| Popis: |
The specificity of cassava leaf β-glucosidase towards 33 glycosides was examined. Only 11 glycosides were hydrolysed. Among these, there was greater preference for p -nitrophenyl- p - d -glucoside, p -nitrophenyl-β- d -fucoside and linamarin than for o -nitrophenyl-β- d -glucoside, o -nitrophenyl-β- d -fucoside, p -nitrophenyl-β- d -galactoside, p -nitrophenyl-β- d -mannoside, p -nitrophenyl-β- d -xyloside, phenyl-β-glucoside, prunasin and salicin. Glycosides having disaccharide residues as well as α- and β-linked diglucosides were not hydrolysed. The type of glycone and aglycone for the glycoside appeared to be important for enzyme activity. Results of pH dependence studies using p -nitrophenyl-β- d -glucoside, p -nitrophenyl-β- d -fucoside and linamarin as substrates suggested involvement of an acidic amino acid side chain in the enzyme active site. Glucono-1,5-Iactone inhibited the enzyme competitively. The other monosaccharides and their derivatives tested did not show any inhibition of enzyme activity. |
