Linked Life Data

2681195

Source:http://linkedlifedata.com/resource/pubmed/id/2681195

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
31
pubmed:dateCreated
1989-11-28
pubmed:abstractText
Incubation of homogeneous preparations of L-threonine dehydrogenase from Escherichia coli with 2,3-butanedione, 2,3-pentanedione, phenylglyoxal, or 1,2-cyclohexanedione causes a time- and concentration-dependent loss of enzymatic activity; plots of log percent activity remaining versus time are linear to greater than 90% inactivation, indicative of pseudo-first order inactivation kinetics. The reaction order with respect to the concentration of modifying reagent is approximately 1.0 in each case suggesting that the loss of catalytic activity is due to one molecule of modifier reacting with each active unit of enzyme. Controls establish that this inactivation is not due to modifier-induced dissociation or photoinduced nonspecific alteration of the dehydrogenase. Essentially the same Km but decreased Vmax values are obtained when partially inactivated enzyme is compared with native. NADH (25 mM) and NAD+ (70 mM) give full protection against inactivation whereas much higher concentrations (i.e. 150 mM) of L-threonine or L-threonine amide provide a maximum of 80-85% protection. Amino acid analyses coupled with quantitative sulfhydryl group determinations show that enzyme inactivated 95% by 2,3-butanedione loses 7.5 arginine residues (out of 16 total)/enzyme subunit with no significant change in other amino acid residues. In contrast, only 2.4 arginine residues/subunit are modified in the presence of 80 mM NAD+. Analysis of the course of modification and inactivation by the statistical method of Tsou (Tsou, C.-L. (1962) Sci. Sin. 11, 1535-1558) demonstrates that inactivation of threonine dehydrogenase correlates with the loss of 1 "essential" arginine residue/subunit which quite likely is located in the NAD+/NADH binding site.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Nov
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
5
pubmed:volume
264
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
18296-301
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1989
pubmed:articleTitle
Inactivation of Escherichia coli L-threonine dehydrogenase by 2,3-butanedione. Evidence for a catalytically essential arginine residue.
pubmed:affiliation
Department of Biological Chemistry, The University of Michigan, Ann Arbor 48109-0606.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.