Transferases;
Transferring one-carbon groups;
Methyltransferases
BRITE hierarchy

S-adenosyl-L-methionine:N-terminal-(A,P,S)PK-[protein] methyltransferase

(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]

S-adenosyl-L-methionine [CPD:C00019];
N-terminal-(A,S)PK-[protein];
N-terminal-N-methyl-N-(A,S)PK-[protein];
N-terminal-N,N-dimethyl-N-(A,S)PK-serine-[protein];
N-terminal-PPK-[protein];
N-terminal-N-methyl-N-PPK-[protein]

This enzyme methylates the N-terminus of target proteins containing the N-terminal motif [Ala/Pro/Ser]-Pro-Lys after the initiator L-methionine is cleaved. When the terminal amino acid is L-proline, the enzyme catalyses two successive methylations of its alpha-amino group. When the first amino acid is either L-alanine or L-serine, the enzyme catalyses three successive methylations.
The Pro-Lys in positions 2-3 cannot be exchanged for other amino acids [1,2].

EC 2.1.1.244 created 2012

1  [PMID:20481588]

2  [PMID:20668449]