The function of Ensembl gene identifier ENSG00000171766 (GATM, glycine amidinotransferase) is as follows. Transamidinase that catalyzes the transfer of the amidino group of L-arginine onto the amino moiety of acceptor metabolites such as glycine, beta-alanine, gamma-aminobutyric acid (GABA) and taurine yielding the corresponding guanidine derivatives (PubMed:16820567, PubMed:27233232, PubMed:36543883, PubMed:3800397). Catalyzes the rate- limiting step of creatine biosynthesis, namely the transfer of the amidino group from L-arginine to glycine to generate guanidinoacetate, which is then methylated by GAMT to form creatine. Provides creatine as a source for ATP generation in tissues with high energy demands, in particular skeletal muscle, heart and brain (Probable) (PubMed:27233232, PubMed:36543883, PubMed:3800397, PubMed:9266688). {ECO:0000269|PubMed:16820567, ECO:0000269|PubMed:27233232, ECO:0000269|PubMed:36543883, ECO:0000269|PubMed:3800397, ECO:0000269|PubMed:9266688, ECO:0000305|PubMed:16820567}.