Kinetics and equilibria of condensation reactions between monosaccharide pairs catalyzed by Aspergillus niger glucoamylase

Abstract

Arabinose, fructose, galactose, myo-inositol, lyxose, mannose, ribose, and xylose were incubated individually and with glucose in the presence of Aspergillus niger glucoamylase at pH 4.5 and 45°C. Glucoamylase condenses galactose, glucose, and mannose individually into disaccharides. It also produces mixed disaccharides when each of the eight carbohydrates is incubated with glucose. Many products were identified by gas chromatography of the derivatized reaction mixtures followed by mass spectroscopy of the individual chromatographic peaks. Galacto-, gluco-, or mannopyranosyl rings appear to be present at the nonreducing ends of all the disaccharides produced. Molecules linked through primary hydroxyl groups have the highest equilibrium constants of all products formed, since these bonds are thermodynamically favored. However, glucoamylase is capable of forming bonds with many available hydroxyl groups, as previously demonstrated when it was incubated with glucose alone. Formation rates of different bonds linking different residues vary widely. These results demonstrate that glucoamylase has a wide selectivity toward residues it will condense into disaccharides and toward bonds it will form between them. ©

Modulation of cancer cell proliferation by unusually produced β(1-6) linked Mannan-oligosaccharides and β(1-6) linked Galactooligosaccharides using β–galactosidase from Aspergillus oryzae

“…Mannose is a well-known substrate in mannosidases. Mannosidases are also known to produce monno-oligosaccharides by transglycosylation or reverse hydrolysis (Bubb, 2003;Pestlin et al, 1997). Unlike GOS, the formation of MOS in this reaction is relatively slower, as shown in their relative rates of formation in Fig.…”