FUNCTION Adds a myristoyl group to the N-terminal glycine residue of certain cellular and viral proteins (PubMed:22865860, PubMed:32686708, PubMed:34999170, PubMed:25255805, PubMed:9353336, PubMed:9506952). Also able to mediate N-terminal lysine myristoylation of proteins: catalyzes myristoylation of ARF6 on both 'Gly-2' and 'Lys-3' (PubMed:32103017, PubMed:32111831). Lysine myristoylation is required to maintain ARF6 on membranes during the GTPase cycle (PubMed:32103017).CATALYTIC ACTIVITY N-terminal glycyl-[protein] + tetradecanoyl-CoA = CoA + H(+) + N-tetradecanoylglycyl-[protein]CATALYTIC ACTIVITY N-terminal glycyl-L-lysyl-[protein] + tetradecanoyl-CoA = CoA + H(+) + N-terminal glycyl-(N(6)-tetradecanoyl)-L-lysyl-[protein]BIOPHYSICOCHEMICAL PROPERTIES kcat is 0.41 sec(-1) with tetradecanoyl-CoA as substrate.INTERACTION Copurifies with ribosomes.ALTERNATIVE PRODUCTS Heart, gut, kidney, liver and placenta.SIMILARITY Belongs to the NMT family.