反应逐渐减小,但仍在10%以上,而其余氨基酸均低于10%,且增长缓慢,说明苏氨酸、丝氨酸、谷氨酸脱落较早且量大。此外,在一定的底物浓度范围内氨基酸的脱落量与底物浓度呈正相关。即实验中酶催化反应底物浓度越高,反应时间越长,脱落的氨基酸越多。在酶促反应中,氨基酸脱落的现象存在普适性。根据酶的诱导契合学说,酶催化反应发生的氨基酸脱落现象应当与酶变构密切相关,酶的变构应该是酶分子氨基酸脱落的主要原因。而酶肽链上氨基酸脱落意味着氨基酸结构被逐渐破坏,以致酶变构难以进行,直至失去活性。Through the researches on enzymatic reactions ofα-amylase,sucrose and glucoamylase enzyme,it is found that the activity of enzyme molecules can be reduced after enzyme molecules are subjected to the multiple enzymatic reactions.The research aims at researching the phenomenon of different types of enzymes in the enzymatic reactions,the reason for amino acid shedding in the enzymatic reactions and factors affecting the shedding.Theα-amylase was selected as sample,and substrate concentration and reaction time are taken as experimental conditions;the concentration of the amino acid was detected in the sample through a ninhydrin chromogenic reaction and a spectrophotometer;and catalytic reaction products of reaction were analyzed by adopting an amino acid analyzer.In enzymatic reactions,the shedding phenomenon occurs on the amino acids on an enzyme molecular peptide chain through the researches on the enzymatic reactions onα-amylase,sucrase and glucoamylase.More than ten kinds of shed amino acids were detected,from the perspective of growth rate,the growth factor of threonine was 5.375,followed by lysine 3.428 and serine 1.972.The average growth rate of the remaining amino acids was between 1.1~1.5;threonine,serine and glutamic acid are among the supplemented amino acids up to 40%,the proportion gradually increased with the reaction,but it was still above 10%,while the remaining amino acids were all lower than 10%,and the growth was slow,indicating that threonine,serine,and glutamic acid were replaced earlier and in large amounts.In addition,in a certain substrate concentration range,the shedding amount of the amino acid was in positive correlation with the substrate concentration,namely,the higher the concentration of an enzyme catalytic reaction substrate in an experiment is,the longer the reaction time is,and the more amino acids shed.In the enzymatic reactions,there is universality for the phenomenon of the amino acid shedding.According to the induced fit theory of the enzyme,the amino acid shedding phenomenon

关 键 词：酶促反应 氨基酸脱落 茚三酮比色法 诱导契合学说 

分 类 号：O629.8/Q556[理学—有机化学]