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Abstract：
A β-glucosidase from Penicillium italicum was purified with a specific activity of 61.8 U/mg, using a chromatography system. The native form of the enzyme was an 88.5-kDa tetramer with a molecular mass of 354 kDa. Optimum activity was observed at pH 4.5 and 60℃, and the half-lives were 1,737, 330, 34, and 1 hr at 50, 55, 60, and 65℃, respectively. Its activity was inhibited by 47% by 5 mM Ni(2+). The enzyme exhibited hydrolytic activity for p-nitrophenyl-β-D-glucopyranoside (pNP-Glu), p-nitrophenyl-β-D-cellobioside, p-nitrophenyl-β-D-xyloside, and cellobiose, however, no activity was observed for p-nitrophenyl-β-D-lactopyranoside, p-nitrophenyl-β-D-galactopyranoside, carboxymetyl cellulose, xylan, and cellulose, indicating that the enzyme was a β-glucosidase. The k(cat)/K(m) (s(-1) mM(-1)) values for pNP-Glu and cellobiose were 15,770.4 mM and 6,361.4 mM, respectively. These values were the highest reported for β-glucosidases. Non-competitive inhibition of the enzyme by both glucose (K(i) = 8.9 mM) and glucono-δ-lactone (K(i) = 11.3 mM) was observed when pNP-Glu was used as the substrate. This is the first report of non-competitive inhibition of β-glucosidase by glucose and glucono-δ-lactone.
摘要：
从意大利青霉中纯化出一种β-葡萄糖苷酶，比活性为61.8U/mg，使用色谱系统。酶的天然形式是分子量为354kDa的88.5kDa四聚体。在pH4.5和60℃下观察到最佳活性，在50、55、60和65℃下的半衰期分别为1,737、330、34和1小时，分别。5mMNi（2）抑制了47％的活性。该酶对对硝基苯基-β-D-吡喃葡萄糖苷（pNP-Glu）具有水解活性，对硝基苯基-β-D-纤维二糖苷，对硝基苯基-β-D-木糖苷,和纤维二糖，然而,未观察到对硝基苯基-β-D-吡喃乳糖苷的活性，对硝基苯基-β-D-吡喃半乳糖苷，羧甲基纤维素，木聚糖,和纤维素，表明该酶是β-葡萄糖苷酶。pNP-Glu和纤维二糖的k(cat)/K(m)(s(-1)mM(-1))值分别为15,770.4mM和6,361.4mM,分别。这些值是β-葡糖苷酶报告的最高值。当使用pNP-Glu作为底物时，观察到葡萄糖（K（i）=8.9mM）和葡糖酸-δ-内酯（K（i）=11.3mM）对酶的非竞争性抑制。这是葡萄糖和葡糖酸-δ-内酯对β-葡糖苷酶的非竞争性抑制的首次报道。
