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Structures of three inhibitor complexes provide insight into the reaction mechanism of the human methylenetetrahydrofolate dehydrogenase/cyclohydrolase.
Biochemistry. 2000 May 30; 39(21):6325-35.B

Abstract

Enzymes involved in tetrahydrofolate metabolism are of particular pharmaceutical interest, as their function is crucial for amino acid and DNA biosynthesis. The crystal structure of the human cytosolic methylenetetrahydrofolate dehydrogenase/cyclohydrolase (DC301) domain of a trifunctional enzyme has been determined previously with a bound NADP cofactor. While the substrate binding site was identified to be localized in a deep and rather hydrophobic cleft at the interface between two protein domains, the unambiguous assignment of catalytic residues was not possible. We succeeded in determining the crystal structures of three ternary DC301/NADP/inhibitor complexes. Investigation of these structures followed by site-directed mutagenesis studies allowed identification of the amino acids involved in catalysis by both enzyme activities. The inhibitors bind close to Lys56 and Tyr52, residues of a strictly conserved motif for active sites in dehydrogenases. While Lys56 is in a good position for chemical interaction with the substrate analogue, Tyr52 was found stacking against the inhibitors' aromatic rings and hence seems to be more important for proper positioning of the ligand than for catalysis. Also, Ser49 and/or Cys147 were found to possibly act as an activator for water in the cyclohydrolase step. These and the other residues (Gln100 and Asp125), with which contacts are made, are strictly conserved in THF dehydrogenases. On the basis of structural and mutagenesis data, we propose a reaction mechanism for both activities, the dehydrogenase and the cyclohydrolase.

Authors+Show Affiliations

Biotechnology Research Institute, National Research Council of Canada, Montreal Joint Centre for Structural Biology, Montreal, Quebec H4P 2R2 Canada.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

10828945

Citation

Schmidt, A, et al. "Structures of Three Inhibitor Complexes Provide Insight Into the Reaction Mechanism of the Human Methylenetetrahydrofolate Dehydrogenase/cyclohydrolase." Biochemistry, vol. 39, no. 21, 2000, pp. 6325-35.
Schmidt A, Wu H, MacKenzie RE, et al. Structures of three inhibitor complexes provide insight into the reaction mechanism of the human methylenetetrahydrofolate dehydrogenase/cyclohydrolase. Biochemistry. 2000;39(21):6325-35.
Schmidt, A., Wu, H., MacKenzie, R. E., Chen, V. J., Bewly, J. R., Ray, J. E., Toth, J. E., & Cygler, M. (2000). Structures of three inhibitor complexes provide insight into the reaction mechanism of the human methylenetetrahydrofolate dehydrogenase/cyclohydrolase. Biochemistry, 39(21), 6325-35.
Schmidt A, et al. Structures of Three Inhibitor Complexes Provide Insight Into the Reaction Mechanism of the Human Methylenetetrahydrofolate Dehydrogenase/cyclohydrolase. Biochemistry. 2000 May 30;39(21):6325-35. PubMed PMID: 10828945.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Structures of three inhibitor complexes provide insight into the reaction mechanism of the human methylenetetrahydrofolate dehydrogenase/cyclohydrolase. AU - Schmidt,A, AU - Wu,H, AU - MacKenzie,R E, AU - Chen,V J, AU - Bewly,J R, AU - Ray,J E, AU - Toth,J E, AU - Cygler,M, PY - 2000/6/1/pubmed PY - 2000/7/15/medline PY - 2000/6/1/entrez SP - 6325 EP - 35 JF - Biochemistry JO - Biochemistry VL - 39 IS - 21 N2 - Enzymes involved in tetrahydrofolate metabolism are of particular pharmaceutical interest, as their function is crucial for amino acid and DNA biosynthesis. The crystal structure of the human cytosolic methylenetetrahydrofolate dehydrogenase/cyclohydrolase (DC301) domain of a trifunctional enzyme has been determined previously with a bound NADP cofactor. While the substrate binding site was identified to be localized in a deep and rather hydrophobic cleft at the interface between two protein domains, the unambiguous assignment of catalytic residues was not possible. We succeeded in determining the crystal structures of three ternary DC301/NADP/inhibitor complexes. Investigation of these structures followed by site-directed mutagenesis studies allowed identification of the amino acids involved in catalysis by both enzyme activities. The inhibitors bind close to Lys56 and Tyr52, residues of a strictly conserved motif for active sites in dehydrogenases. While Lys56 is in a good position for chemical interaction with the substrate analogue, Tyr52 was found stacking against the inhibitors' aromatic rings and hence seems to be more important for proper positioning of the ligand than for catalysis. Also, Ser49 and/or Cys147 were found to possibly act as an activator for water in the cyclohydrolase step. These and the other residues (Gln100 and Asp125), with which contacts are made, are strictly conserved in THF dehydrogenases. On the basis of structural and mutagenesis data, we propose a reaction mechanism for both activities, the dehydrogenase and the cyclohydrolase. SN - 0006-2960 UR - https://www.unboundmedicine.com/medline/citation/10828945/Structures_of_three_inhibitor_complexes_provide_insight_into_the_reaction_mechanism_of_the_human_methylenetetrahydrofolate_dehydrogenase/cyclohydrolase_ L2 - https://doi.org/10.1021/bi992734y DB - PRIME DP - Unbound Medicine ER -