Protein N-terminal methyltransferase (EC 2.1.1.244, NMT1 (gene), METTL11A (gene)) is an enzyme with systematic name S-adenosyl-L-methionine:N-terminal-(A,P,S)PK-(protein) methyltransferase. This enzyme catalyses the following chemical reaction
(1) 3 S-adenosyl-L-methionine + N-terminal-(A,S)PK-[protein]
⇌ 3 S-adenosyl-L-homocysteine + N-terminal-N,N,N-trimethyl-N-(A,S)PK-[protein] (overall reaction)(1a) S-adenosyl-L-methionine + N-terminal-(A,S)PK-[protein]
⇌ S-adenosyl-L-homocysteine + N-terminal-N-methyl-N-(A,S)PK-[protein](1b) S-adenosyl-L-methionine + N-terminal-N-methyl-N-(A,S)PK-[protein]
⇌ S-adenosyl-L-homocysteine + N-terminal-N,N-dimethyl-N-(A,S)PK-[protein](1c) S-adenosyl-L-methionine + N-terminal-N,N-dimethyl-N-(A,S)PK-serine-[protein]
⇌ S-adenosyl-L-homocysteine + N-terminal-N,N,N-trimethyl-N-(A,S)PK-[protein](2) 2 S-adenosyl-L-methionine + N-terminal-PPK-[protein]
⇌ 2 S-adenosyl-L-homocysteine + N-terminal-N,N-dimethyl-N-PPK-[protein] (overall reaction)(2a) S-adenosyl-L-methionine + N-terminal-PPK-[protein]
⇌ S-adenosyl-L-homocysteine + N-terminal-N-methyl-N-PPK-[protein](2b) S-adenosyl-L-methionine + N-terminal-N-methyl-N-PPK-[protein]
⇌ S-adenosyl-L-homocysteine + N-terminal-N,N-dimethyl-N-PPK-[protein]
This enzyme methylates the N-terminus of target proteins containing the N-terminal motif [Ala/Pro/Ser]-Pro-Lys.
