Patent ID: 7312378

Claim:
An isolated polynucleotide comprising a nucleotide sequence encoding a mutant large subunit of a plant ADP-glucose pyrophosphorylase (AGP) protein, or a biologically-active fragment of said mutant protein, wherein when said mutant large subunit protein is expressed to form a mutant ADP-glucose pyrophosphorylase enzyme, said mutant enzyme, or a biologically-active fragment of said mutant enzyme, exhibits increased heat stability relative to wild type ADP-glucose pyrophosphorylase enzyme, and wherein said mutant large subunit protein encoded by said polynucleotide comprises an amino acid mutation wherein the amino acid corresponding to the histidine at position 333 in the amino acid sequence of a wild type large subunit of ADP-glucose pyrophosphorylase polypeptide of maize is replaced by an amino acid that confers said increased heat stability on said mutant enzyme.