TKL1/YPR074C Summary Help

Standard Name TKL1
Systematic Name YPR074C
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; TKL1 has a paralog, TKL2, that arose from the whole genome duplication (1, 2, 3 and see Summary Paragraph)
Name Description TransKetoLase
Chromosomal Location
ChrXVI:694838 to 692796 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Gene Ontology Annotations All TKL1 GO evidence and references
  View Computational GO annotations for TKL1
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 144 genes
Classical genetics
Large-scale survey
132 total interaction(s) for 103 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 24
  • Affinity Capture-RNA: 5
  • Biochemical Activity: 1
  • PCA: 1
  • Protein-peptide: 6
  • Reconstituted Complex: 2

Genetic Interactions
  • Dosage Rescue: 3
  • Negative Genetic: 67
  • Phenotypic Suppression: 3
  • Positive Genetic: 10
  • Synthetic Growth Defect: 3
  • Synthetic Lethality: 6
  • Synthetic Rescue: 1

Expression Summary
Length (a.a.) 680
Molecular Weight (Da) 73,805
Isoelectric Point (pI) 7.01
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrXVI:694838 to 692796 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..2043 694838..692796 2011-02-03 1996-07-31
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 SGDIDS000006278

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 (4, 5). 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 (4). In Saccharomyces cerevisiae, TKL1 encodes the major isoform and TKL2 encodes a minor isoform (6). Double null mutants for tkl1 and tkl2 are viable, but auxotrophic for aromatic amino acids (6).

Transketolase from S. cerevisiae, is a homodimer, and is dependent on thiamine diphosphate as a cofactor and on divalent cations for activity (1, 4, 7, 8, 9, 10). Each subunit is folded into three consecutive alpha/beta-domains (4). 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 (4, 11, 12, 13) to stabilize the holoenyme. Binding of Ca2+, or to a lesser extent of Mg2+, also stabilize the holoenzyme (13). In vivo, transketolase activity may be negatively regulated by RNA (14). Each is also capable of nonspecifically catalyzing the reactions in the non-oxidative branch of the pentose phosphate pathway (5).

The Tkl1p enzyme is well characterized. Specific amino acids have shown to be important for specific activities, such as stability of the Tkl1p transketolase holoenzyme (15), coenzyme binding (10, 15), substrate specificity and enzymatic activity (10, 11, 16, 17, 18). In addition to catalyzing the common two-substrate transketolase reaction, Tkl1p has also specifically been shown to catalyze a one-substrate reaction utilizing only xylulose 5-phosphate to produce glyceraldehyde 3-phosphate and erythrulose (19).

Null tkl1 mutants are viable and display normal growth on rich media, but display different growth defects on minimal media depending on the strain background (1, 6, 11, 15, 16, 20). Tkl1p is required for efficient use of fermentable carbon sources and for the biosynthesis of aromatic amino acids (1). Tkl1p is also indirectly involved in the response to reactive oxygen species (ROS) through its involvement in determining intracellular NADPH levels (21). Overexpression of TKL1 reduces growth on fermentable carbon sources, such as glucose and raffinose, and on gluconeogenic carbon sources, such as pyruvate, ethanol, and glycerol. This is similar to the phenotype of strains disrupted for TKL1 and suggests that a proper balance between glycolysis and the pentose phosphate pathway is important for efficient use of fermentable carbon sources (1).

Tkl1p is of industrial interest for the fermentation of xylose to ethanol (2). Xylose is the predominant sugar found in biomass such as agricultural wastes, wood, municipal solid wastes, and wastes from pulp and paper industries, and possibly could serve as a low-cost and abundant raw material for fuel ethanol production (22). Tkl1p expression is increased in mutant strains that display increased fitness during growth on xylose relative to the parental strain, which was engineered to utilize xylose (23, 24). These and other data suggest that TKL1 may be a good target for improving xylose fermentation in S. cerevisiae (2, 22, 23, 24, 25).

