TKL2/YBR117C Summary Help

Standard Name TKL2
Systematic Name YBR117C
Feature Type ORF, Verified
Description Transketolase; catalyzes conversion of xylulose-5-phosphate and ribose-5-phosphate to sedoheptulose-7-phosphate and glyceraldehyde-3-phosphate in the pentose phosphate pathway; needed for synthesis of aromatic amino acids; TKL2 has a paralog, TKL1, that arose from the whole genome duplication (1, 2 and see Summary Paragraph)
Name Description TransKetoLase
Chromosomal Location
ChrII:476437 to 474392 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Gene Ontology Annotations All TKL2 GO evidence and references
  View Computational GO annotations for TKL2
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Regulators 97 genes
Classical genetics
Large-scale survey
23 total interaction(s) for 17 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 3
  • Affinity Capture-RNA: 1
  • Two-hybrid: 1

Genetic Interactions
  • Negative Genetic: 8
  • Positive Genetic: 3
  • Synthetic Growth Defect: 1
  • Synthetic Lethality: 6

Expression Summary
Length (a.a.) 681
Molecular Weight (Da) 75,029
Isoelectric Point (pI) 6.07
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrII:476437 to 474392 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Last Update Coordinates: 2011-02-03 | Sequence: 1997-01-28
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..2046 476437..474392 2011-02-03 1997-01-28
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | E.C. | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000000321

Transketolase catalyzes the transfer of a ketol from a ketose (xylulose 5-phosphate, fructose 6-phosphate or sedoheptulose 7-phosphate) to an aldose (ribose 5-phosphate, erythrose 4-phosphate or glyceraldehyde 3-phosphate) and is a key enzyme in the pentose phosphate shunt (3, 4). Transketolase, together with transaldolase, creates a reversible link between two main metabolic pathways, the pentose phosphate pathway and glycolysis, which allows the cell to adapt its NADPH production, and ribose-5-phosphate production to meet its immediate needs (3). In Saccharomyces cerevisiae, TKL1 encodes the major isoform and TKL2 encodes a minor isoform (1). Double null mutants for tkl1 and tkl2 are viable, but auxotrophic for aromatic amino acids (1).

Transketolase from S. cerevisiae, is a homodimer, and is dependent on thiamine diphosphate as a cofactor and on divalent cations for activity (5, 3, 6, 7, 8, 9). Each subunit is folded into three consecutive alpha/beta-domains (3). The coenzyme-binding site is located in a deep cleft at the interface between the subunits, and residues of both subunits interact with the thiamine diphosphate cofactor (3, 10, 11, 12) to stabilize the holoenyme. Binding of Ca2+, or to a lesser extent of Mg2+, also stabilize the holoenzyme (12). In vivo, transketolase activity may be negatively regulated by RNA (13). Each is also capable of nonspecifically catalyzing the reactions in the non-oxidative branch of the pentose phosphate pathway (4).

Although transketolase activity is not detectable in tkl1 null mutants, Tkl2p is expressed and does play a physiological role (1). Expression of TKL2 is induced in carbon-limited (low glucose) cultures, in response to lithium chloride or dimethyl sulfoxide (DMSO), and at the diauxic transition in a Msn2/4p-dependent manner, and TKL2 expression is repressed in response to cAMP (14, 15, 16, 17). Tkl2p localizes to the nucleus and cytoplasm (18).

Tkl2p has similarity to S. cerevisiae Tkl1p, Escherichia coli transketolase, Rhodobacter sphaeroides transketolase, Streptococcus pneumoniae recP, Hansenula polymorpha dihydroxyacetone synthase, Kluyveromyces lactis TKL1 (which complements the phenotype of the tkl1 tkl2 double null mutant (19)), Pichia stipitis TKT, rabbit liver transketolase, rat TKT, mouse TKT, and human TKT (1, 5, 8, 19). Tkl2p is also related to E. coli pyruvate dehydrogenase E1 subunit, which is another vitamin B1-dependent enzyme (5).

