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Catalytic Site Atlas

CSA LITERATURE entry for 1dhf

E.C. namedihydrofolate reductase
SpeciesHomo sapiens (Human)
E.C. Number (IntEnz)
CSA Homologues of 1dhfThere are 145 Homologs
CSA Entries With UniProtID P00374
CSA Entries With EC Number
PDBe Entry 1dhf
PDBSum Entry 1dhf
MACiE Entry 1dhf

Literature Report

IntroductionDihydrofolate reductase catalyses the reduction of 7,8-dihydrofolate (DHF) to 5,6,7,8-tetrahydrofolate (THF) by stereospecific hydride transfer from a NADPH cofactor to teh C6 atom of the pterin ring with concomitant protonation at N(5). DHFR plays a central role cell maintenance of THF reserves, which are essential for purine and thimidylate synthesis and hence for cell growth and proliferation. As DHFR is the sole source of THF, the enzyme is the Achilles heel of rapidly proliferating cells and, therefore, has been a major focus in the development of anticancer and antibacterial reagents.
MechansimThe structure of the human catalytic site differs from that of E Coli, and so the residues implicated in catalysis differ between the two organisms. Kinetics studies show the human enzyme utilises the protonated form of DHF where as the E. Coli enzyme catalyses simultaneous protonation and hydride transfer.
The first step of the reaction is a tautomerisation of the dihydrofolate substrate from the keto to enol form. The second step is a stereospecific hydride transfer from the NADPH cofactor to the C(5) of dihydrofolate. This step requires a general acid to donate a proton to N(5) in E. Coli, but no analogous residue exists in the human enzyme. A proton is abstracted from the enol oxygen during hydride transfer in a second tautomerisation to regenerate the keto form. The overall product is 5,6,7,8 tetrahydrofolate (THF).

Catalytic Sites for 1dhf

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
GluA3031macie:sideChain The residue is thought to position the dihydrofolate substrate for optimum reactivity with the hydride donor NADPH.
LeuA2223macie:sideChainThe non polar side chain disrupts the hydrogen bond between the substrate and Glu30 sufficiently to prevent the formation of an overly stable intermediate while also allowing Glu30 to hold the substrate in the correct orientation within the active site.

Literature References

Park H
Mechanistic studies of R67 dihydrofolate reductase. Effects of pH and an H62C mutation.
J Biol Chem 1997 272 2252-2258
PubMed: 8999931
Noda M.
Expression cloning of tumor suppressor genes: a guide for optimists.
Mol Carcinog 1990 3 251-253
PubMed: 2244959