The present invention provides engineered guanylate kinase (GK) enzymes, polypeptides having GK activity, and polynucleotides encoding these enzymes, as well as vectors and host cells comprising these polynucleotides and polypeptides. Methods for producing GK enzymes are also provided. The present invention further provides compositions comprising the GK enzymes and methods of using the engineered GK enzymes. The present invention finds particular use in the production of pharmaceutical compounds.