Abstract: -Glutamyl cyclotransferase (GGCT) is one of the key enzymes that contribute to the -glutamyl cycle and regulate the glutathione metabolism. Disturbance in the glutathione metabolism is usually associated with damages in central nervous system. Here we explored the role of GGCT in the early development of zebrafish. First we used Morpholino (MO) to reduce the expression of GGCT at early developmental stages, and we found that compared to the wild type the treated embryos showed retarded brain development, shorter body sizes and cardiac ventricle dropsy. The results of whole mount in situ hybridization showed that the expression patterns of the brain development marker genes (shh, wnt8b, fgf8) were also changed. These abnormal phenotypes could be partially rescued by the co-injection of ggct-mRNA with GGCT-MO. Next we applied chemical inhibitors to antagonize other two important enzymes in -glutamyl cycle, -Glutamyl transpeptidase and 5 hydroxyproline enzyme. The zebrafish embryos injected with the inhibitors showed similar abnormalities that mimicked the GGCT-MO treatment. Finally we measured the concentration of GSH/GSSG in these embryos and observed a significant decrease in GSH concentration when the metabolic cycle was blocked. These results indicated that GGCT might play an important role in the early development of zebrafish through its function in the -glutamyl cycle.