_EC 2.1.1.37 Dna (cytosine-5-)-methyltransferase. 54 PDB entries  
EC 2.-.-.- Transferases. [16,521 PDB entries]
EC 2.1.-.- Transferring one-carbon groups. [1,566 PDB entries]
EC 2.1.1.- Methyltransferases. [1,227 PDB entries]
EC 2.1.1.37 Dna (cytosine-5-)-methyltransferase. [54 PDB entries]    
10mh

Reaction: S-adenosyl-L-methionine + Dna = S-adenosyl-L-homocysteine + Dna containing 5-methylcytosine.
 


S-adenosyl-L-methionine
+
DNA
=
S-adenosyl-L-homocysteine
+
DNA containing 5-methylcytosine
Molecule diagrams generated from .mol files obtained from the KEGG ftp site.

Other name(s): Cytosine 5-methyltransferase. Cytosine Dna methylase. Cytosine Dna methyltransferase. Cytosine-specific Dna methyltransferase. Deoxyribonucleate methylase. Deoxyribonucleate methyltransferase. Deoxyribonucleic (cytosine-5-)-methyltransferase. Deoxyribonucleic acid (cytosine-5-)-methyltransferase. Deoxyribonucleic acid methylase. Deoxyribonucleic acid methyltransferase.
Comments: See the Rebase database for a complete list of these enzymes: http://rebase.neb.com/rebase/ Formerly Ec 2.1.1.73.
Links:   [IntEnz]   [ExPASy]   [KEGG]  

There are 54 PDB entries in enzyme class E.C.2.1.1.37

  PDB code Protein
10mh
Ternary structure of hhai methyltransferase with adohcy and hemimethylated DNA containing 5,6-dihydro-5-azacytosine at the target
Source: Synthetic: yes. Haemophilus haemolyticus. Organism_taxid: 726. Expressed in: escherichia coli. Expression_system_taxid: 562
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
1dct
DNA (cytosine-5) methylase from haeiii covalently bound to DNA
Source: Synthetic: yes. Haemophilus influenzae biotype aegyptius. Organism_taxid: 725. Strain: biotype aegyptius
Chains: A, B (324 residues) CATH domains: 3.40.50.150 3.90.120.10
1fjx
Structure of ternary complex of hhai methyltransferase mutant (t250g) in complex with DNA and adohcy
Source: Synthetic: yes. Other_details: chemically synthesized. Haemophilus haemolyticus. Organism_taxid: 726. Expressed in: escherichia coli. Expression_system_taxid: 562
Chain: A (327 residues) CATH domains: 3.90.120.10 3.40.50.150
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
1hmy
Crystal structure of the hhai DNA methyltransferase complexe adenosyl-l-methionine
Source: Haemophilus haemolyticus. Organism_taxid: 726
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAM corresponds to enzyme reactant S-adenosyl-L-methionine
1khc
Crystal structure of the pwwp domain of mammalian DNA methyltransferase dnmt3b
Source: Mus musculus. House mouse. Organism_taxid: 10090. Gene: dnmt3b. Expressed in: escherichia coli bl21(de3). Expression_system_taxid: 469008.