Tkl1p has similarity to S. cerevisiae Tkl2p, 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, (26)), Pichia stipitis TKT, rabbit liver transketolase, rat TKT, mouse TKT, and human TKT (1, 6, 9, 26). Tkl1p is also related to E. coli pyruvate dehydrogenase E1 subunit, which is another vitamin B1-dependent enzyme (1).

Last updated: 2005-12-19 Contact SGD

References cited on this page View Complete Literature Guide for TKL1
1) 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
2) Walfridsson M, et al.  (1995) Xylose-metabolizing Saccharomyces cerevisiae strains overexpressing the TKL1 and TAL1 genes encoding the pentose phosphate pathway enzymes transketolase and transaldolase. Appl Environ Microbiol 61(12):4184-90
3) 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
4) 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
5) 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
6) 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
7) Nikkola M, et al.  (1994) Refined structure of transketolase from Saccharomyces cerevisiae at 2.0 A resolution. J Mol Biol 238(3):387-404
8) Schneider G, et al.  (1989) Preliminary crystallographic data for transketolase from yeast. J Biol Chem 264(36):21619-20
9) Fletcher TS, et al.  (1992) DNA sequence of the yeast transketolase gene. Biochemistry 31(6):1892-6
10) 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
11) 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
12) 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
13) Esakova OA, et al.  (2005) Effects of transketolase cofactors on its conformation and stability. Life Sci 78(1):8-13
14) Tikhomirova NK, et al.  (1990) A new form of baker's yeast transketolase. An enzyme-RNA complex. FEBS Lett 274(1-2):27-9
15) Meshalkina L, et al.  (1997) Examination of the thiamin diphosphate binding site in yeast transketolase by site-directed mutagenesis. Eur J Biochem 244(2):646-52
16) Wikner C, et al.  (1995) His103 in yeast transketolase is required for substrate recognition and catalysis. Eur J Biochem 233(3):750-5
17) Kovina M, et al.  (1996) Localization of reactive tyrosine residues of baker's yeast transketolase. FEBS Lett 392(3):293-4
18) Nilsson U, et al.  (1998) Asp477 is a determinant of the enantioselectivity in yeast transketolase. FEBS Lett 424(1-2):49-52
19) Bykova IA, et al.  (2001) One-substrate transketolase-catalyzed reaction. Biochem Biophys Res Commun 280(3):845-7
20) Schaaff-Gerstenschlager I and Zimmermann FK  (1993) Pentose-phosphate pathway in Saccharomyces cerevisiae: analysis of deletion mutants for transketolase, transaldolase, and glucose 6-phosphate dehydrogenase. Curr Genet 24(5):373-6
21) Carter CD, et al.  (2005) Loss of SOD1 and LYS7 sensitizes Saccharomyces cerevisiae to hydroxyurea and DNA damage agents and downregulates MEC1 pathway effectors. Mol Cell Biol 25(23):10273-85
22) Gorsich SW, et al.  (2006) Tolerance to furfural-induced stress is associated with pentose phosphate pathway genes ZWF1, GND1, RPE1, and TKL1 in Saccharomyces cerevisiae. Appl Microbiol Biotechnol 71(3):339-49
23) Wahlbom CF, et al.  (2003) Molecular analysis of a Saccharomyces cerevisiae mutant with improved ability to utilize xylose shows enhanced expression of proteins involved in transport, initial xylose metabolism, and the pentose phosphate pathway. Appl Environ Microbiol 69(2):740-6
24) Pitkanen JP, et al.  (2005) Xylose chemostat isolates of Saccharomyces cerevisiae show altered metabolite and enzyme levels compared with xylose, glucose, and ethanol metabolism of the original strain. Appl Microbiol Biotechnol 67(6):827-37
25) Toivari MH, et al.  (2004) Endogenous xylose pathway in Saccharomyces cerevisiae. Appl Environ Microbiol 70(6):3681-6
26) 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