Ggt5, short for Gamma-glutamyltransferase 5, is one of the two members in the GGT family. It plays a crucial role in oxidative regulation, inflammation promotion, and drug metabolism. Ggt5 is also involved in glutathione (GSH) metabolism and may support lymphocyte guidance through catabolism of S-geranylgeranyl-l-glutathione [4,2].

In gastric cancer, high Ggt5 expression is significantly associated with poor overall survival, histological differentiation, T stage, histological type, and histologic grade. Down-regulation of Ggt5 in vitro hampers the proliferation and migration of gastric cancer cell lines, and it may be involved in the regulation of vascular development, angiogenesis, cell motility and migration, possibly through the PI3K/AKT-MAPK-MMPs pathways [1,3,5].

In addition, in Alzheimer's disease, Ggt5 expression in cerebrovascular endothelial cells is inversely associated with the disease pathogenesis, and its overexpression mitigates cognitive deficits in APP/PS1 mice [6]. Also, in testicular steroidogenesis, overexpression of Ggt5 impairs the process by deregulating local oxidative stress [7].

In conclusion, Ggt5 has diverse functions in different biological processes and diseases. In gastric cancer, it shows potential as a prognostic biomarker and therapeutic target. In Alzheimer's disease, it may serve as a biomarker and a therapeutic target, while in testicular steroidogenesis, it affects the process through oxidative stress regulation. These findings from different research models, including in vitro cell-line studies and in vivo mouse models, help to understand the role of Ggt5 in various biological contexts and disease conditions.