Comparative studies of two α-amylases acting on two Sorghum hybrids starches (Montecillos hybrid 2 and 3) and their significant differences in their catalytic activities

Starchy substances constitute the major part of the human diet for most people in the world. α-Amylases are widely distributed enzymes that initiate the hydrolysis of starch into low molecular weight maltodextrins. The effect of pH on the rate of hydrolysis of both sorghum (Montecillo 2 and 3) hybrids starches by industrial bacterial amylase (IBA) and Aspergillus oryzae α-amylase(AOA) was studied. This result suggests that both IBA and AOA α-amylases had slightly high affinity for soluble starch of sorghum Montecillo 3 and 1 hybrids, respectively. Using the structural information available, the theoretical pKa values of its ionizable residues directly involved in the catalytic region were determined. Both our experimental data and prediction studies indicated that the average pKa values are in good agreement.