Chain: A (137 residues) CATH domains: 2.30.30.160 1.10.720.50
1m0e
Zebularine: a novel DNA methylation inhibitor that forms a covalent complex with DNA methyltransferase
Source: Synthetic: yes. Haemophilus haemolyticus. Organism_taxid: 726. Expressed in: escherichia coli. Expression_system_taxid: 562
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
1mht
Covalent ternary structure of hhai methyltransferase, DNA and s-adenosyl-l-homocysteine
Source: Synthetic: yes. Haemophilus haemolyticus. Organism_taxid: 726
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
1skm
Hhai methyltransferase in complex with DNA containing an abasic south carbocyclic sugar at its target site
Source: Synthetic: yes. Haemophilus haemolyticus. Organism_taxid: 726. Gene: hhaim. Expressed in: escherichia coli. Expression_system_taxid: 562
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
1svu
Structure of the q237w mutant of hhai DNA methyltransferase: an insight into protein-protein interactions
Source: Haemophilus haemolyticus. Organism_taxid: 726. Gene: hhaim. Expressed in: escherichia coli. Expression_system_taxid: 562
Chains: A, B (307 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
2c7o
Hhai DNA methyltransferase complex with 13mer oligonucleotide containing 2-aminopurine adjacent to the target base (pcgc:gmgc) and sah
Source: Haemophilus haemolyticus. Organism_taxid: 726. Expressed in: escherichia coli. Expression_system_taxid: 562. Synthetic: yes. Synthetic construct. Organism_taxid: 32630. Synthetic: yes organism_taxid: 32630
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
2c7p
Hhai DNA methyltransferase complex with oligonucleotide cont 2-aminopurine opposite to the target base (gcgc:gmpc) and s
Source: Haemophilus haemolyticus. Organism_taxid: 726. Expressed in: escherichia coli. Expression_system_taxid: 562. Synthetic: yes. Synthetic construct. Organism_taxid: 32630. Organism_taxid: 32630
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
2c7q
Hhai DNA methyltransferase complex with oligonucleotide containing 2-aminopurine outside the recognition sequence (paired with g) and sah
Source: Haemophilus haemolyticus. Organism_taxid: 726. Expressed in: escherichia coli. Expression_system_taxid: 562. Synthetic: yes. Synthetic construct. Organism_taxid: 32630. Organism_taxid: 32630
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
2c7r
Hhai DNA methyltransferase (t250g mutant) complex with oligonucleotide containing 2-aminopurine as a target base (gpgc:gmgc) and sah
Source: Haemophilus haemolyticus. Organism_taxid: 726. Expressed in: escherichia coli. Expression_system_taxid: 562. Synthetic: yes. Synthetic construct. Organism_taxid: 32630. Organism_taxid: 32630
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
2hmy
Binary complex of hhai methyltransferase with adomet formed in the presence of a short nonpsecific DNA oligonucleotide
Source: Haemophilus haemolyticus. Organism_taxid: 726. Expressed in: escherichia coli. Expression_system_taxid: 562
Chain: B (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAM corresponds to enzyme reactant S-adenosyl-L-methionine
2hr1
Ternary structure of wt m.Hhai c5-cytosine DNA methyltransferase with unmodified DNA and adohcy
Source: Synthetic: yes. Haemophilus parahaemolyticus. Organism_taxid: 735. Gene: hhaim. Expressed in: escherichia coli. Expression_system_taxid: 562.
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
2i9k
Engineered extrahelical base destabilization enhances sequence discrimination of DNA methyltransferase m.Hhai
Source: Synthetic: yes. Haemophilus haemolyticus. Organism_taxid: 726. Gene: hhaim. Expressed in: escherichia coli. Expression_system_taxid: 562.
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
2uyc
Hhai DNA methyltransferase r163n mutant complex with 13mer gcgc-gmgc oligonucleotide and sah
Source: Haemophilus haemolyticus. Organism_taxid: 726. Expressed in: eschericia coli. Expression_system_taxid: 562. Synthetic: yes. Synthetic: yes
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
2uyh
Hhai DNA methyltransferase s87q-q237s mutant complex with 13mer gcgc-gmgc oligonucleotide and sah
Source: Haemophilus haemolyticus. Organism_taxid: 726. Expressed in: escherichia coli. Expression_system_taxid: 562. Synthetic: yes. Synthetic: yes
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
2uz4
Hhai DNA methyltransferase r165n mutant complex with 13mer gcgc-gmgc oligonucleotide and sah
