A synthetic antibacterial drug - Uppsala University
1
Trimethoprim: A bacterial specific dihydrofolate reductase inhibitor used in the treatment of urinary tract infections Valencia, I. Proteins and Drugs, Spring 2011 References 1. Roth B, Falco E, Hitchings G, Bushby S (1962). 5-benzyl-2, 4-diaminopyrimidines as Antibacterial Agents.I.Synthesis and antibacterial activity in vivo. J. Med. Chem. 5:1103-1123. 2. Grüneberg R, Path M, Kolbe R et al (1969). Trimethoprim in the treatment of urinary infections in hospital. British Medical Journal.33:545-547. 3. DrugBank. Trimethoprim –Accesion number DB00440 (APRD00103). 4. Schnell JR, Dyson HJ, Wright PE (2004). Structure, dynamics, and catalytic function of dihydrofolate reductase. Annual Review of Biophysics and Biomolecular Structure 33: 119–40 5. Garret R and Grisham C. Biochemistry. Brooks/Cole CENGAGE Learning. Fourth edition. Boston, MA, USA, 2010. 6. Feeney J, Birdsall B, Kivalevskaya N et al. (2011). NMR structures of Apo L.casei Dihydrofolate reductase and its complexes with Trimethoprim and NADPH. Biochemistry. 50:3609-3620. 7. Birdsall B, Roberts G, Feeney J et al. (1983). Trimethoprim binding to bacterial and mammalian dihydrofolate reductase. Biochemistry. 22:5597-5604. 8. S. Bushby. Trimethoprim-sulfumethoxazole, Microbiological, Pharmacological and Clinical Considerations, Ed. by M. Finland and E.H. Kass, pp. l0-30 (1973). Trimethoprim acts as an inhibitor of DHFR in the conversion of 7, 8- dihydrofolate (FH2) to 5, 6, 7, 8- tetrahydrofolate (FH4). Tetrahy- drofolic acid is an essential pre- cursor in bacterial de novo syn- thesis of purines and thymidine. Since bacterial source of FH2 is limited to its de novo synthesis, the inhibition of DHFR results in DNA replication arrest and even- tually, cellular death [4]. A synthetic antibacterial drug Trimethoprim [2, 4-diamino-5-(3, 4, 5-trimethoxybenzyl) pyrimidine] was developed by Hitchings G et al in 1862 [1]. It is a dihydrofolate reductase (DHFR) inhibitor mainly used as a folic acid antagonist and anti-infecting agent. Its selective bactericidal activity consists on blocking folate synthesis in the bacterial thymidine synthesis pathway, therefore disrupting DNA replication process [2]. It is administered orally and 10-20% is metabolized in the liver. Trimethoprim (TMP) is active against most strains of aerobic gram-positive and -negative microorgan- isms, such as Staphylococcus, Entobacter species, E.coli, K.pneumoniae and P.mirabilis [3]. Therefore, it is pre- scribed for treating urinary, intestinal and respiratory tract infections. Trimethoprim binds at least 3000 times more tightly to bac- terial than to mammalian DHFR. Structural variations in DHFR between species cause trimethoprim to adopt differ- ent conformations when bounded to prokaryotic or eukary- otic enzymes. The conformations of bounded trimethoprim differ by approximately 25° in both torsion angles, influenc- ing significantly in structural differences that arise between them [7]. SMX increases antibacterial efficiency Trimethoprim [3] The cooperative binding of NADPH plays an important role in both the enzyme ca- talysis and inhibition. Tri- methoprim binds to bacterial DHFR 135 times more tightly in the presence if NADPH [6]. Mechanism of Action DHFR and its complexes [6] Thymidylate synthesis [5]. Studies have also attrib- uted this specificity to a decrease of positive NADPH cooperative bind- ing in mammalian DHFR complex. In contrast, con- tributions from the A-B loop and helix B refolding of bacterial DHFR favors positive binding coopera- tivity in the DHFR-TMP- NADPH complex [6]. Specificity in Bacterial DHFR TMP-NADPH complex bounded to (left) mammalian and (right) bacterial DHFR [3]. Comparison of the A-B loop structures in apo L. casei DHFR [6]. Co-trimoxazole is an anti- bacterial that combines tri- methoprim with sulfameth- oxazole (SMX), a dihydrop- teroate synthetase inhibitor, to create a sequential bio- synthetic blocking. The mini- mum inhibitory concentra- tions (MIC) of one compound may be reduced up to 10- or 20-fold when the other com- pound is present [8]. Conclusion Trimethoprim is a DHFR inhibitor used for treating urinary tract infections. Since bacteria are unable to uptake folic acid from vitamins, the inhibition of their de novo synthesis pathway disrupts cell growth mechanisms causing bacte- rial death. Structural differences between bacterial and mammalian DHFR and its binding complex with TMP- NADPH influence specificity of trimethoprim against bac- terial enzymes. It is usually prescribed in combination with a sulfonamide antibiotic known as sulfamethoxazole. Minimal inhibitory concentration TMP: SMX - 1:20 [8]
