The invention provides transgenic corn seed, which expresses a gene encoding a double mutant of the E. coli glgC gene in endosperm plastids, wherein the mutant protein has a proline to aspartic acid substitution at amino acid 295 and a glutamic acid to lysine substitution at amino acid 296. The transgenic corn seed of the invention is characterized by enhanced levels of a number of amino acids and oil, when compared to isogenic corn seed, which does not express the transgene in an endosperm plastid. However, the amount of starch in the transgenic corn seed of the invention is decreased or unchanged when compared to the amount of starch in the isogenic control corn seed.