Synthesis of d-β-Glutamine from β-Glutamic Acid by Glutamine Synthetase

Abstract

SUMMARY Glutamine synthetase from sheep brain catalyzes the synthesis of n-/3-glutamine and u-fl-glutamylhydroxamic acid from fi- glutamic acid (P-aminoglutaric acid). The optical rotations of the N-acetyl derivatives of the enzymatically synthesized prod- ucts are equal and opposite to those of the corresponding L enzyme surface, replacement of the (Y hydrogen atom of n-glutamic acid by a methyl group would be expected to interfere with its attachment to the enzyme, while similar substitution of the 01 hydrogen atom of L-glutamic acid would not. isomers, which were obtained from 3-L-acetylamino-4-carbo- ethoxylbutanoic acid. The ability of glutamine synthetase to distinguish between the carboxyl groups of ,8-glutamic acid is considered in relation to other data on specificity of this en- zyme. A tentative explanation is proposed for the findings based on spatial similarity between extended conformations of L-glutamine and n-fi-glutamine. Acknowledgments-We are indebted to Dr. Daniel Wellner for many stimulating discussions and to Dr. Vaira Wellner Miss Joyce Tenczar for the purified glutamine synthetase used in these studies. REFERENCES 1.