Linked Life Data

2207084

Source:http://linkedlifedata.com/resource/pubmed/id/2207084

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
27
pubmed:dateCreated
1990-11-16
pubmed:abstractText
The role of the active site residue phenylalanine-31 (Phe31) for recombinant human dihydrofolate reductase (rHDHFR) has been probed by comparing the kinetic behavior of wild-type enzyme (wt) with mutant in which Phe31 is replaced by leucine (F31L rHDHFR). At pH 7.65 the steady-state kcat is almost doubled, but the rate constant for hydride transfer is decreased to less than half that for wt enzyme, as is the rate of the obligatory isomerization of the substrate complex that precedes hydride transfer. Although steady-state measurements indicated that the mutation causes large increases in Km for both substrates, dissociation constants for many complexes are decreased. These apparent paradoxes are due to major mutation-induced decreases in rate constants (koff) for dissociation of folate, dihydrofolate, and tetrahydrofolate from all of their complexes. This results in a mechanism proceeding almost entirely by only one of the two pathways used by wt enzyme. Other consequences of these changes are a much altered dependence of steady-state kcat on pH, inhibition rather than activation by tetrahydrofolate, absence of hysteresis in transient-state kinetics, and a decrease in enzyme efficiency under physiological conditions. The results indicate that there is no quantitative correlation between dihydrofolate binding and the rate of hydride transfer for this enzyme.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
10
pubmed:volume
29
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
6428-36
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1990
pubmed:articleTitle
Kinetic investigation of the functional role of phenylalanine-31 of recombinant human dihydrofolate reductase.
pubmed:affiliation
Department of Biochemical and Clinical Pharmacology, St. Jude Children's Research Hospital, Memphis, Tennessee 38101.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't