Yan TR, Lin YH, Lin CL
Laboratory of Biochemistry, Department of Bioengineering, Tatung Institute of Technology, 40 Chung-Shang North Road 3rd Sec., Taipei, Taiwan 10451, Republic of China.
J Agric Food Chem. 1998 Feb 16;46(2):431-437. doi: 10.1021/jf9702499.
An extracellular beta-glucosidase II (beta-Glu II) has been purified to homogeneity by column chromatography from Aspergillus niger CCRC 31494. Its molecular mass was estimated to be 360 kDa by gel filtration and 120 kDa by SDS-PAGE. The enzyme has a pI of 4.0 and has optimum activity at pH 4.5 and 60 degrees C. The beta-Glu II was completely inhibited by 5.0 mM Fe(2+). Methanol (20%, v/v) activated the enzyme activity at 1.8-fold. V(max) values of 10.2 and 464 units/mg were found for p-nitrophenyl beta-D-glucoside (K(m) = 2.2 mM) and for cellobiose (K(m) = 15.4 mM). The enzyme was strongly inhibited by substrates, p-nitrophenyl beta-D-glucopyranoside in excess of 7.5 mM and cellobiose in excess of 50 mM, and was competitively inhibited by glucose with a K(i) of 5.7 mM. Transglucosylation products of cellotriose, methyl beta-glucoside and ethyl beta-glucoside, were obtained under neutral conditions and in the presence of methanol and ethanol, respectively.
已通过柱色谱法从黑曲霉CCRC 31494中纯化出一种细胞外β-葡萄糖苷酶II（β-Glu II），使其达到同质。通过凝胶过滤法估计其分子量为360 kDa，通过SDS-PAGE法估计为120 kDa。该酶的pI为4.0，在pH 4.5和60℃时具有最佳活性。5.0 mM的Fe(2+)可完全抑制β-Glu II。甲醇（20%，v/v）可使酶活性提高1.8倍。对硝基苯基β-D-葡萄糖苷（K(m)=2.2 mM）和纤维二糖（K(m)=15.4 mM）的V(max)值分别为10.2和464单位/毫克。该酶受到底物的强烈抑制，超过7.5 mM的对硝基苯基β-D-吡喃葡萄糖苷和超过50 mM的纤维二糖会抑制该酶，葡萄糖对其具有竞争性抑制作用，K(i)为5.7 mM。分别在中性条件下以及在甲醇和乙醇存在的情况下，获得了纤维三糖、甲基β-葡萄糖苷和乙基β-葡萄糖苷的转糖基化产物。
