Linked Life Data

11437361

Source:http://linkedlifedata.com/resource/pubmed/id/11437361

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
2001-7-4
pubmed:abstractText
The flavoprotein dihydroorotate dehydrogenase (DHOD) catalyzes the oxidation of dihydroorotate to orotate. Dihydrooxonate is an analogue of dihydroorotate in which the C5 carbon is substituted by a nitrogen atom. We have investigated dihydrooxonate as a substrate of three DHODs, each representing a distinct evolutionary class of the enzyme, namely the two family 1 enzymes from Lactococcus lactis, DHODA and DHODB, and the enzyme from Escherichia coli, which, like the human enzyme, belongs to family 2. Dihydrooxonate was accepted as a substrate although much less efficiently than dihydroorotate. The first half-reaction was rate limiting according to pre-steady-state and steady-state kinetics with different electron acceptors. Cysteine and serine have been implicated as active site base residues, which promote substrate oxidation in family 1 and family 2 DHODs, respectively. Mutants of DHODA (C130A) and E. coli DHOD (S175A) have extremely low activity in standard assays with dihydroorotate as substrate, but with dihydrooxonate the mutants display considerable and increasing activity above pH 8.0. Thus, the absence of the active site base residue in the enzymes seems to be compensated for by a lower pK(a) of the 5-position in the substrate. Oxonate, the oxidation product of dihydrooxonate, was a competitive inhibitor versus dihydroorotate, and DHODA was the most sensitive of the three enzymes. DHODA was reinvestigated with respect to product inhibition by orotate. The results suggest a classical one-site ping-pong mechanism with fumarate as electron acceptor, while the kinetics with ferricyanide is highly dependent on the detailed reaction conditions.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0003-9861
pubmed:author
pubmed:copyrightInfo
Copyright 2001 Academic Press.
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
391
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
286-94
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
2001
pubmed:articleTitle
Dihydrooxonate is a substrate of dihydroorotate dehydrogenase (DHOD) providing evidence for involvement of cysteine and serine residues in base catalysis.
pubmed:affiliation
Department of Biological Chemistry, University of Copenhagen, Denmark.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't