7WRR

X-ray structure of Thermus thermophilus HB8 transketorase in complex with TPP and MES

Summary for 7WRR

• Entry DOI: 10.2210/pdb7wrr/pdb
• Descriptor: Transketolase, THIAMINE DIPHOSPHATE, CALCIUM ION, ... (5 entities in total)
• Functional Keywords: transketolase, complex, tpp, transferase
• Biological source: Thermus thermophilus HB8
• Total number of polymer chains: 4
• Total formula weight: 299565.42

Authors

Kamitori, S.,Yoshihara, A. (deposition date: 2022-01-27, release date: 2022-12-07, Last modification date: 2023-11-29)

Primary citation

Yoshihara, A.,Takamatsu, Y.,Mochizuki, S.,Yoshida, H.,Masui, R.,Izumori, K.,Kamitori, S.
Structural and biochemical characterizations of Thermus thermophilus HB8 transketolase producing a heptulose.
Appl.Microbiol.Biotechnol., 107:233-245, 2023

PubMed Abstract: Transketolase is a key enzyme in the pentose phosphate pathway in all organisms, recognizing sugar phosphates as substrates. Transketolase with a cofactor of thiamine pyrophosphate catalyzes the transfer of a 2-carbon unit from D-xylulose-5-phosphate to D-ribose-5-phosphate (5-carbon aldose), giving D-sedoheptulose-7-phosphate (7-carbon ketose). Transketolases can also recognize non-phosphorylated monosaccharides as substrates, and catalyze the formation of non-phosphorylated 7-carbon ketose (heptulose), which has attracted pharmaceutical attention as an inhibitor of sugar metabolism. Here, we report the structural and biochemical characterizations of transketolase from Thermus thermophilus HB8 (TtTK), a well-characterized thermophilic Gram-negative bacterium. TtTK showed marked thermostability with maximum enzyme activity at 85 °C, and efficiently catalyzed the formation of heptuloses from lithium hydroxypyruvate and four aldopentoses: D-ribose, L-lyxose, L-arabinose, and D-xylose. The X-ray structure showed that TtTK tightly forms a homodimer with more interactions between subunits compared with transketolase from other organisms, contributing to its thermal stability. A modeling study based on X-ray structures suggested that D-ribose and L-lyxose could bind to the catalytic site of TtTK to form favorable hydrogen bonds with the enzyme, explaining the high conversion rates of 41% (D-ribose) and 43% (L-lyxose) to heptulose. These results demonstrate the potential of TtTK as an enzyme producing a rare sugar of heptulose. KEY POINTS: • Transketolase catalyzes the formation of a 7-carbon sugar phosphate • Structural and biochemical characterizations of thermophilic transketolase were done • The enzyme could produce non-phosphorylated 7-carbon ketoses from sugars.

PubMed: 36441206
DOI: 10.1007/s00253-022-12297-z

Experimental method

X-RAY DIFFRACTION (2.01 Å)