Enzymes
UniProtKB help_outline | 903 proteins |
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Reaction participants Show >> << Hide
- Name help_outline CMP-N-acetyl-β-neuraminate Identifier CHEBI:57812 (Beilstein: 5899715) help_outline Charge -2 Formula C20H29N4O16P InChIKeyhelp_outline TXCIAUNLDRJGJZ-BILDWYJOSA-L SMILEShelp_outline [H][C@]1(O[C@](C[C@H](O)[C@H]1NC(C)=O)(OP([O-])(=O)OC[C@H]1O[C@H]([C@H](O)[C@@H]1O)n1ccc(N)nc1=O)C([O-])=O)[C@H](O)[C@H](O)CO 2D coordinates Mol file for the small molecule Search links Involved in 72 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
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Namehelp_outline
Fe(II)-[cytochrome b5]
Identifier
RHEA-COMP:10438
Reactive part
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- Name help_outline Fe2+ Identifier CHEBI:29033 (CAS: 15438-31-0) help_outline Charge 2 Formula Fe InChIKeyhelp_outline CWYNVVGOOAEACU-UHFFFAOYSA-N SMILEShelp_outline [Fe++] 2D coordinates Mol file for the small molecule Search links Involved in 250 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 9,176 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline O2 Identifier CHEBI:15379 (CAS: 7782-44-7) help_outline Charge 0 Formula O2 InChIKeyhelp_outline MYMOFIZGZYHOMD-UHFFFAOYSA-N SMILEShelp_outline O=O 2D coordinates Mol file for the small molecule Search links Involved in 2,648 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline CMP-N-glycoloyl-β-neuraminate Identifier CHEBI:58376 Charge -2 Formula C20H29N4O17P InChIKeyhelp_outline HOEWKBQADMRCLO-UIUGZIMDSA-L SMILEShelp_outline [H][C@]1(O[C@](C[C@H](O)[C@H]1NC(=O)CO)(OP([O-])(=O)OC[C@H]1O[C@H]([C@H](O)[C@@H]1O)n1ccc(N)nc1=O)C([O-])=O)[C@H](O)[C@H](O)CO 2D coordinates Mol file for the small molecule Search links Involved in 1 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
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Namehelp_outline
Fe(III)-[cytochrome b5]
Identifier
RHEA-COMP:10439
Reactive part
help_outline
- Name help_outline Fe3+ Identifier CHEBI:29034 (CAS: 20074-52-6) help_outline Charge 3 Formula Fe InChIKeyhelp_outline VTLYFUHAOXGGBS-UHFFFAOYSA-N SMILEShelp_outline [Fe+3] 2D coordinates Mol file for the small molecule Search links Involved in 234 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 6,048 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
Cross-references
RHEA:16145 | RHEA:16146 | RHEA:16147 | RHEA:16148 | |
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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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Cloning and expression of a membrane-bound CMP-N-acetylneuraminic acid hydroxylase from the starfish Asterias rubens.
Martensen I., Schauer R., Shaw L.
The sialic acid N-glycolylneuraminic acid (Neu5Gc) is synthesized by the action of CMP-Neu5Ac hydroxylase. The enzyme from various mammals has been purified, characterized and sequenced by cDNA cloning. Although functional sequence motifs can be postulated from comparisons with several enzymes, no ... >> More
The sialic acid N-glycolylneuraminic acid (Neu5Gc) is synthesized by the action of CMP-Neu5Ac hydroxylase. The enzyme from various mammals has been purified, characterized and sequenced by cDNA cloning. Although functional sequence motifs can be postulated from comparisons with several enzymes, no global homologies to any other proteins have been found. The unusual characteristics of this hydroxylase raise questions about its evolution. As echinoderms are phylogenetically the oldest organisms possessing Neu5Gc, they represent a starting point for investigations on the origin of this enzyme. Despite many similarities with its mammalian counterpart, CMP-Neu5Ac hydroxylase from the starfish A. rubens exhibits fundamental differences, most notably its association with a membrane and a requirement for high ionic strength. In order to shed light on the structural basis for these differences, the primary structure of CMP-Neu5Ac hydroxylase from A. rubens has been determined by PCR and cDNA-cloning techniques, using initial sequence information from the mouse enzyme. The complete assembled cDNA contained an ORF coding for a protein of 653 amino acids with a molecular mass of 75 kDa. The deduced amino-acid sequence exhibited a high degree of homology with the mammalian enzyme, although the C-terminus was some 60 residues longer. This extension consists of a terminal hydrophobic region, which may mediate membrane-binding, and a preceding hydrophilic sequence which probably serves as a hinge or linker. The identity of the ORF was confirmed by expression of active CMP-Neu5Ac hydroxylase in E. coli at low temperatures. << Less
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Reduction of CMP-N-acetylneuraminic acid hydroxylase activity in engineered Chinese hamster ovary cells using an antisense-RNA strategy.