Source: Haemophilus parahaemolyticus. Organism_taxid: 735. Expressed in: escherichia coli. Expression_system_taxid: 562. Synthetic: yes. Synthetic: yes
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
2z6a
S-adenosyl-l-methionine-dependent methyl transfer: observable precatalytic intermediates during DNA cytosine methylation
Source: Haemophilus parahaemolyticus. Organism_taxid: 735. Gene: hhaim. Expressed in: escherichia coli. Expression_system_taxid: 562. Synthetic: yes. Other_details: synthetic construction. Other_details: synthetic construction
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
2z6q
Ternary structure of arg165ala m.Hhai c5-cytosine DNA methyltransferase with unmodified DNA and adohcy
Source: Haemophilus parahaemolyticus. Organism_taxid: 735. Gene: hhaim. Expressed in: escherichia coli. Expression_system_taxid: 562. Synthetic: yes. Other_details: synthetic construction. Other_details: synthetic construction
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
2z6u
Ternary structure of the glu119ala m.Hhai, c5-cytosine DNA methyltransferase, with unmodified DNA and adohcy
Source: Haemophilus parahaemolyticus. Organism_taxid: 735. Gene: hhaim. Expressed in: escherichia coli. Expression_system_taxid: 562. Synthetic: yes. Other_details: synthetic construction. Other_details: synthetic construction
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
2zcj
Ternary structure of the glu119gln m.Hhai, c5-cytosine DNA methyltransferase, with unmodified DNA and adohcy
Source: Haemophilus parahaemolyticus. Organism_taxid: 735. Gene: hhaim. Expressed in: escherichia coli. Expression_system_taxid: 562. Synthetic: yes. Other_details: synthetic construction. Other_details: synthetic construction
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH is 96.00% similar to enzyme reactant S-adenosyl-L-methionine
3a1a
Crystal structure of the dnmt3a add domain
Source: Homo sapiens. Human. Organism_taxid: 9606. Gene: dnmt3a. Expressed in: escherichia coli. Expression_system_taxid: 469008.
Chain: A (132 residues)
3a1b
Crystal structure of the dnmt3a add domain in complex with h
Source: Homo sapiens. Human. Organism_taxid: 9606. Expressed in: escherichia coli. Expression_system_taxid: 469008.
Chain: A (148 residues)
3av4
Crystal structure of mouse DNA methyltransferase 1
Source: Mus musculus. Mouse. Organism_taxid: 10090. Gene: dnmt1, dnmt, met1, uim. Expressed in: spodoptera frugiperda. Expression_system_taxid: 7108. Expression_system_cell_line: sf9.
Chain: A (1140 residues)
3av5
Crystal structure of mouse DNA methyltransferase 1 with adoh
Source: Mus musculus. Mouse. Organism_taxid: 10090. Gene: dnmt1, dnmt, met1, uim. Expressed in: spodoptera frugiperda. Expression_system_taxid: 7108. Expression_system_cell_line: sf9.
Chain: A (1139 residues)
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
3av6
Crystal structure of mouse DNA methyltransferase 1 with adom
Source: Mus musculus. Mouse. Organism_taxid: 10090. Gene: dnmt1, dnmt, met1, uim. Expressed in: spodoptera frugiperda. Expression_system_taxid: 7108. Expression_system_cell_line: sf9.
Chain: A (1135 residues)
Bound ligand:   Het Group SAM corresponds to enzyme reactant S-adenosyl-L-methionine
3eeo
M. Hhai co-crystallized with synthetic dsdna containing a propane diol in place of the deoxycytidine residue targeted for methylation.
Source: Synthetic: yes. Haemophilus parahaemolyticus. Organism_taxid: 735. Gene: hhaim. Expressed in: escherichia coli. Expression_system_taxid: 562
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAM corresponds to enzyme reactant S-adenosyl-L-methionine
3epz
Structure of the replication foci-targeting sequence of huma cytosine methyltransferase dnmt1
Source: Homo sapiens. Human. Organism_taxid: 9606. Gene: aim, cxx9, cxxc9, dnmt, dnmt1. Expressed in: escherichia coli. Expression_system_taxid: 562.
Chains: A, B (227 residues) CATH domains: 0.0.0.0 0.0.0.0
3flg
The pwwp domain of human DNA (cytosine-5-)-methyltransferase 3 beta
Source: Homo sapiens. Human. Organism_taxid: 9606. Gene: dnmt3b. Expressed in: escherichia coli. Expression_system_taxid: 562
Chain: A (135 residues) CATH domains: 2.30.30.160 1.10.720.50
3g7u
Crystal structure of putative DNA modification methyltransfe encoded within prophage cp-933r (e.Coli)
Source: Escherichia coli o157:h7 edl933. Organism_taxid: 155864. Strain: o157:h7 edl933 / ehec. Atcc: 700927. Gene: ecs1953, z2389. Expressed in: escherichia coli. Expression_system_taxid: 562.