Transcript of A synthetic antibacterial drug - Uppsala University
Trimethoprim: A bacterial specific dihydrofolate reductase inhibitor used in the treatment of urinary tract infections
Valencia, I.Proteins and Drugs, Spring 2011
References1. Roth B, Falco E, Hitchings G, Bushby S (1962). 5-benzyl-2, 4-diaminopyrimidines as Antibacterial Agents.I.Synthesis and antibacterial activity in vivo. J. Med. Chem. 5:1103-1123.2. Grüneberg R, Path M, Kolbe R et al (1969). Trimethoprim in the treatment of urinary infections in hospital. British Medical Journal.33:545-547.3. DrugBank. Trimethoprim –Accesion number DB00440 (APRD00103).4. Schnell JR, Dyson HJ, Wright PE (2004). Structure, dynamics, and catalytic function of dihydrofolate reductase. Annual Review of Biophysics and Biomolecular Structure 33: 119–405. Garret R and Grisham C. Biochemistry. Brooks/Cole CENGAGE Learning. Fourth edition. Boston, MA, USA, 2010. 6. Feeney J, Birdsall B, Kivalevskaya N et al. (2011). NMR structures of Apo L.casei Dihydrofolate reductase and its complexes with Trimethoprim and NADPH. Biochemistry. 50:3609-3620.7. Birdsall B, Roberts G, Feeney J et al. (1983). Trimethoprim binding to bacterial and mammalian dihydrofolate reductase. Biochemistry. 22:5597-5604.8. S. Bushby. Trimethoprim-sulfumethoxazole, Microbiological, Pharmacological and Clinical Considerations, Ed. by M. Finland and E.H. Kass, pp. l0-30 (1973).
Trimethoprim acts as an inhibitor of DHFR in the conversion of 7, 8-dihydrofolate (FH2) to 5, 6, 7, 8-tetrahydrofolate (FH4). Tetrahy-drofolic acid is an essential pre-cursor in bacterial de novo syn-thesis of purines and thymidine. Since bacterial source of FH2 is limited to its de novo synthesis, the inhibition of DHFR results in DNA replication arrest and even-
tually, cellular death [4].
A synthetic antibacterial drug Trimethoprim [2, 4-diamino-5-(3, 4, 5-trimethoxybenzyl) pyrimidine] was developed by Hitchings G et al in 1862 [1]. It is a dihydrofolate reductase (DHFR) inhibitor mainly used as a folic acid antagonist and anti-infecting agent. Its selective bactericidal activity consists on blocking folate synthesis in the bacterial thymidine synthesis pathway, therefore disrupting DNA replication process [2]. It is administered orally and 10-20% is metabolized in the liver. Trimethoprim (TMP) is active against most strains of aerobic gram-positive and -negative microorgan-isms, such as Staphylococcus, Entobacter species, E.coli, K.pneumoniae and P.mirabilis [3]. Therefore, it is pre-
scribed for treating urinary, intestinal and respiratory tract infections.
Trimethoprim binds at least 3000 times more tightly to bac-terial than to mammalian DHFR. Structural variations in DHFR between species cause trimethoprim to adopt differ-ent conformations when bounded to prokaryotic or eukary-otic enzymes. The conformations of bounded trimethoprim differ by approximately 25° in both torsion angles, influenc-ing significantly in structural differences that arise between
them [7].
SMX increases antibacterial efficiency
Trimethoprim [3]
The cooperative binding of NADPH plays an important role in both the enzyme ca-talysis and inhibition. Tri-methoprim binds to bacterial DHFR 135 times more tightly in
the presence if NADPH [6].
Mechanism of Action
DHFR and its complexes [6]
Thymidylate synthesis [5].
Studies have also attrib-uted this specificity to a decrease of positive NADPH cooperative bind-ing in mammalian DHFR complex. In contrast, con-tributions from the A-B loop and helix B refolding of bacterial DHFR favors positive binding coopera-tivity in the DHFR-TMP-
NADPH complex [6].
Specificity in Bacterial DHFR
TMP-NADPH complex bounded to (left) mammalian and (right) bacterial DHFR [3].
Comparison of the A-B loop structures in apo L. casei DHFR
[6].
Co-trimoxazole is an anti-bacterial that combines tri-methoprim with sulfameth-oxazole (SMX), a dihydrop-teroate synthetase inhibitor, to create a sequential bio-synthetic blocking. The mini-mum inhibitory concentra-tions (MIC) of one compound may be reduced up to 10- or 20-fold when the other com-
pound is present [8].
ConclusionTrimethoprim is a DHFR inhibitor used for treating urinary tract infections. Since bacteria are unable to uptake folic acid from vitamins, the inhibition of their de novo synthesis pathway disrupts cell growth mechanisms causing bacte-rial death. Structural differences between bacterial and mammalian DHFR and its binding complex with TMP-NADPH influence specificity of trimethoprim against bac-terial enzymes. It is usually prescribed in combination with
a sulfonamide antibiotic known as sulfamethoxazole.
Minimal inhibitory concentration TMP: SMX - 1:20 [8]
