Linked Life Data

6546755

Source:http://linkedlifedata.com/resource/pubmed/id/6546755

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
6
pubmed:dateCreated
1984-5-4
pubmed:abstractText
The optical and fluorescence characteristics of lumazine (2, 4-dihydroxypteridine) and violapterin (2,4,6-trihydroxypteridine) are described. The reduction of xanthine oxidase by excess lumazine is markedly biphasic. The initial rapid phase is about 100-fold more rapid than Vmax and reflects the reaction of the enzyme with the first equivalent of lumazine; it is accompanied by the appearance of long wavelength absorbance of the Mo(IV) violapterin charge transfer species together with partial reduction in absorbance at 450 nm, reflecting a partial transfer of electrons from the Mo to the flavin and iron-sulfur center. A loss of substrate fluorescence and a burst of fluorescence due to enzyme bound product also occur during this phase. The second phase is rate-controlled by the dissociation of violapterin from the reduced enzyme. It is accompanied by a variable loss of the charge-transfer band, further reduction of the flavin and iron-sulfur chromophores and of substrate fluorescence, and the appearance of fluorescence of unbound product. This phase correlates well with the steady state parameters. The variation in kinetic behavior with pH is qualitatively explained by a marked decrease in the affinity of the enzyme as the pH is raised; Vmax is almost unaffected by pH. The temporal sequence of kinetic events reveals at least three steps in the reaction of xanthine oxidase with the first equivalent of lumazine.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
25
pubmed:volume
259
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
3526-33
pubmed:dateRevised
2007-11-15
pubmed:meshHeading
pubmed:year
1984
pubmed:articleTitle
The reaction of xanthine oxidase with lumazine. Characterization of the reductive half-reaction.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't