Identification of a covalent .alpha.-D-glucopyranosyl enzyme intermediate formed on a .beta.-glucosidase

1988 ◽  
Vol 110 (25) ◽  
pp. 8551-8553 ◽  
Author(s):  
Stephen G. Withers ◽  
Ian P. Street
Keyword(s):  
Beta Glucosidase ◽  
Enzyme Intermediate

scholarly journals The mechanism of action of β-glucosidase from Botryodiplodia theobromae Pat

1987 ◽  
Vol 241 (2) ◽  
pp. 455-462 ◽  
Author(s):  
G M Umezurike
Keyword(s):  
Mechanism Of Action ◽  
Rate Equation ◽  
Enzymic Activity ◽  
Botryodiplodia Theobromae ◽  
Acidic Group ◽  
Linear Decrease ◽  
Low Concentrations ◽  
Acetic Acid Buffer ◽  
Beta Glucosidase ◽  
Enzyme Intermediate

The activity of the high-molecular-weight beta-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21) obtained from culture filtrates of Botryodiplodia theobromae Pat. was affected by added NaCl in such a way that an initial phase of stimulation was followed by a phase of rapid non-linear decrease in velocity and finally by a phase of slow linear decrease in velocity as the concentration of NaCl was increased. In the presence of 0.014 M-sodium acetate/acetic acid buffer (pH 5.0) there was a slight increase in enzymic activity in the presence of low concentrations of dioxan (up to about 10% dioxan) and a rapid decrease in enzymic activity at higher dioxan concentrations, but both effects were mitigated in the presence of 0.1 M buffer. The order of efficiency of added glucosyl acceptors in beta-glucosidase-catalysed reactions was found to be fructose greater than sucrose greater than glycerol greater than methanol. The enzyme was inactivated by the active-site-directed compound conduritol-B-epoxide; but this inactivation was concentration-dependent, was prevented by 10 mM-glucose, and involved an acidic group with pKa 4.3. A rate equation has been derived on the assumption of a mechanism of action involving a solvent-separated and an intimate glucosyl cation-carboxylate ion-pair intermediate and an alpha-glucosyl enzyme intermediate [Umezurike, G. M. (1981) Biochem. J. 199, 203-209]. Calculations based on the application of the derived rate equation and the calculated kinetic parameters show that the rate equation explains the peculiar properties of beta-glucosidase in the presence of added glucosyl acceptors or of NaCl.

beta-Glucosidase activities and HCN liberation in unimbibed and imbibed seeds, and the induction of cocklebur seed germination by cyanogenic glycosides

1991 ◽  
Vol 83 (1) ◽  
pp. 34-40 ◽  
Author(s):  
Yohji Esashi ◽  
Shinichi Matsuyama ◽  
Hiroki Ashino ◽  
Maria Ogasawara ◽  
Ryo Hasegawa
Keyword(s):  
Seed Germination ◽  
Cyanogenic Glycosides ◽  
Beta Glucosidase
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