Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Some properties of homogeneous transketolase from pig liver were studied. It was shown that the pH optimum of the transketolase reaction lies within the range of 7.8--8.2. The isoelectric point is at pH 7.6--7.8. The molecular weight of transketolase is 138,000 +/- 3,000 as determined by the sedimentation equilibrium method and about 152,000 according to the data from gel filtration through Sephadex G-200. The enzyme molecule is a tetramer of the alpha 2 beta 2 type. The molecular weights of the alpha- and beta- subunits determined by polyacrylamide gel in the presence of sodium dodecyl sulfate are 52,000--56,000 and 27,000--29,000, respectively. Transketolase contains about two moles of TPP per mole of protein and does not require metal ions for its catalytic activity.
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PMID:[Properties of pig liver transketolase]. 46 97

Transketolase was isolated from wet tissue of rat liver and purified by ammonium sulfate and CM-cellulose fractionation and by adsorption chromatography on hydroxylapatite. The native enzyme is made up of two subunits with molecular weight of 70 000, is electrophoretically homogeneous and has a specific activity of 2.8 u. per mg of protein (30 degrees). The enzymatic and fluorimetric assays revealed the presence of two moles of thiamine diphosphate per mole of protein. The Arrhenius plots for the rate of the transketolase reaction with a pentose phosphate mixture as substrate are continuous at 10-32 degrees; the activation energy is 89.9 cJ/mole, temperature index is 3.3. The curve for the reaction rate versus substrate concentration is S-shaped; the apparent Km value for xylulose 5-phosphate is 2.2 x 10(-5) M. The ions with a tetraedric structure (arsenate, phosphate, sulfate) act as competitive inhibitors of the transketolase-catalyzed reaction.
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PMID:[Purification and properties of rat liver transketolase]. 731 24