Linked Life Data

14690376

Source:http://linkedlifedata.com/resource/pubmed/id/14690376

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
27
pubmed:dateCreated
2003-12-23
pubmed:abstractText
The xylose-fermenting yeast Candida intermedia produces two isoforms of xylose reductase: one is NADPH-dependent (monospecific xylose reductase; msXR), and another is shown here to prefer NADH approximately 4-fold over NADPH (dual specific xylose reductase; dsXR). To compare the functional properties of the isozymes, a steady-state kinetic analysis for the reaction d-xylose + NAD(P)H + H(+) <--> xylitol + NAD(P)(+) was carried out and specificity constants (k(cat)/K(aldehyde)) were measured for the reduction of a series of aldehydes differing in side-chain size as well as hydrogen-bonding capabilities with the substrate binding pocket of the enzyme. dsXR binds NAD(P)(+) (K(iNAD+) = 70 microM; K(iNADP+) = 55 microM) weakly and NADH (K(i) = 8 microM) about as tightly as NADPH (K(i) = 14 microM). msXR shows uniform binding of NADPH and NADP(+) (K(iNADP+) approximately K(iNADPH) = 20 microM). A quantitative structure-activity relationship analysis was carried out by correlating logarithmic k(cat)/K(aldehyde) values for dsXR with corresponding logarithmic k(cat)/K(aldehyde) values for msXR. This correlation is linear with a slope of approximately 1 (r (2) = 0.912), indicating that no isozyme-related pattern of substrate specificity prevails and aldehyde-binding modes are identical in both XR forms. Binary complexes of dsXR-NADH and msXR-NADPH show the same macroscopic pK of approximately 9.0-9.5, above which the activity is lost in both enzymes. A lower pK of 7.4 is seen for dsXR-NADPH. Specificity for NADH and greater binding affinity for NAD(P)H than NAD(P)(+) are thus the main features of enzymic function that distinguish dsXR from msXR.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0021-8561
pubmed:author
pubmed:issnType
Print
pubmed:day
31
pubmed:volume
51
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
7930-5
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2003
pubmed:articleTitle
Multiple forms of xylose reductase in Candida intermedia: comparison of their functional properties using quantitative structure-activity relationships, steady-state kinetic analysis, and pH studies.
pubmed:affiliation
Institute of Biotechnology, Graz University of Technology, Petersgasse 12/I, A-8010 Graz, Austria. bernd.nidetzky@tugraz.at
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't