Mammalian dihydrofolate reductases (DHFRs) catalyze the reduction of folate more efficiently than the equivalent bacterial enzymes do, despite typically having similar efficiencies for the reduction of their natural substrate, dihydrofolate. In contrast, we show here that DHFR from the hyperthermophilic bacterium Thermotoga maritima can catalyze reduction of folate to tetrahydrofolate with an efficiency similar to that of reduction of dihydrofolate under saturating conditions. Nuclear magnetic resonance and mass spectrometry experiments showed no evidence of the production of free dihydrofolate during either the EcDHFR- or TmDHFR-catalyzed reductions of folate, suggesting that both enzymes perform the two reduction steps without release of the partially reduced substrate. Our results imply that the reaction proceeds more efficiently in TmDHFR than in EcDHFR because the more open active site of TmDHFR facilitates protonation of folate. Because T. maritima lives under extreme conditions where tetrahydrofolate is particularly prone to oxidation, this ability to salvage folate may impart an advantage to the bacterium by minimizing the squandering of a valuable cofactor.

• MeSH
• bakteriální proteiny chemie   genetika   metabolismus   MeSH
• dihydrofolátreduktasa chemie   genetika   metabolismus   MeSH
• druhová specificita MeSH
• Escherichia coli chemie   enzymologie   genetika   MeSH
• exprese genu MeSH
• katalytická doména MeSH
• kinetika MeSH
• koncentrace vodíkových iontů MeSH
• kyselina listová chemie   metabolismus   MeSH
• NADP chemie   metabolismus   MeSH
• oxidace-redukce MeSH
• protony * MeSH
• sbalování proteinů MeSH
• sekundární struktura proteinů MeSH
• teplota MeSH
• termodynamika MeSH
• tetrahydrofoláty chemie   metabolismus   MeSH
• Thermotoga maritima chemie   enzymologie   genetika   MeSH
• Publikační typ
• časopisecké články MeSH