Polymer: (6R)-5,10-methylenetetrahydrofolyl-(γ-L-Glu)(n)
Tetrahydrofolate synthases (EC 6.3.2.17) catalyze the ATP-dependent addition of glutamate moieties to folate and folate derivatives via γ peptide linkage. The reaction is RHEA:51912. RHEA:51912 is a polymerization reaction that uses the underlying ChEBI polymer CHEBI:136572 ((6R)-5,10-methylenetetrahydrofolyl-(γ-L-Glu)(n)) with different polymerization indices (PIs):
| Rhea polymer identifier | Rhea polymer name | PI | Underlying ChEBI polymer |
|---|---|---|---|
| RHEA-COMP:13257 | (6R)-5,10-methylenetetrahydrofolyl-(γ-L-Glu)n | n | CHEBI:136572 |
| RHEA-COMP:13258 | (6R)-5,10-methylenetetrahydrofolyl-(γ-L-Glu)n+1 | n+1 | CHEBI:136572 |
Alternatively, dimethylglycine dehydrogenases (EC 1.5.8.4) catalyze the oxidative demethylation of N,N-dimethylglycine to sarcosine and use a noncovalently bound 5,6,7,8-tetrahydrofolate coenzyme as the methyl acceptor to form a 5,10-methylenetetrahydropteroyl derivative.
The corresponding reaction is RHEA:52856. RHEA:52856 is a reaction involving the modification of the (6S)-5,6,7,8-tetrahydrofolyl constant part of RHEA-COMP:14738 polymer, to form a (6R)-5,10-methylenetetrahydrofolyl derivative (RHEA-COMP:13257).
| Rhea polymer identifier | Rhea polymer name | PI | Underlying ChEBI polymer |
|---|---|---|---|
| RHEA-COMP:14738 | (6S)-5,6,7,8-tetrahydrofolyl-(γ-L-Glu)n | n | CHEBI:141005 |
| RHEA-COMP:13257 | (6R)-5,10-methylenetetrahydrofolyl-(γ-L-Glu)n | n | CHEBI:136572 |
We can see in this second reaction that the Rhea polymers are identical to the ChEBI underlying polymers. However, to be able to balance the reaction and to be able to link reactions by their participants, we use Rhea polymers in RHEA:52856.