Chain: A (348 residues) CATH domain: 3.40.50.150
3llr
Crystal structure of the pwwp domain of human DNA (cytosine- methyltransferase 3 alpha
Source: Homo sapiens. Human. Organism_taxid: 9606. Gene: dnmt3a. Expressed in: escherichia coli. Expression_system_taxid: 562
Chains: A, B, C, D, E (131 residues) CATH domains: 2.30.30.160 1.10.720.50
3lx6
Crystal structure of putative DNA cytosine methylase from sh flexneri 2a str. 2457t
Source: Shigella flexneri 2a. Organism_taxid: 198215. Strain: 2457t. Gene: dcm, s2100, sf2005, sf2457t_1495. Expressed in: escherichia coli. Expression_system_taxid: 469008.
Chains: A, B (368 residues) CATH domain: 3.40.50.150
3me5
Crystal structure of putative DNA cytosine methylase from sh flexneri 2a str. 2457t
Source: Shigella flexneri 2a. Organism_taxid: 198215. Strain: 2457t. Gene: aap17376.1, dcm, s2100, sf2005, sf2457t_1495. Expressed in: escherichia coli. Expression_system_taxid: 469008.
Chain: A (414 residues) CATH domains: Unassigned 3.40.50.150
3mht
Ternary structure of hhai methyltransferase with unmodified DNA and adohcy
Source: Synthetic: yes. Haemophilus haemolyticus. Organism_taxid: 726
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
3pt6
Crystal structure of mouse dnmt1(650-1602) in complex with d
Source: Mus musculus. Mouse. Organism_taxid: 10090. Gene: dnmt1, dnmt, met1, uim. Expressed in: escherichia coli. Expression_system_taxid: 469008. Synthetic: yes. Synthetic: yes
Chains: A, B (914 residues)
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
3pt9
Crystal structure of mouse dnmt1(731-1602) in the free state
Source: Mus musculus. Mouse. Organism_taxid: 10090. Gene: dnmt1, dnmt, met1, uim. Expressed in: escherichia coli. Expression_system_taxid: 469008.
Chain: A (824 residues) CATH domains: 0.0.0.0 0.0.0.0 0.0.0.0 0.0.0.0
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
3pta
Crystal structure of human dnmt1(646-1600) in complex with d
Source: Homo sapiens. Human. Organism_taxid: 9606. Gene: dnmt1, aim, cxxc9, dnmt. Expressed in: escherichia coli. Expression_system_taxid: 562. Synthetic: yes. Synthetic: yes
Chain: A (904 residues) CATH domains: Unassigned Unassigned Unassigned Unassigned 3.40.50.150
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
3qkj
The pwwp domain of human DNA (cytosine-5-)-methyltransferase complex with a bis-tris molecule
Source: Homo sapiens. Human. Organism_taxid: 9606. Expressed in: escherichia coli. Expression_system_taxid: 469008.
Chains: A, B, C, D (130 residues) CATH domains: 2.30.30.160 1.10.720.50
3qv2
Structure analysis of entamoeba histolytica methyltransferas
Source: Entamoeba histolytica. Organism_taxid: 5759. Gene: meth, ehi_069140. Expressed in: escherichia coli. Expression_system_taxid: 469008.
Chain: A (320 residues) CATH domains: 0.0.0.0 0.0.0.0
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
3svm
Human mpp8 - human dnmt3ak47me2 peptide
Source: Homo sapiens. Human. Organism_taxid: 9606. Gene: mphosph8, mpp8. Expressed in: escherichia coli. Expression_system_taxid: 562. Synthetic: yes. Organism_taxid: 9606
Chain: P (12 residues)
3swr
Structure of human dnmt1 (601-1600) in complex with sinefung
Source: Homo sapiens. Human. Organism_taxid: 9606. Gene: dnmt1, aim, cxxc9, dnmt. Expressed in: escherichia coli. Expression_system_taxid: 562.
