小麦麸皮内源性β-木糖苷酶的酶学特性

Enzymatic characteristics of endogenous β-xylosidase in wheat bran

以硝基苯酚-木糖苷为底物，在底物浓度为1 mg／ml ，提取液pH值为5的条件下，测定了小麦麸皮内源性β-木糖苷酶的酶活力，并对4种小麦麸皮内源性β-木糖苷酶的酶学特性进行了比较。结果表明：不同品种小麦麸皮内源性β-木糖苷酶的酶活力不同，同种小麦的粗麸皮和细麸皮中的内源性β-木糖苷酶的酶活力也不同；细麸皮中β-木糖苷酶的酶活力均高于粗麸皮中β-木糖苷酶酶活力，粗麸皮中郑麦8998的β-木糖苷酶酶活力最大，细麸皮中花培8号小麦β-木糖苷酶酶活力最大；郑麦8998、花培8号、郑麦366、郑麦90234种小麦粗麸皮内源性β-木糖苷酶的最适反应温度分别为60、50、50和60℃；最适反应pH值均为5；花培8号和郑麦366两种小麦粗麸皮内源性β-木糖苷酶在20～50℃范围内，酶活力稳定性较好，而郑麦8998和郑麦9023两种小麦粗麸皮内源性β-木糖苷酶在20～60℃范围内，温度对β-木糖苷酶的酶活力影响较小；4种小麦粗麸皮内源性β-木糖苷酶在pH值为5～6时，酶活力稳定性较好；Ca2＋、Co2＋促进β-木糖苷酶的酶活力，而Ag＋对β-木糖苷酶的酶活力有较强的抑制作用。

Enzyme activities of the endogenousβ-xylosidase in wheat bran were investigated in the experiment under the followingconditions：PNP-β-Xylopyranoside （PNPX）were used as the substrate with 1 mg/ml of substrate concentration and 5for pH value of the extracts.Enzymatic characteristics of endogenousβ-xylosidase in 4 types of wheat bran were compared.Results showed that：enzyme activities varied from different varieties of wheat bran;Differences were also found in the enzymeactivity for both coarse and fine wheat bran in the same kind;the enzyme activity in fine bran was observed higher than those incoarse bran.The maximum enzyme activity ofβ-xylosidase was found both in the coarse bran of wheat variety-zhengmai 8998and the fine bran of wheat variety-huapei 8;60℃,50℃,50℃and 60℃was the optimum reaction temperature of theendogenousβ-xylosidase for wheat varieties zhengmai 8998,huapei 8,zhengmai 366 and 9023 respectively;pH 5 was also oneof the optimal reaction conditions for the 4 varieties;For coarse bran in wheat huapei 8 and zhengmai 366,a better enzymeactivity of endogenousβ-xylosidase was got within 20~50℃,while 20~60℃was for coarse bran of wheat zhengmai 8998 and9023;Impact of temperature was not significant in the enzyme activity of endogenousβ-xylosidase;Moreover,a better enzymestability was achieved for all the 4 wheat varieties when the pH value was in the range of 5~6.Ca2＋,Co2＋were proved to promotethe enzyme activity,while Ag＋led an inhibiting role in this regard.