Chenu S., Gregoire A., Malykh Y., Visvikis A., Monaco L., Shaw L., Schauer R., Marc A., Goergen J.-L.
Rodent cells, widely used for the industrial production of recombinant human glycoproteins, possess CMP-N-acetylneuraminic acid hydroxylase (CMP-Neu5Ac hydroxylase; EC 1.14.13.45) which is the key enzyme in the formation of the sialic acid, N-glycolylneuraminic acid (Neu5Gc). This enzyme is not ex ... >> More
Rodent cells, widely used for the industrial production of recombinant human glycoproteins, possess CMP-N-acetylneuraminic acid hydroxylase (CMP-Neu5Ac hydroxylase; EC 1.14.13.45) which is the key enzyme in the formation of the sialic acid, N-glycolylneuraminic acid (Neu5Gc). This enzyme is not expressed in an active form in man and evidence suggests that the presence of Neu5Gc in recombinant therapeutic glycoproteins may elicit an immune response. The aim of this work was, therefore, to reduce CMP-Neu5Ac hydroxylase activity in a Chinese Hamster Ovary (CHO) cell line, and thus the Neu5Gc content of the resulting glycoconjugates, using a rational antisense RNA approach. For this purpose, the cDNA of the hamster hydroxylase was partially cloned and sequenced. Based on the sequence of the mouse and hamster cDNAs, optimal antisense RNA fragments were selected from preliminary in vitro translation tests. Compared to the parental cell line, the new strain (CHO-AsUH2), which was transfected with a 199-bp antisense fragment derived from the mouse CMP-Neu5Ac hydroxylase cDNA, showed an 80% reduction in hydroxylase activity. An analysis of the sialic acids present in the cells' own glycoconjugates revealed a decrease in the percentage of Neu5Gc residues from 4% in the parental cells to less than 1% in the CHO-AsUH2 cell line. << Less
Biochim. Biophys. Acta 1622:133-144(2003) [PubMed] [EuropePMC]
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Metabolism of vertebrate amino sugars with N-glycolyl groups: elucidating the intracellular fate of the non-human sialic acid N-glycolylneuraminic acid.
Bergfeld A.K., Pearce O.M., Diaz S.L., Pham T., Varki A.
The two major mammalian sialic acids are N-acetylneuraminic acid and N-glycolylneuraminic acid (Neu5Gc). The only known biosynthetic pathway generating Neu5Gc is the conversion of CMP-N-acetylneuraminic acid into CMP-Neu5Gc, which is catalyzed by the CMP-Neu5Ac hydroxylase enzyme. Given the irreve ... >> More
The two major mammalian sialic acids are N-acetylneuraminic acid and N-glycolylneuraminic acid (Neu5Gc). The only known biosynthetic pathway generating Neu5Gc is the conversion of CMP-N-acetylneuraminic acid into CMP-Neu5Gc, which is catalyzed by the CMP-Neu5Ac hydroxylase enzyme. Given the irreversible nature of this reaction, there must be pathways for elimination or degradation of Neu5Gc, which would allow animal cells to adjust Neu5Gc levels to their needs. Although humans are incapable of synthesizing Neu5Gc due to an inactivated CMAH gene, exogenous Neu5Gc from dietary sources can be metabolically incorporated into tissues in the face of an anti-Neu5Gc antibody response. However, the metabolic turnover of Neu5Gc, which apparently prevents human cells from continued accumulation of this immunoreactive sialic acid, has not yet been elucidated. In this study, we show that pre-loaded Neu5Gc is eliminated from human cells over time, and we propose a conceivable Neu5Gc-degrading pathway based on the well studied metabolism of N-acetylhexosamines. We demonstrate that murine tissue cytosolic extracts harbor the enzymatic machinery to sequentially convert Neu5Gc into N-glycolylmannosamine, N-glycolylglucosamine, and N-glycolylglucosamine 6-phosphate, whereupon irreversible de-N-glycolylation of the latter results in the ubiquitous metabolites glycolate and glucosamine 6-phosphate. We substantiate this finding by demonstrating activity of recombinant human enzymes in vitro and by studying the fate of radiolabeled pathway intermediates in cultured human cells, suggesting that this pathway likely occurs in vivo. Finally, we demonstrate that the proposed degradative pathway is partially reversible, showing that N-glycolylmannosamine and N-glycolylglucosamine (but not glycolate) can serve as precursors for biosynthesis of endogenous Neu5Gc. << Less
J. Biol. Chem. 287:28865-28881(2012) [PubMed] [EuropePMC]
This publication is cited by 2 other entries.