Preferential And Rapid Degradation Of Raw Rice Starch By A New α-Amylase AmyP From Marine Microorganism

a-Amylases are ubiquitous in distribution, with plants, animals, and microo rganisms, bacteria and fungi being the predominant sources and it is an import ant starch hydrolyzing enzyme. a-amylases are among the most important com mercial enzymes in industry, they are widely applied in starch processing, etha nol producing, pharmaceutics, papers, Food manufacturing and other industrial field. A gene encoded a starch-hydrolyzing enzyme was isolated from a marine metagenomic library and over-expressed in Escherichia coli in the preliminary work, it is belongs to the recently classified glycoside hydrolase subfamily GH1337, this is the first α-Amylases with the ability of raw-starch-hydrolysis en zyme screened from marine bacteria.The degradation ability of AmyP on a broad range of raw starch granules were examined at40℃and pH7.5. AmyP is efficient in hydrolyzing all raw st arches tested from terrestrial plants such as rice, wheat, corn, potato, potatoes, peas, mung beans etc. However, it is surprising that the common polysacchari des in the marine such as fucoidan, laminarin, carrageenan, alginic acid, and chitin, none of them could serve as substrates for AmyP. In the research of A myP, with respect to the raw starch degrading enzymes which have been repor ted before, there are two significant characteristics quite different from those of any other previously isolated raw starch-degrading a-amylases. First, its signific ant preference degradation rice raw starch and the specific activity of raw rices tarch was reached118.5U/mg, which was much higher than other types of star ch. Secondly, AmyP is capable of digesting raw rice starch with a very rapid speed of hydrolysis. The hydrolysis occurred during the early2h for1%conce ntration and1h for8%,the most efficient hydrolysis time was less than half an hour. This Preferential and rapid degradation of raw rice starch has never bee n described in reported a-amylases, This unique degradation ability leads the AmyP with great potential in rice starch processing. However, the highly efficie nt degradation of short duration,leading to the final hydrolysis efficiency is not very high. In order to explore the reasons, we research from three aspects, the stability of the enzyme, product inhibition and substrate changes, Respectively. Discovered hindered AmyP further degraded starch due to the substrate, and most likely due to the micro structure of the substrate surface changes that is not conducive to the reaction.This is the first biochemical characterization of the raw starch-degrading a bility of an a-amylase of family GH13₃7. The specific ability towards raw ric e starch has never been described before, This discovery not only to deepen p eople’s understanding of GH13₃7subfamily, but alsao makes AmyP a promisi ng candidate for use as a novel enzyme in rice starch processing.