Last updated: 2005-12-19 Contact SGD

References cited on this page View Complete Literature Guide for TKL2
1) Schaaff-Gerstenschlager I, et al.  (1993) TKL2, a second transketolase gene of Saccharomyces cerevisiae. Cloning, sequence and deletion analysis of the gene. Eur J Biochem 217(1):487-92
2) Byrne KP and Wolfe KH  (2005) The Yeast Gene Order Browser: combining curated homology and syntenic context reveals gene fate in polyploid species. Genome Res 15(10):1456-61
3) Lindqvist Y, et al.  (1992) Three-dimensional structure of transketolase, a thiamine diphosphate dependent enzyme, at 2.5 A resolution. EMBO J 11(7):2373-9
4) Kleijn RJ, et al.  (2005) Revisiting the 13C-label distribution of the non-oxidative branch of the pentose phosphate pathway based upon kinetic and genetic evidence. FEBS J 272(19):4970-82
5) Sundstrom M, et al.  (1993) Yeast TKL1 gene encodes a transketolase that is required for efficient glycolysis and biosynthesis of aromatic amino acids. J Biol Chem 268(32):24346-52
6) Nikkola M, et al.  (1994) Refined structure of transketolase from Saccharomyces cerevisiae at 2.0 A resolution. J Mol Biol 238(3):387-404
7) Schneider G, et al.  (1989) Preliminary crystallographic data for transketolase from yeast. J Biol Chem 264(36):21619-20
8) Fletcher TS, et al.  (1992) DNA sequence of the yeast transketolase gene. Biochemistry 31(6):1892-6
9) Nilsson U, et al.  (1997) Examination of substrate binding in thiamin diphosphate-dependent transketolase by protein crystallography and site-directed mutagenesis. J Biol Chem 272(3):1864-9
10) Golbik R, et al.  (2005) Effect of coenzyme modification on the structural and catalytic properties of wild-type transketolase and of the variant E418A from Saccharomyces cerevisiae. FEBS J 272(6):1326-42
11) Muller YA, et al.  (1993) A thiamin diphosphate binding fold revealed by comparison of the crystal structures of transketolase, pyruvate oxidase and pyruvate decarboxylase. Structure 1(2):95-103
12) Esakova OA, et al.  (2005) Effects of transketolase cofactors on its conformation and stability. Life Sci 78(1):8-13
13) Tikhomirova NK, et al.  (1990) A new form of baker's yeast transketolase. An enzyme-RNA complex. FEBS Lett 274(1-2):27-9
14) Boer VM, et al.  (2003) The genome-wide transcriptional responses of Saccharomyces cerevisiae grown on glucose in aerobic chemostat cultures limited for carbon, nitrogen, phosphorus, or sulfur. J Biol Chem 278(5):3265-74
15) Bro C, et al.  (2003) Transcriptional, proteomic, and metabolic responses to lithium in galactose-grown yeast cells. J Biol Chem 278(34):32141-9
16) Zhang W, et al.  (2003) Microarray analyses of the metabolic responses of Saccharomyces cerevisiae to organic solvent dimethyl sulfoxide. J Ind Microbiol Biotechnol 30(1):57-69
17) Boy-Marcotte E, et al.  (1998) Msn2p and Msn4p control a large number of genes induced at the diauxic transition which are repressed by cyclic AMP in Saccharomyces cerevisiae. J Bacteriol 180(5):1044-52
18) Huh WK, et al.  (2003) Global analysis of protein localization in budding yeast. Nature 425(6959):686-91
19) Jacoby JJ and Heinisch JJ  (1997) Analysis of a transketolase gene from Kluyveromyces lactis reveals that the yeast enzymes are more related to transketolases of prokaryotic origins than to those of higher eukaryotes. Curr Genet 31(1):15-21