Enzymes of pentose biosynthesis. The quaternary structure and reacting form of transketolase from baker's yeast

Cavalieri, Susan W.; Neet, Kenneth E.; Sable, Henry Z.

doi:10.1016/0003-9861(75)90062-4

Cited by 43 publications

(23 citation statements)

References 14 publications

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“…After complete resolution the addition of ThDP and a divalent cation are absolutely necessary to restore catalytic activity [57]. It has also been shown that a loss of activity can be prevented by the addition of cofactors during the puri®cation of TKs from yeasts [20,24,57,74,124,156], consistent with the pH conditions of resolution procedures being similar to the pH conditions of optimised puri®cation protocols. In contrast, partially puri®ed mammalian TKs do not require the addition of cofactors to maintain activity.…”

Section: Cofactor Requirementsmentioning

confidence: 53%

“…Consistently, puri®ed baker's yeast TK stored under alkaline conditions appears to be less stable than the mammalian ones. A loss of more than 30% of the activity after two weeks was reported when the enzyme was stored at À208C in the presence of glycerol and dithiothreitol (DTT) at pH 7.9 [20]. However, when stored at À208C as a crystalline suspension in saturated ammonium sulphate the enzyme remained stable for months [82].…”

Section: Stability and Optimum Ph For Activitymentioning

confidence: 99%

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Properties and functions of the thiamin diphosphate dependent enzyme transketolase

Schenk

Duggleby

Nixon

1998

The International Journal of Biochemistry & Cell Biology

223

164

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This review highlights recent research on the properties and functions of the enzyme transketolase, which requires thiamin diphosphate and a divalent metal ion for its activity. The transketolase-catalysed reaction is part of the pentose phosphate pathway, where transketolase appears to control the non-oxidative branch of this pathway, although the overall¯ux of labelled substrates remains controversial. Yeast transketolase is one of several thiamin diphosphate dependent enzymes whose three-dimensional structures have been determined. Together with mutational analysis these structural data have led to detailed understanding of thiamin diphosphate catalysed reactions. In the homodimer transketolase the two catalytic sites, where dihydroxyethyl groups are transferred from ketose donors to aldose acceptors, are formed at the interface between the two subunits, where the thiazole and pyrimidine rings of thiamin diphosphate are bound. Transketolase is ubiquitous and more than 30 full-length sequences are known. The encoded protein sequences contain two motifs of high homology; one common to all thiamin diphosphate-dependent enzymes and the other a unique transketolase motif. All characterised transketolases have similar kinetic and physical properties, but the mammalian enzymes are more selective in substrate utilisation than the nonmammalian representatives. Since products of the transketolase-catalysed reaction serve as precursors for a number of synthetic compounds this enzyme has been exploited for industrial applications. Putative mutant forms of transketolase, once believed to predispose to disease, have not stood up to scrutiny. However, a modi®cation of transketolase is a marker for Alzheimer's disease, and transketolase activity in erythrocytes is a measure of thiamin nutrition. The cornea contains a particularly high transketolase concentration, consistent with the proposal that pentose phosphate pathway activity has a role in the removal of light-generated radicals. #

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Section: Cofactor Requirementsmentioning

confidence: 53%

Section: Stability and Optimum Ph For Activitymentioning

confidence: 99%

Properties and functions of the thiamin diphosphate dependent enzyme transketolase

Schenk

Duggleby

Nixon

1998

The International Journal of Biochemistry & Cell Biology

223

164

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“…The catalytic activity of transketolase is dependent on thiamine diphosphate (ThDP) and divalent cations such as Mg 2+ or Ca ~-+. The enzyme from baker's yeast, Saccharomyees cerevisiae is composed of two identical subunits with a molecular weight of 74.2 kDa per monomer [1], Sundstr6m et al, unpublished results).…”

Section: Introductionmentioning

confidence: 99%

Three‐dimensional structure of apotransketolase flexible loops at the active site enable cofactor binding

1992

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The structure determination of apotransketolase and the comparison of its three-dimensional structure with that of the holoenzyme has r,.~cealed that no large conformational changes are associated with col'actor binding. Two loops at the active site are flexible in the apoe~yme which enables ThDP to reach its binding site. Binding of the eofactor induces defined conformations for these two loops at the active site. One of these loops is directly involving in binding of the cofactors, Ca '~ and ThDP. This loop acts like a flap which closes off the diphosphate binding site. After binding of the cofactor, residues of this loop form interactions to residues or loop 383-398 from the second sabanit. These interactions stabilize the conformation of the Lwo loops from a flexible to a "closed' conformation.

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“…TK is a homodimer with a molecular mass of 74.2 kDa per monomer (1,3,4) and it has two active sites of equal catalytic activity (4,5). ThDP ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Binding of the Coenzyme and Formation of the Transketolase Active Center

Kochetov¹,

Sevostyanova²

2005

IUBMB Life (International Union of Biochemistry and Molecular B

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SummaryTransketolase (TK) is a homodimer, the simplest representative of thiamine diphosphate (ThDP)-dependent enzymes. It was first ThDP-dependent enzymes the crystal structure of which has been solved and revealed the general fold for this class of enzymes and the interactions of the non-covalently bound coenzyme ThDP with the protein component. Transketolase is a convenient model to study the structure(s) of the active center and the mechanism of action of ThDP-dependent enzymes. This review summarizes the results of studies on the kinetics of the interaction of ThDP with TK from Saccharomyces cerevisae as well as the generation of the catalytically active form of the coenzyme within the holoenzyme and formation of the enzyme's active center. IUBMB Life, 57: 491 -497, 2005 Keywords Transketolase; thiamine diphosphate; functional flexibility of enzyme; nonequivalence of active centers; iminotautomeric form of thiamine diphosphate.

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Enzymes of pentose biosynthesis. The quaternary structure and reacting form of transketolase from baker's yeast

Cited by 43 publications

References 14 publications

Properties and functions of the thiamin diphosphate dependent enzyme transketolase

Properties and functions of the thiamin diphosphate dependent enzyme transketolase

Three‐dimensional structure of apotransketolase flexible loops at the active site enable cofactor binding

Binding of the Coenzyme and Formation of the Transketolase Active Center

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