The subject invention concerns chimeric AGP subunit proteins and polynucleotides that encode the chimeric proteins. The subject invention provides for mutant AGP enzymes comprising a chimeric subunit of the invention that are less sensitive to inorganic phosphate than wild type AGP enzymes. In one embodiment, the AGP subunit is a small subunit of a plant AGP enzyme. The subject invention also concerns plants comprising a polynucleotide encoding a chimeric AGP subunit protein of the invention. The subject invention also concerns methods for producing a plant comprising a polynucleotide of the present invention. Plants produced according to the invention comprise AGP enzymes that are less sensitive to inorganic phosphate than wild type AGP enzyme.