Linked Life Data

6428467

Source:http://linkedlifedata.com/resource/pubmed/id/6428467

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
1984-8-22
pubmed:abstractText
Kinetic and allosteric propeties of highly purified "biosynthetic" L-threonine dehydratase from brewer's yeast S. carlbergensis were studied at three pH values, using L-threonine and L-serine as substrates. It was shown that the plot of the initial reaction rate (v) versus initial substrate concentrations ([S]0 pH 6.5 is hyperbolic (Km=5.0.10-2M), while these at pH 7.8 and 9.5 have a faintly pronounced sigmoidal shape with fast occurring saturation plateaus ([S]0.5= 1.0.10-2 and 0.9.10-2M, respectively). the ratios between L-threonine and L-serine dehydratation rates depend on pH. The kinetic properties and the dependence of substrate specificity on pH suggest that the enzyme molecule undergoes pH-induced (at pH 7.0) conformational changes. The determination of pK values of the enzyme functional groups involved in L-threonine binding demonstrated that these groups have pK is approximately equal to 7.5 and 9.5. The latter group was hypothetically identified as a epsilon-NH2-group of the lysine residue. High concentrations of the allosteric inhibitor (L-isoleucine) decrease the rates of L-threonine and L-serine dehydratation and induce the appearance (at pH 6.5) or increase (at pH 7.9 and 9.5) of homotropic cooperative interactions between the active sites in the course of L-threonine dehydratation. The enzyme inhibition by L-isoleucine increases with a decrease of L-threonine concentrations. Low L-isoleucine concentrations, as well as the enzyme activator (L-valine) stimulate the enzyme at non-saturating substrate concentrations (when L-threonine or L-serine are used as substrates) without normalization of (v) versus [S]0 plots. The maximal activation of the enzyme is observed at pHG 8.5--9.0. It is assumed that the molecule of "biosynthetic" L-threonine dehydratase from brewer's yeast contains two types of sites responsible for the effector binding, i.e., "activatory" and "inhibitory" ones.
pubmed:language
rus
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0320-9725
pubmed:author
pubmed:issnType
Print
pubmed:volume
49
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
540-6
pubmed:dateRevised
2007-7-23
pubmed:meshHeading
pubmed:year
1984
pubmed:articleTitle
[Kinetic and allosteric properties of highly-purified, biosynthetic L-threonine dehydrogenase from brewer's yeast Saccharomyces carlsbergensis].
pubmed:publicationType
Journal Article, English Abstract