Significant differences in the activities of α-amylases in the absence and presence of polyethylene glycol assayed on eight starches solubilized by two methods

Abstract

Starch is a reserve chemical source of the energy of the sun found in plants as a water-insoluble granule that differs in their chemical and physical properties, depending on the source. The granules can be solubilized by heating in water or by treatment with various reagents, such as 1M NaOH. α-Amylases are widely distributed enzymes that initiate the hydrolysis of starch into low molecular weight maltodextrins. We recently found that the activities of a single α-amylase on two different starches were significantly different. We then determined the activities of Bacillus amyloliquefaciens and porcine pancreas α-amylases, using eight different starches, solubilized by two methods: autoclaving at 121°C and 1M NaOH at 20°C. There were significant differences in the activities of both of the amylases on all eight of the starches. Previously, it had been found that polyethylene glycol (PEG) stabilized and activated the activities of both enzymes, using a soluble amylose as the substrate. Addition of PEG to the enzymes greatly increased the activities on the eight starches, but the activities still differed significantly. The different activities with the starches were hypothesized as differences in the amounts of secondary and tertiary structures that are partially retained when the different starches are solubilized; the activities on addition of PEG is hypothesized as the formation of highly active species from a series of less active forms.