Crystallographic evidence for Tyr 157 functioning as the active site base in human UDP-galactose 4-epimerase.

@article{Thoden2000CrystallographicEF,
  title={Crystallographic evidence for Tyr 157 functioning as the active site base in human UDP-galactose 4-epimerase.},
  author={J. Thoden and T. M. Wohlers and J. Fridovich-Keil and H. Holden},
  journal={Biochemistry},
  year={2000},
  volume={39 19},
  pages={
          5691-701
        }
}
UDP-galactose 4-epimerase catalyzes the interconversion of UDP-glucose and UDP-galactose during normal galactose metabolism. In humans, deficiencies in this enzyme lead to the complex disorder referred to as epimerase-deficiency galactosemia. Here, we describe the high-resolution X-ray crystallographic structures of human epimerase in the resting state (i.e., with bound NAD(+)) and in a ternary complex with bound NADH and UDP-glucose. Those amino acid side chains responsible for anchoring the… Expand
Human UDP-galactose 4-Epimerase
TLDR
The three-dimensional structure of human epimerase complexed with NADH and UDP-GlcNAc is described and it is shown that in the human enzyme, the structural equivalent of Tyr-299 in the E. coli protein is replaced with a cysteine residue and the active site volume is calculated to be ∼15% larger than that observed for the bacterial epimer enzyme. Expand
Determinants of Function and Substrate Specificity in Human UDP-galactose 4′-Epimerase*
TLDR
Results serve to validate the wild-type hGALE crystal structure and fully support the hypothesis that residue 307 acts as a gatekeeper mediating substrate access to the hGale active site. Expand
Structural Analysis of the Y299C Mutant of Escherichia coli UDP-galactose 4-Epimerase
TLDR
It was previously postulated that the additional activity in the human epimerase was due to replacement of the structural equivalent of Tyr-299 in the E. coli enzyme with a cysteine residue, thereby leading to a larger active site volume, and studies have revealed that this simple mutation did confer UDP-GalNAc/UDP-GlcNAc converting activity to the bacterial enzyme with minimal changes in its three-dimensional structure. Expand
The structural basis of substrate promiscuity in UDP-hexose 4-epimerase from the hyperthermophilic Eubacterium Thermotoga maritima.
TLDR
The data showed that TM0509 is a UDP-galactosugar 4-epimerase involved in d- GalE metabolism; consequently, this study provides the first detailed characterization of a hyperthermophilic GalE, and supports the notion that TMGalE might exhibit the earliest form of sugar-epimizing enzymes in the evolution of galactose metabolism. Expand
Comparison of dynamics of wildtype and V94M human UDP-galactose 4-epimerase-A computational perspective on severe epimerase-deficiency galactosemia.
TLDR
Greater active site loop mobility in human GALE compared to the equivalent loop in Escherichia coli GALE explains why the former can catalyze the interconversion of UDP-N-acetylgalactosamine and UDP- nacetylglucosamine while the bacterial enzyme cannot. Expand
Disturbed cofactor binding by a novel mutation in UDP-galactose 4′-epimerase results in a type III galactosemia phenotype at birth
UDP-galactose 4′-epimerase (GALE) is an essential enzyme in galactose metabolism and its dysfunction results in type III galactosemia. Herein we report a patient born with abnormal blood galactoseExpand
Molecular Structure of Galactokinase*
TLDR
The structure of galactokinase described here serves as a model for understanding the functional consequences of point mutations known to result in Type II galactosemia in humans. Expand
Crystal structure of UDP-galactose 4-epimerase from the hyperthermophilic archaeon Pyrobaculum calidifontis.
TLDR
Structural comparison revealed that the presence of an extensive hydrophobic interaction at the subunit interface is likely the main factor contributing to the hyperthermostability of the P. calidifontis enzyme. Expand
Structure of an antibiotic-synthesizing UDP-glucuronate 4-epimerase MoeE5 in complex with substrate.
  • H. Sun, T. Ko, +4 authors R. Guo
  • Chemistry, Medicine
  • Biochemical and biophysical research communications
  • 2019
TLDR
As the first complex structure of this protein family with a bound UDP-GlcA in the active site, MoeE5 shows an extensive hydrogen-bond network between the enzyme and the substrate, suggesting it is likely a specific epimerase for UDP- GlcA to UDP-GalA conversion, rather than a promiscuous enzyme as some other family members. Expand
Insights into role of the hydrogen bond networks in substrate recognition by UDP-GalNAc 4-epimerases.
TLDR
An analysis of the proposed model of substrate recognition using site-directed mutagenesis of WBGU and crystal structure of the His305Ala mutant reveals that the wild-type activity of WbgU is retained in most single-point mutants targeting the active site, and it is inferred that the specific and non-specific interactions throughout theactive site confer it sufficient elasticity to sustain wild- type activity for several of the single- point mutations. Expand
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