TY - JOUR
T1 - Determination of the transgalactosylation activity of Aspergillus oryzae β-galactosidase
T2 - Effect of pH, temperature, and galactose and glucose concentrations
AU - Vera, Carlos
AU - Guerrero, Cecilia
AU - Illanes, Andrés
N1 - Funding Information:
This work was financially supported by Chilean Fondecyt Grants 1100050 and 1080118 , and Grant 037-112/2008 from the Pontificia Universidad Católica de Valparaíso . The work was performed within the framework of CYTED-D Enznut and NovelProbio networks. We acknowledge the generous donations of A. oryzae β-galactosidase by Enzyme Development Corporation (New York, USA).
PY - 2011/5/1
Y1 - 2011/5/1
N2 - The catalytic potential of β-galactosidase is usually determined by its hydrolytic activity over natural or synthetic substrates. However, this method poorly predicts enzyme behavior when transglycosylation instead of hydrolysis is being performed. A system for determining the transgalactosylation activity of β-galactosidase from Aspergillus oryzae was developed, and its activity was determined under conditions for the synthesis of galacto-oligosaccharides and lactulose. Transgalactosylation activity increased with temperature up to 55 °C while the effect of pH was mild in the range from pH 2.5 to 5.5, decreasing at higher values. The effect of glucose and galactose on transgalactosylation activity was also assessed both in the reactions for the synthesis of galacto-oligosaccharides and lactulose and also in the reaction of hydrolysis of o-nitrophenyl β-d-galactopiranoside. Galactose was a competitive inhibitor and its effect was stronger in the reactions of transgalactosylation than in the reaction of hydrolysis. Glucose was a mild activator of β-galactosidase in the reaction of hydrolysis, but its mechanism of action was more complex in the reactions of transgalactosylation, having this positive effect only at low concentrations while acting as an inhibitor at high concentrations. This information is relevant to properly assess the effect of monosaccharides during the reactions of the synthesis of lactose-derived oligosaccharides, such as galacto-oligosaccharides and lactulose.
AB - The catalytic potential of β-galactosidase is usually determined by its hydrolytic activity over natural or synthetic substrates. However, this method poorly predicts enzyme behavior when transglycosylation instead of hydrolysis is being performed. A system for determining the transgalactosylation activity of β-galactosidase from Aspergillus oryzae was developed, and its activity was determined under conditions for the synthesis of galacto-oligosaccharides and lactulose. Transgalactosylation activity increased with temperature up to 55 °C while the effect of pH was mild in the range from pH 2.5 to 5.5, decreasing at higher values. The effect of glucose and galactose on transgalactosylation activity was also assessed both in the reactions for the synthesis of galacto-oligosaccharides and lactulose and also in the reaction of hydrolysis of o-nitrophenyl β-d-galactopiranoside. Galactose was a competitive inhibitor and its effect was stronger in the reactions of transgalactosylation than in the reaction of hydrolysis. Glucose was a mild activator of β-galactosidase in the reaction of hydrolysis, but its mechanism of action was more complex in the reactions of transgalactosylation, having this positive effect only at low concentrations while acting as an inhibitor at high concentrations. This information is relevant to properly assess the effect of monosaccharides during the reactions of the synthesis of lactose-derived oligosaccharides, such as galacto-oligosaccharides and lactulose.
KW - Galacto-oligosaccharides
KW - Inhibition
KW - Lactulose
KW - Transgalatosylation
KW - β-Galactosidase
UR - http://www.scopus.com/inward/record.url?scp=79953315791&partnerID=8YFLogxK
U2 - 10.1016/j.carres.2011.01.030
DO - 10.1016/j.carres.2011.01.030
M3 - Article
C2 - 21439558
AN - SCOPUS:79953315791
VL - 346
SP - 745
EP - 752
JO - Carbohydrate Research
JF - Carbohydrate Research
SN - 0008-6215
IS - 6
ER -