Some Enzyme Properties of Raw Starch Digesting Amylases fromStreptomyces sp. No. 4

Streptomyces sp. No. 4 produce two forms of amylase that attack raw cassava starch. Both forms, amylase-1 and amylase-2, were purified by starch adsorption, affinity chromatography, and ion exchange chromatography. The molecular weights of amylase-1 and amylase-2 as determined by SDS-PAGE were 56 kD and 77 kD, respectively. Optimal enzyme activities occurred at pH 5.5 and at 50°C for amylase-1 and at 45°C for amylase-2. The activation energy of amylase-1 and amylase-2 were 67 and 42 kJ/mol, respectively. Hg2+ and pCMB inhibited both enzymes, whereas 2-mercaptoethanol activated only amylase-2. EDTA inhibited amylase-1 but activated amylase-2. The main product of hydrolysis of raw cassava starch by amylase-1 was maltose, followed by maltotriose, maltotetraose and dextrin. Amylase-2 cleaved raw cassava starch to produce glucose and maltose as main products. Both amylase-1 and amylase-2 are α-amylases, as shown by the fast disappearance of iodine staining, the corresponding reaction products and the ability of both enzymes to hydrolyze crosslinked blue starch.