3KHU

Crystal structure of human UDP-glucose dehydrogenase Glu161Gln, in complex with thiohemiacetal intermediate


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.3 Å
  • R-Value Free: 0.225 
  • R-Value Work: 0.195 

wwPDB Validation 3D Report Full Report


This is version 1.4 of the entry. See complete history

Literature

Structural and Kinetic Evidence That Catalytic Reaction of Human UDP-glucose 6-Dehydrogenase Involves Covalent Thiohemiacetal and Thioester Enzyme Intermediates.

Egger, S.Chaikuad, A.Klimacek, M.Kavanagh, K.L.Oppermann, U.Nidetzky, B.

(2012) J.Biol.Chem. 287: 2119-2129

  • DOI: 10.1074/jbc.M111.313015

  • PubMed Abstract: 
  • Biosynthesis of UDP-glucuronic acid by UDP-glucose 6-dehydrogenase (UGDH) occurs through the four-electron oxidation of the UDP-glucose C6 primary alcohol in two NAD(+)-dependent steps. The catalytic reaction of UGDH is thought to involve a Cys nucle ...

    Biosynthesis of UDP-glucuronic acid by UDP-glucose 6-dehydrogenase (UGDH) occurs through the four-electron oxidation of the UDP-glucose C6 primary alcohol in two NAD(+)-dependent steps. The catalytic reaction of UGDH is thought to involve a Cys nucleophile that promotes formation of a thiohemiacetal enzyme intermediate in the course of the first oxidation step. The thiohemiacetal undergoes further oxidation into a thioester, and hydrolysis of the thioester completes the catalytic cycle. Herein we present crystallographic and kinetic evidence for the human form of UGDH that clarifies participation of covalent catalysis in the enzymatic mechanism. Substitution of the putative catalytic base for water attack on the thioester (Glu(161)) by an incompetent analog (Gln(161)) gave a UGDH variant (E161Q) in which the hydrolysis step had become completely rate-limiting so that a thioester enzyme intermediate accumulated at steady state. By crystallizing E161Q in the presence of 5 mm UDP-glucose and 2 mm NAD(+), we succeeded in trapping a thiohemiacetal enzyme intermediate and determined its structure at 2.3 Å resolution. Cys(276) was covalently modified in the structure, establishing its role as catalytic nucleophile of the reaction. The thiohemiacetal reactive C6 was in a position suitable to become further oxidized by hydride transfer to NAD(+). The proposed catalytic mechanism of human UGDH involves Lys(220) as general base for UDP-glucose alcohol oxidation and for oxyanion stabilization during formation and breakdown of the thiohemiacetal and thioester enzyme intermediates. Water coordinated to Asp(280) deprotonates Cys(276) to function as an aldehyde trap and also provides oxyanion stabilization. Glu(161) is the Brønsted base catalytically promoting the thioester hydrolysis.


    Organizational Affiliation

    Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, A-8010 Graz, Austria.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
UDP-glucose 6-dehydrogenase
A, B, C, D, E, F
467Homo sapiensMutation(s): 1 
Gene Names: UGDH
EC: 1.1.1.22
Find proteins for O60701 (Homo sapiens)
Go to Gene View: UGDH
Go to UniProtKB:  O60701
Small Molecules
Ligands 3 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
EPE
Query on EPE

Download SDF File 
Download CCD File 
D
4-(2-HYDROXYETHYL)-1-PIPERAZINE ETHANESULFONIC ACID
HEPES
C8 H18 N2 O4 S
JKMHFZQWWAIEOD-UHFFFAOYSA-N
 Ligand Interaction
UPG
Query on UPG

Download SDF File 
Download CCD File 
A, B, C, D, E, F
URIDINE-5'-DIPHOSPHATE-GLUCOSE
URIDINE-5'-MONOPHOSPHATE GLUCOPYRANOSYL-MONOPHOSPHATE ESTER
C15 H24 N2 O17 P2
HSCJRCZFDFQWRP-JZMIEXBBSA-N
 Ligand Interaction
EDO
Query on EDO

Download SDF File 
Download CCD File 
A, B, C, E
1,2-ETHANEDIOL
ETHYLENE GLYCOL
C2 H6 O2
LYCAIKOWRPUZTN-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.3 Å
  • R-Value Free: 0.225 
  • R-Value Work: 0.195 
  • Space Group: P 21 21 2
Unit Cell:
Length (Å)Angle (°)
a = 203.540α = 90.00
b = 207.340β = 90.00
c = 93.400γ = 90.00
Software Package:
Software NamePurpose
ADSCdata collection
MOSFLMdata reduction
SCALAdata scaling
REFMACrefinement
PHASERphasing

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Revision History 

  • Version 1.0: 2009-11-17
    Type: Initial release
  • Version 1.1: 2011-07-13
    Type: Advisory, Version format compliance
  • Version 1.2: 2011-12-07
    Type: Database references
  • Version 1.3: 2012-01-11
    Type: Database references
  • Version 1.4: 2012-02-01
    Type: Database references