Patent ID: 8362321

Claim:
A polynucleotide encoding a mutant maize endosperm AGPase large subunit protein, or a functional fragment of said protein that exhibits the same activity as the full-length AGPase large subunit protein, wherein said protein comprises an amino acid mutation of the cysteine at position 424 of the wild type maize endosperm AGPase large subunit protein, wherein said cysteine is replaced by an amino acid that confers increased enzymatic activity when said mutant AGPase large subunit protein is expressed to form an AGPase enzyme, or wherein said protein comprises an amino acid mutation of the serine amino acid at position 163 of the wild type maize endosperm AGPase large subunit protein, wherein said serine is replaced by an amino acid that confers increased heat stability of AGPase activity when said mutant AGPase large subunit protein is expressed to form an AGPase enzyme; or said protein comprises both of said amino acid mutations; and wherein said functional fragment comprises one or both of said amino acid mutations.