Fahad A. Al-Dhabaan
Department of Biology, Science and Humanities College,
Alquwayiyah, Shaqra University, Saudi Arabia.
The activity of a-glucosidase enzyme (EC 188.8.131.52) was inhibited by 40.3% by an extracellular inhibitory protein which isolated from the culture filtrate of Aspergillus brasiliensis ATCC-16404. The maximum activity of this protein and fungal mycelial dry weight were obtained at 28°C, 7 days, 6.5, 400 µl/ml, 140 rpm, and rice straw as the optimum incubation temperature, incubation period, pH value, inoculum size, agitation speed, and raw material respectively. The a-glucosidase inhibitory protein (AGIP) was purified and separated electrically as a single band at 40 KDa. There 17 amino acids of the purified protein were determined at different concentrations, where threonine has a highest percentage (90%) and aspartic acid has a lower percentage (24%). Kinetics of AGIP were determined, where Vmax, Km, kcat, and catalytic activity values were exactly calculated using Lineweaver-Burk plot compared with those of acarbose as an inhibitor standard. The maximum catalytic activity (7.808 M-1S-1) at 0.1 mg/mol was higher than that of acarbose (7.783 M-1S-1) at the same concentration.
Keywords: Antidiabetics, diabetes mellitus, enzyme kinetics, protein purification.