棘孢曲霉SM-L22β-葡萄糖苷酶的纯化与性质

PURIFICATION AND PROPERTIES OFβ-GLUCOSIDASE FROM ASPERGILLUS ACULEATUS SM-L22

通过分子筛层析和离子交换层析等手段,分离纯化了棘孢曲霉SM-L22纤维素酶系中的β-葡萄糖苷酶组分.通过SDS-PAGE和IEF电泳测得其分子量为57.9 kDa,等电点为pH 4.5.该酶组分的最适温度60℃,最适pH 5.5,在40℃以下以及pH 3.0~10.0范围内稳定.Fe2+和Mn2+ 对酶有激活作用,而 EDTA对酶有较明显的抑制作用.底物专一性实验表明,该酶可作用于纤维二糖、水杨素和乳糖.作用于纤维二糖和水杨素的Km值分别为17.13 ( 10-3 mol/L 和11.93 ( 10-3 mol/L,Vmax分别为3.456 ( 10-4 mol/L/min和7.139 ( 10-4 mol/L/min,Kcat分别为3.75 S-1和7.73 S-1.

A β-glucosidase component from Aspergillus aculeatus SM-L22 was seperated and purified by exclution chromatography and ion-exchange chromatography. By SDS-PAGE and IEF, the molecular weight of the enzyme was determined as 57.9 kD and the isoelectric point was pH 4.5. The enzyme showed optimal activity at pH 5.0 and 60℃. It was stable in pH 3.0~10.0 and under 40℃. The result showed that the enzyme can only act low molecular β-glucosidic compounds such as cellobiose, Salicin and lactose. The Km, Vm and Kcat was 17.13 10-3 mol/L, 3.456 10-4 mol/L/min and 3.75 S-1 when cellobiose was as substrate, and the parameters were 11.93 10-3 mol/L, 7.139 10-4 mol/L/min and 7.73 S-1 respectively, when D-(-)-Salicin as substrate. Fe2+, Mn2+ can activate the enzymatic activity and EDTA inhibite it.