We characterized the yeast gamma-glutamyl kinase important for proline biosynthesis. Asp154 and Ile150 were involved in the affinity with glutamate as well as proline. The Asp154Asn and Ile150Thr mutants had increased thermostability, in addition to desensitization to proline. Deletion of a C-terminal domain dramatically decreased the reaction rate and stability. (C) 2013, The Society for Biotechnology, Japan. All rights reserved.