Chain: A (965 residues)
Bound ligand:   Het Group SFG is 51.43% similar to enzyme product S-adenosyl-L-methionine
3ubt
Crystal structure of c71s mutant of DNA cytosine-5 methyltra m.Haeiii bound to DNA
Source: Haemophilus aegyptius. Koch-weeks bacillus. Organism_taxid: 197575. Gene: haeiiim. Expressed in: escherichia coli. Expression_system_taxid: 562. Synthetic: yes
Chains: Y, A, B (328 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group ATP is 58.06% similar to enzyme product S-adenosyl-L-methionine
4da4
Structure of mouse dnmt1 (731-1602) bound to hemimethylated
Source: Mus musculus. Mouse. Organism_taxid: 10090. Gene: dnmt1, dnmt, met1, uim. Expressed in: escherichia coli. Expression_system_taxid: 469008. Synthetic: yes. Other_details: chemically synthesized. Other_details: chemically synthesized
Chains: A, B (834 residues) CATH domains: 0.0.0.0 0.0.0.0 0.0.0.0 0.0.0.0
4fsx
Crystal structure of se-substituted zea mays zmet2 in comple
Source: Zea mays. Maize. Organism_taxid: 4577. Gene: met2a, zmet2. Expressed in: escherichia coli. Expression_system_taxid: 469008.
Chains: A, B (680 residues) CATH domains: 0.0.0.0 0.0.0.0 0.0.0.0
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
4ft2
Crystal structure of zea mays zmet2 in complex h3(1-15)k9me2 and sah
Source: Zea mays. Maize. Organism_taxid: 4577. Gene: met2a, zmet2. Expressed in: escherichia coli. Expression_system_taxid: 469008. Synthetic: yes. Other_details: h3 peptide was synthesized
Chains: A, B (674 residues) CATH domains: 0.0.0.0 0.0.0.0 0.0.0.0
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
4ft4
Crystal structure of zea mays zmet2 in complex h3(1-32)k9me2 and sah
Source: Zea mays. Maize. Organism_taxid: 4577. Gene: met2a, zmet2. Expressed in: escherichia coli. Expression_system_taxid: 469008. Synthetic: yes. Other_details: h3(1-32)k9me2 peptide was synthesized
Chains: B, A (693 residues) CATH domains: 0.0.0.0 0.0.0.0 0.0.0.0
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
4mht
Ternary structure of hhai methyltransferase with native DNA and adohcy
Source: Synthetic: yes. Haemophilus haemolyticus. Organism_taxid: 726
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
5mht
Ternary structure of hhai methyltransferase with hemimethylated DNA and adohcy
Source: Synthetic: yes. Haemophilus haemolyticus. Organism_taxid: 726
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
6mht
Ternary structure of hhai methyltransferase with adohcy and DNA containing 4'-thio-2'deoxycytidine at the target
Source: Haemophilus haemolyticus. Organism_taxid: 726. Expressed in: escherichia coli. Expression_system_taxid: 562. Organism_taxid: 726
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAM corresponds to enzyme reactant S-adenosyl-L-methionine
7mht
Cytosine-specific methyltransferase hhai/DNA complex
Source: Synthetic: yes. Haemophilus haemolyticus. Organism_taxid: 726. Expressed in: escherichia coli. Expression_system_taxid: 562
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
8mht
Cytosine-specific methyltransferase hhai/DNA complex
Source: Synthetic: yes. Haemophilus haemolyticus. Organism_taxid: 726. Expressed in: escherichia coli. Expression_system_taxid: 562
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine
9mht
Cytosine-specific methyltransferase hhai/DNA complex
Source: Synthetic: yes. Haemophilus haemolyticus. Organism_taxid: 726. Expressed in: escherichia coli. Expression_system_taxid: 562
Chain: A (327 residues) CATH domains: 3.40.50.150 3.90.120.10
Bound ligand:   Het Group SAH corresponds to enzyme product S-adenosyl-L-methionine