Identification and characterization of a novel alpha-amylase from maize endosperm

Abstract

SHE, a Starch Hydrolytic Enzyme active in maize endosperm ( Zea mays ), and the cDNA sequence encoding SHE are disclosed. The specificity of native, purified SHE is similar, in general terms, to previously known alpha-amylases. However, the activity of SHE toward amylopectin results in hydrolysis products that are distinctly different from those of other alpha-amylases. SHE, and its homologous equivalents in other plants such as rice, Arabidopsis , apple and potato, can be used in starch processing for generating different, e.g., larger sized, alpha-limit dextrins for industrial use, as compared to those generated by previously known alpha-amylases or other starch hydrolytic enzymes. In addition, modification of the expression of this enzyme in transgenic maize plants or in other transgenic organisms (including bacteria, yeast, and other plant species) can be useful for the generation of novel starch forms or altered starch metabolism.

19 . A method of processing starch comprising the steps of:
 providing a sample of starch to be processed; and   treating said sample of starch with an enzyme preparation comprising a protein, or polypeptide fragment thereof, encoded by a nucleic acid isolate able to hybridize under stringent conditions to the complement of a nucleic acid sequence encoding the SHE protein having the amino acid sequence shown in  FIGS. 9A and 9B  (SEQ ID NO:2).