PROPERTIES OF ?-GALACTOSIDASE FROM BACILLUS STEAROTHERMOPHILUS
- VernacularTitle:嗜热脂肪芽孢杆菌?-半乳糖苷酶的性质
- Author:
Dongzhi WEI
;
Shaoxin CHEN
;
Xiaolan WANG
;
Qinsheng YUAN
;
Jun YU
;
- Publication Type:Journal Article
- Keywords:
Bacillus stearothermophilus, Thermostable ?-galactosidase,Galacto-oligosaccharides
- From:
Microbiology
1992;0(01):-
- CountryChina
- Language:Chinese
-
Abstract:
A themostable intracellular ? galactosidase from a thermophilic Bacillus stearothermophilus was purified by a combination of (NH 4) 2SO 4 fractionation,ion exchange (DEAE 22)and gel filtration (Sephades G 75).The optimum temperature and pH of the enzyme acivity were 60℃and pH6.4 respectively.The ? galatosidase activity exhibited thermosttability at 50 ℃.The enzyme was significaantly activated by alkali and alkali earth metal ions.The activity was inhibited by Zn 2+ 、 Fe 3+ 、 Cu 2+ Reducing agents enhanced ? galactosidase activity.Thiol binding agents drastically decreased the enzyme activity.The enzyme was specific for ? D glycosidic linkages,and the identity of the aglycone moiety also influenced enzyme activity.At 55℃the Km for O nitrophenyl ? D galactosidase(ONPG)and lactose were 2.63mmol/L and 4.39mmol/L, respectively,and Vmax for both substrates were 1.93?10 5 mmol.min 1 .mg 1 protein6.54?10 5 mmol.min 1 .mg 1 protein,respectively.The enzyme was inhibited by glucose (the products of lactose hydrolysis,ki 2.47mmol/L),but not by galactose.In addition,the enzyme possessed transgalactosylation activity.Galacto oligosaccharides,both tri and tetrasaccharide,were involved in the products during lactose hydrolysis.
