GATM (glycine amidinotransferase) is a mitochondrial transamidinase that catalyzes the rate-limiting step of creatine biosynthesis by transferring the amidino group from L-arginine to glycine, generating guanidinoacetate 12. Beyond glycine, GATM can aminidinoylate other acceptor metabolites including beta-alanine, GABA, and taurine 3. The resulting creatine serves as an ATP energy source in tissues with high metabolic demands, particularly skeletal muscle, heart, and brain 4. GATM exhibits tissue-specific expression, showing higher levels in type 2 muscle fibers 5. Pathologically, GATM upregulation promotes cancer metastasis across multiple tumor types—colorectal, breast, and pancreatic cancers—through creatine-mediated activation of EMT pathways and Smad2/3 signaling 678. In glioblastoma, myeloid cells expressing GATM provide creatine to tumor cells in hypoxic niches, promoting growth 9. Conversely, reduced GATM expression associates with chr15 kidney disease progression, suggesting a protective role in renal function 1011. GATM mutations cause cerebral creatine deficiency syndrome 3. Given its dual role in both metabolic homeostasis and pathological processes, GATM represents a potential therapeutic target for cancer prevention and kidney disease management.