Linked Life Data

15786714

Source:http://linkedlifedata.com/resource/pubmed/id/15786714

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1-2
pubmed:dateCreated
2005-3-24
pubmed:abstractText
Polyhydroxyalkanoates (PHAs) are polyesters of hydroxyalkanoates (HAs) synthesised by numerous bacteria as intracellular carbon and energy storage compounds which accumulate as granules in the cytoplasm of the cells. The biosynthesis of PHAs, in the thermophilic bacterium T. thermophilus grown in a mineral medium supplemented with sodium gluconate as sole carbon source has been recently reported. Here, we report the purification at apparent homogeneity of a beta-ketoacyl-CoA thiolase from T. thermophilus, the first enzyme of the most common biosynthetic pathway for PHAs. B-Ketoacyl-CoA thiolase appeared as a single band of 45.5-kDa molecular mass on SDS/PAGE. The enzyme was purified 390-fold with 7% recovery. The native enzyme is a multimeric protein of a molecular mass of approximately of 182 kDa consisting of four identical subunits of 45.5 kDa, as identified by an in situ renaturation experiment on SDS-PAGE. The enzyme exhibited an optimal pH of approximately 8.0 and highest activity at 65 degrees C for both direction of the reaction. The thiolysis reaction showed a substrate inhibition at high concentrations; when one of the substrates (acetoacetyl CoA or CoA) is varied, while the concentrations of the second substrates (CoA or acetoacetyl CoA respectively) remain constant. The initial velocity kinetics showed a pattern of a family of parallel lines, which is in accordance with a ping-pong mechanism. beta-Ketothiolase had a relative low Km of 0.25 mM for acetyl-CoA and 11 microM and 25 microM for CoA and acetoacetyl-CoA, respectively. The enzyme was inhibited by treatment with 1 mM N-ethylmaleimide either in the presence or in the absence of 0.5 mM of acetyl-CoA suggesting that possibly a cysteine is located at/or near the active site of beta-ketothiolase.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0300-8177
pubmed:author
pubmed:issnType
Print
pubmed:volume
269
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
27-36
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed:year
2005
pubmed:articleTitle
A thermostable beta-ketothiolase of polyhydroxyalkanoates (PHAs) in Thermus thermophilus: purification and biochemical properties.
pubmed:affiliation
Laboratory of Biochemistry, Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
pubmed:publicationType
Journal Article