Map Key
Generic Enzyme
Generic kinase
Protein kinase
Lipid kinase
Generic phosphatase
Protein phosphatase
Lipid phosphatase
Generic phospholipase
Generic protease
Metalloprotease
G-alpha
RAS - superfamily
G beta/gamma
Regulators (GDI, GAP, GEF)
Generic channel
Ligand-gated channel
Voltage-gated channel
Transporter
Normal process
Pathological process
Positive effect
Negative effect
Unspecified effect
Technical link
Disrupts in disease
Emerges in disease
Enhances in disease
Weakens in disease
Organsim specific interaction

Generic binding protein
Receptor ligand
Cell membrane glycoprotein
Transcription factor
DNA
RNA
Compound
Inorganic ion
Predicted metabolite or user's structure
Reaction
Generic receptor
GPCR
Receptors with enzyme activity
Mitochondria
EPR
Golgi
Nucleus
Lysosome
Peroxisome
Cytoplasm
Extracellular

Normal process
Pathological process
Binding
Cleavage
Covalent modifications
Phosphorylation
Dephosphorylation
Transformation
Transport
Catalysis
Transcription regulation
MicroRNA binding
Competition
Influence on expression
Unspecified interactions
Pharmacological effect
Toxic effect
Group relation
Complex subunit
Similarity reaction
A complex or a group
Organism specific object

Methionine metabolism


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Methionine metabolism

Methionine metabolism.

The first step in (L)-Methionine metabolism, the synthesis ofS-Adenosyl-(L)-methionine, is catalyzed by the Methionine adenosyltransferase I,alpha ( MAT1A ) [1], [2], [3] and Methionineadenosyltransferase II, alpha ( MAT2A ) [4], [2], [5], [3], [6].

S-Adenosyl-(L)-methionine (AdoMet) is the primary methyl group donor invirtually all mammalian systems. DNA (cytosine-5-)-methyltransferase 1 ( D nmt 1 )[7], [8], DNA (cytosine-5-)-methyltransferase 3 alpha (DNMT3A ) [9] and DNA (cytosine-5-)-methyltransferase 3 beta (DNMT3B ) [9] naturally catalyze the transfer of the activated methylgroup from AdoMet to C5 atom of DNA cytosine with formation ofS-Adenosyl-(L)-homocysteine ( AdoHcy ).

S-adenosylhomocysteine hydrolase ( SAHH ) [10], [11],[12], S-adenosylhomocysteine hydrolase-like 1 ( SAHH2 ) [13] and S-Adenosylhomocysteine hydrolase-like 2 ( SAHH3 ) [13]catalyze the hydrolysis of AdoHcy to adenosine and (L)-Homocysteine. In turn,Cystathionine beta-synthase ( CBS ) catalyzes the condensation of(L)-Serine and (L)-Homocysteine to form (L)-Cystathionine [14], [15]. Cystathionase (cystathionine gamma-lyase) ( CTH )catalyzes the second step in the reverse trans-sulfuration pathway (the cleavage of the(L)-Cystathionine C-gamma-S bond) yielding (L)-Cysteine, 2-Oxobutanoicacid, and ammonia [16].

(L)-Methionine, as another amino acid involved in protein biosynthesis, thatforms aminoacyl-tRNA conjugated with corresponding tRNA by Methionyl-tRNA synthetase (MARS) [17], [18]. Mitochondrial (L)-Methionine*(tRNA)then undergoes formylation to N-Formyl-(L)-methionine*(tRNA) by Mitochondrialmethionyl-tRNA formyltransferase ( FMT) [19].