We have isolated a cDNA clone from a Xenopus laevis tadpole cDNA library which probably codes for the large subunit of glutathione synthetase. The corresponding protein comprises 474 amino acids and shows a significant homology with the large subunit of glutathione synthetase of Schizosaccharomyces pombe. RNase protection experiments revealed that the gene is transcribed during oogenesis and that zygotic expression starts after midblastula transition. Transcripts are also detected in various adult tissues suggesting an ubiquitous distribution of the corresponding protein.