초록
An exoinulinase gene from Aspergillus ficuum JNSP5-06 was overexpressed in Escherichia coli. Two exons of the exoinulinase gene were amplified separately, joined together by an overlap PCR, and expressed in E. coli. The molecular weight of the recombinant exoinulinase was estimated to be 63kDa. The K<SUB>m</SUB> and V<SUB>max</SUB> values for inulin were (7.1+/-0.2)mM and (1000.0+/-0.1)μmol/(minmgprotein), respectively. The K<SUB>m</SUB> and V<SUB>max</SUB> values for sucrose were (347.6+/-25.9)mM and (12,037.0+/-801.9)μmol/(minmgprotein), respectively. The optimum temperature and pH with inulin as the substrate were 60<SUP>o</SUP>C and 4.0, respectively. The optimum temperature and pH with sucrose as the substrate were 55<SUP>o</SUP>C and 5.0, respectively. Its activity was increased by Mn<SUP>2+</SUP>, completely inhibited by Cu<SUP>2+</SUP>, and strongly inhibited by Al<SUP>3+</SUP>, Ag<SUP>+</SUP>, Fe<SUP>3+</SUP>, Fe<SUP>2+</SUP>, Ni<SUP>2+</SUP>, Zn<SUP>2+</SUP>, and Mg<SUP>2+</SUP>. The product of hydrolysis of inulin by the recombinant exoinulinase was fructose.