Enzymes
| UniProtKB help_outline | 3,178 proteins |
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- Name help_outline 5,10-methenyl-5,6,7,8-tetrahydromethanopterin Identifier CHEBI:58337 Charge -2 Formula C31H41N6O16P InChIKeyhelp_outline RANKJVUGLXUXOL-CAFBYHECSA-L SMILEShelp_outline [H][C@]12[C@H](C)Nc3nc(N)[nH]c(=O)c3[N+]1=CN([C@@H]2C)c1ccc(C[C@H](O)[C@H](O)[C@H](O)CO[C@H]2O[C@H](COP([O-])(=O)O[C@@H](CCC([O-])=O)C([O-])=O)[C@@H](O)[C@H]2O)cc1 2D coordinates Mol file for the small molecule Search links Involved in 5 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline H2O Identifier CHEBI:15377 (Beilstein: 3587155; CAS: 7732-18-5) help_outline Charge 0 Formula H2O InChIKeyhelp_outline XLYOFNOQVPJJNP-UHFFFAOYSA-N SMILEShelp_outline [H]O[H] 2D coordinates Mol file for the small molecule Search links Involved in 6,204 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline H+ Identifier CHEBI:15378 Charge 1 Formula H InChIKeyhelp_outline GPRLSGONYQIRFK-UHFFFAOYSA-N SMILEShelp_outline [H+] 2D coordinates Mol file for the small molecule Search links Involved in 9,431 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline N5-formyl-5,6,7,8-tetrahydromethanopterin Identifier CHEBI:58018 Charge -3 Formula C31H42N6O17P InChIKeyhelp_outline RMPHWTMYCVTPKB-QZQIFXBMSA-K SMILEShelp_outline [H][C@](C)(Nc1ccc(C[C@]([H])(O)[C@]([H])(O)[C@]([H])(O)CO[C@H]2O[C@H](COP([O-])(=O)O[C@@]([H])(CCC([O-])=O)C([O-])=O)[C@@H](O)[C@H]2O)cc1)C1N(C=O)c2c(N[C@@]1([H])C)nc(N)[nH]c2=O 2D coordinates Mol file for the small molecule Search links Involved in 2 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
Cross-references
| RHEA:19053 | RHEA:19054 | RHEA:19055 | RHEA:19056 | |
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| Reaction direction help_outline | undefined | left-to-right | right-to-left | bidirectional |
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Publications
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The crystal structure of methenyltetrahydromethanopterin cyclohydrolase from the hyperthermophilic archaeon Methanopyrus kandleri.
Grabarse W., Vaupel M., Vorholt J.A., Shima S., Thauer R.K., Wittershagen A., Bourenkov G., Bartunik H.D., Ermler U.
<h4>Background</h4>The reduction of carbon dioxide to methane in methanogenic archaea involves the tetrahydrofolate analogue tetrahydromethanopterin (H(4)MPT) as a C(1) unit carrier. In the third step of this reaction sequence, N(5)-formyl-H(4)MPT is converted to methenyl-H(4)MPT(+) by the enzyme ... >> More
<h4>Background</h4>The reduction of carbon dioxide to methane in methanogenic archaea involves the tetrahydrofolate analogue tetrahydromethanopterin (H(4)MPT) as a C(1) unit carrier. In the third step of this reaction sequence, N(5)-formyl-H(4)MPT is converted to methenyl-H(4)MPT(+) by the enzyme methenyltetrahydromethanopterin cyclohydrolase. The cyclohydrolase from the hyperthermophilic archaeon Methanopyrus kandleri (Mch) is extremely thermostable and adapted to a high intracellular concentration of lyotropic salts.<h4>Results</h4>Mch was crystallized and its structure solved at 2.0 A resolution using a combination of the single isomorphous replacement (SIR) and multiple anomalous dispersion (MAD) techniques. The structure of the homotrimeric enzyme reveals a new alpha/beta fold that is composed of two domains forming a large sequence-conserved pocket between them. Two phosphate ions were found in and adjacent to this pocket, respectively; the latter is displaced by the phosphate moiety of the substrate formyl-H(4)MPT according to a hypothetical model of the substrate binding.<h4>Conclusions</h4>Although the exact position of the substrate is not yet known, the residues lining the active site of Mch could be tentatively assigned. Comparison of Mch with the tetrahydrofolate-specific cyclohydrolase/dehydrogenase reveals similarities in domain arrangement and in some active-site residues, whereas the fold appears to be different. The adaptation of Mch to high salt concentrations and high temperatures is reflected by the excess of acidic residues at the trimer surface and by the higher oligomerization state of Mch compared with its mesophtic counterparts. << Less
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Structure and catalytic mechanism of N(5),N(10)-methenyl-tetrahydromethanopterin cyclohydrolase.
