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- Name help_outline α-D-galactose Identifier CHEBI:28061 (CAS: 26566-61-0,3646-73-9,59-23-4) help_outline Charge 0 Formula C6H12O6 InChIKeyhelp_outline WQZGKKKJIJFFOK-PHYPRBDBSA-N SMILEShelp_outline OC[C@H]1O[C@H](O)[C@H](O)[C@@H](O)[C@H]1O 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
- Name help_outline β-D-galactose Identifier CHEBI:27667 (CAS: 7296-64-2) help_outline Charge 0 Formula C6H12O6 InChIKeyhelp_outline WQZGKKKJIJFFOK-FPRJBGLDSA-N SMILEShelp_outline OC[C@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@H]1O 2D coordinates Mol file for the small molecule Search links Involved in 6 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
Cross-references
| RHEA:28675 | RHEA:28676 | RHEA:28677 | RHEA:28678 | |
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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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Mutarotase from Penicillium notatum. I. Purification, assay, and general properties of the enzyme.
BENTLEY R., BHATE D.S.
J Biol Chem 235:1219-1224(1960) [PubMed] [EuropePMC]
This publication is cited by 1 other entry.
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Biological catalysis of mutarotation of glucose.
KEILIN D., HARTREE E.F.
Biochem J 50:341-348(1952) [PubMed] [EuropePMC]
This publication is cited by 1 other entry.
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A rotographic study of mutarotase.
LEVY G.B., COOK E.S.
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Molecular structure of human galactose mutarotase.
Thoden J.B., Timson D.J., Reece R.J., Holden H.M.
Galactose mutarotase catalyzes the conversion of beta-d-galactose to alpha-d-galactose during normal galactose metabolism. The enzyme has been isolated from bacteria, plants, and animals and is present in the cytoplasm of most cells. Here we report the x-ray crystallographic analysis of human gala ... >> More
Galactose mutarotase catalyzes the conversion of beta-d-galactose to alpha-d-galactose during normal galactose metabolism. The enzyme has been isolated from bacteria, plants, and animals and is present in the cytoplasm of most cells. Here we report the x-ray crystallographic analysis of human galactose mutarotase both in the apoform and complexed with its substrate, beta-d-galactose. The polypeptide chain folds into an intricate array of 29 beta-strands, 25 classical reverse turns, and 2 small alpha-helices. There are two cis-peptide bonds at Arg-78 and Pro-103. The sugar ligand sits in a shallow cleft and is surrounded by Asn-81, Arg-82, His-107, His-176, Asp-243, Gln-279, and Glu-307. Both the side chains of Glu-307 and His-176 are in the proper location to act as a catalytic base and a catalytic acid, respectively. These residues are absolutely conserved among galactose mutarotases. To date, x-ray models for three mutarotases have now been reported, namely that described here and those from Lactococcus lactis and Caenorhabditis elegans. The molecular architectures of these enzymes differ primarily in the loop regions connecting the first two beta-strands. In the human protein, there are six extra residues in the loop compared with the bacterial protein for an approximate longer length of 9 A. In the C. elegans protein, the first 17 residues are missing, thereby reducing the total number of beta-strands by one. << Less
J. Biol. Chem. 279:23431-23437(2004) [PubMed] [EuropePMC]
This publication is cited by 1 other entry.
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Galactose mutarotase: purification, characterization, and investigations of two important histidine residues.
Beebe J.A., Frey P.A.
Galactose mutarotase catalyzes the interconversion of alpha- and beta-anomers of aldoses and is a recently identified member of the gal operon of Escherichia coli and participant in the Leloir pathway [Bouffard et al. (1994) J. Mol. Biol. 244, 269-278]. We report the purification and characterizat ... >> More
Galactose mutarotase catalyzes the interconversion of alpha- and beta-anomers of aldoses and is a recently identified member of the gal operon of Escherichia coli and participant in the Leloir pathway [Bouffard et al. (1994) J. Mol. Biol. 244, 269-278]. We report the purification and characterization of this enzyme, as well as mechanistic studies involving chemical modification with diethylpyrocarbonate (DEPC) and site-directed mutagenesis demonstrating the significance of two conserved histidine residues. The enzyme lacks metal ions and oxidoreduction cofactors, and an extinction coefficient of (6.2 +/-0.4) x 10(4) M-1 cm-1 has been measured by quantitative amino acid analysis. The catalytic mechanism is likely concerted general acid/general base. Experiments involving modification with DEPC suggest that a histidine is essential and is protected by substrate. Furthermore, site-directed mutagenesis of two conserved histidines was performed, and characterization of these mutants (His104Gln and His175Asn) illustrates the significance of these residues. Kinetic analysis of H104Q demonstrates an increase in KM of about 600-fold, a decrease in kcat of approximately 7-fold, and a 4000-fold decrease in kcat/KM as compared to the wild-type enzyme. The activity of His175Asn mutant, on the other hand, was too low to be measured accurately, and His 175 remains a candidate for the general base. These mutants were also subjected to DEPC modification, and results are consistent with the presence of two important histidines positioned closely together in the active site. << Less
Biochemistry 37:14989-14997(1998) [PubMed] [EuropePMC]
This publication is cited by 3 other entries.
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The catalytic mechanism of galactose mutarotase.
Thoden J.B., Kim J., Raushel F.M., Holden H.M.
Galactose mutarotase catalyzes the first step in normal galactose metabolism by catalyzing the conversion of beta-D-galactose to alpha-D-galactose. The structure of the enzyme from Lactococcus lactis was recently solved in this laboratory and shown to be topologically similar to domain 5 of beta-g ... >> More
Galactose mutarotase catalyzes the first step in normal galactose metabolism by catalyzing the conversion of beta-D-galactose to alpha-D-galactose. The structure of the enzyme from Lactococcus lactis was recently solved in this laboratory and shown to be topologically similar to domain 5 of beta-galactosidase. From this initial X-ray analysis, four amino acid residues were demonstrated to be intimately involved in sugar binding to the protein: His 96, His 170, Asp 243, and Glu 304. Here we present a combined X-ray crystallographic and kinetic analysis designed to examine the role of these residues in the reaction mechanism of the enzyme. For this investigation, the following site-directed mutant proteins were prepared: H96N, H170N, D243N, D243A, E304Q, and E304A. All of the structures of these proteins, complexed with either glucose or galactose, were solved to a nominal resolution of 1.95 A or better, and their kinetic parameters were measured against D-galactose, D-glucose, L-arabinose, or D-xylose. From these studies, it can be concluded that Glu 304 and His 170 are critical for catalysis and that His 96 and Asp 243 are important for proper substrate positioning within the active site. Specifically, Glu 304 serves as the active site base to initiate the reaction by removing the proton from the C-1 hydroxyl group of the sugar substrate and His 170 functions as the active site acid to protonate the C-5 ring oxygen. << Less
Protein Sci 12:1051-1059(2003) [PubMed] [EuropePMC]
This publication is cited by 3 other entries.
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Mutarotase from Penicillium notatum. II. The mechanism of the mutarotation reaction.
BENTLEY R., BHATE D.S.
J Biol Chem 235:1225-1233(1960) [PubMed] [EuropePMC]
This publication is cited by 1 other entry.