The enzyme N-myristoyltransferase (NMT) or glycylpeptide N-tetradecanoyltransferase is responsible for the irreversible addition of a myristoyl group to N-terminal or internal glycine residues of proteins. This modification can occur co-translationally or post-translationally. In vertebrates, this modification is carried about by two NMTs, NMT1 and NMT2, both of which are members of the GCN5 acetyltransferase superfamily.