Upadhyay V., Demmer U., Warkentin E., Moll J., Shima S., Ermler U.
Methenyltetrahydromethanopterin (methenyl-H(4)MPT(+)) cyclohydrolase (Mch) catalyzes the interconversion of methenyl-H(4)MPT(+) and formyl-H(4)MPT in the one-carbon energy metabolism of methanogenic, methanotrophic, and sulfate-reducing archaea and of methylotrophic bacteria. To understand the cat ... >> More
Methenyltetrahydromethanopterin (methenyl-H(4)MPT(+)) cyclohydrolase (Mch) catalyzes the interconversion of methenyl-H(4)MPT(+) and formyl-H(4)MPT in the one-carbon energy metabolism of methanogenic, methanotrophic, and sulfate-reducing archaea and of methylotrophic bacteria. To understand the catalytic mechanism of this reaction, we kinetically characterized site-specific variants of Mch from Archaeoglobus fulgidus (aMch) and determined the X-ray structures of the substrate-free aMch(E186Q), the aMch:H(4)MPT complex, and the aMch(E186Q):formyl-H(4)MPT complex. (Formyl-)H(4)MPT is embedded inside a largely preformed, interdomain pocket of the homotrimeric enzyme with the pterin and benzyl rings being oriented nearly perpendicular to each other. The active site is primarily built up by the segment 93:95, Arg183 and Glu186 that either interact with the catalytic water attacking methenyl-H(4)MPT(+) or with the formyl oxygen of formyl-H(4)MPT. The catalytic function of the strictly conserved Arg183 and Glu186 was substantiated by the low enzymatic activities of the E186A, E186D, E186N, E186Q, R183A, R183Q, R183E, R183K, and R183E-E186Q variants. Glu186 most likely acts as a general base. Arg183 decisively influences the pK(a) value of Glu186 and the proposed catalytic water mainly by its positive charge. In addition, Glu186 appears to be also responsible for product specificity by donating a proton to the directly neighbored N(10) tertiary amine of H(4)MPT. Thus, N(10) becomes a better leaving group than N(5) which implies the generation of N(5)-formyl-H(4)MPT. For comparison, methenyltetrahydrofolate (H(4)F) cyclohydrolase produces N(10)-formyl-H(4)F in an analogous reaction. An enzymatic mechanism of Mch is postulated and compared with that of other cyclohydrolases. << Less
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Methenyl-tetrahydromethanopterin cyclohydrolase in cell extracts of Methanobacterium.
Donnelly M.I., Escalante-Semerena J.C., Rinehart K.L. Jr., Wolfe R.S.
Cell extracts of Methanobacterium thermoautotrophicum possess a methenyl-tetrahydromethanopterin (methenyl-H4MPT) cyclohydrolase. The enzyme catalyzes the hydrolysis of methenyl-H4MPT to formyltetrahydromethanopterin (formyl-H4MPT). The reaction is reversible and both the rate and extent of the re ... >> More
Cell extracts of Methanobacterium thermoautotrophicum possess a methenyl-tetrahydromethanopterin (methenyl-H4MPT) cyclohydrolase. The enzyme catalyzes the hydrolysis of methenyl-H4MPT to formyltetrahydromethanopterin (formyl-H4MPT). The reaction is reversible and both the rate and extent of the reaction depend on the pH and the buffer used. Similarly, the nonenzymatic hydrolysis of methenyl-H4MPT is highly dependent on pH and buffer. An active derivative of methenyl-H4MPT was obtained in 94% yield by reacting H4MPT with formic acid in the presence of excess acetic acid under anoxic conditions at 80 degrees C for 3 h. H NMR spectroscopy and fast atom bombardment mass spectrometry revealed the product to be a derivative of methenyl-H4MPT which had lost the alpha-hydroxyglutarylphosphate unit. In spite of this loss, this derivative served both as a substrate for methanogenesis and for the cyclohydrolase. Comparison of the properties of the products of the enzymatic and nonenzymatic hydrolyses indicates that the enzymatic reaction yields N5-formyl-H4MPT whereas the nonenzymatic reaction yields N10-formyl-H4MPT. << Less