Compositions and methods for conferring tolerance to glyphosate in bacteria, plants, plant cells, tissues and seeds are provided. Compositions include a novel class of EPSPS enzymes, designated Class III, and polynucleotides encoding such enzymes, vectors comprising those polynucleotides, and host cells comprising the vectors. The novel proteins comprise at least one sequence domain selected from the Class III domains provided herein. These sequence domains can be used to identify EPSP synthases with glyphosate resistance activity.