低聚果糖合成酶──果糖转移酶的部分酶学性质研究

Some Properties of Fructosyltransferase from Asp.niger AS0023

研究从土壤中筛选得到的黑曲霉ＡＳ００２３菌株所产的β－果糖转移酶的一些酶学性质。该酶的最适ｐＨ为５．０，最适温度为５０℃，有较好的热稳定性和较宽的ｐＨ（３．５～１０）适宜范围；并研究了１２种化学物质对酶活的影响和底物的特异性。结果显示，钴离子对该酶有一定的激活作用；底物分子越大其反应速度越慢。该酶的米氏常数Ｋ＿ｍ＝４７ｍｍｏｌ，葡萄糖是酶反应的竞争性抑制剂，其Ｋ＿ｉ＝３３０ｍｍｏｌ．当５０％（Ｗ／ｖ）蔗糖与酶在ｐＨ５．０和５０℃作用１６ｈ时，得到５２％（产物／总糖）低聚果糖。

An Aspergillus niger strain AS0023 producing fructosyltransferase(FTS)was selected from soil.The optimum pH and temperature for producing FTS were 5.0 and 50℃, respectively.The advantage of the enzyme were high activity over wide range of pHfrom 3.5 to 10 and good thermostability.The effect of 12 chemical substances on FTSwere tested,among which cobalt ion had a positive effect on the activity of FTS.The K_mvalue of the enzyme on sucrose was 47mmol.Glucose was a competive inhibiter and the K_ivalue was 330mmol.52% FOS (FOS/total sugar)was produced after 50%sucrose solution was incubated with the enzyme at 50℃,pH5.0 for 16 hours.