Transketolase

Definition

Transketolase is an essential enzyme that facilitates the transfer of two-carbon units in the pentose phosphate pathway, specifically converting xylulose-5-phosphate and ribose-5-phosphate into sedoheptulose-7-phosphate and glyceraldehyde-3-phosphate. This enzyme plays a crucial role in linking carbohydrate metabolism with nucleotide synthesis, thus contributing to cellular metabolism and energy production.

5 Must Know Facts For Your Next Test

1. Transketolase requires thiamine pyrophosphate (TPP) as a cofactor to function, which is vital for its enzymatic activity.
2. This enzyme operates in the non-oxidative phase of the pentose phosphate pathway, which is crucial for generating sugars necessary for nucleotide synthesis.
3. Deficiency in transketolase can lead to impaired cellular metabolism, particularly affecting rapidly dividing cells like those in the immune system and bone marrow.
4. Transketolase activity is often measured as an indicator of cellular health and metabolic status, especially in conditions related to thiamine deficiency.
5. It helps regulate the flow of carbon skeletons between the pentose phosphate pathway and glycolysis, illustrating its role in coordinating energy and metabolic needs.

Review Questions

• How does transketolase function within the pentose phosphate pathway and what are its primary substrates?
  • Transketolase functions by transferring two-carbon units from xylulose-5-phosphate to ribose-5-phosphate, producing sedoheptulose-7-phosphate and glyceraldehyde-3-phosphate. This process is crucial as it enables the interconversion of sugars, allowing cells to balance their metabolic needs. The enzyme's activity supports nucleotide synthesis while linking carbohydrate metabolism with other essential pathways.
• Discuss the significance of thiamine pyrophosphate as a cofactor for transketolase and how this relates to metabolic health.
  • Thiamine pyrophosphate (TPP) is vital for transketolase's function as it acts as a coenzyme, facilitating the transfer of carbon units during reactions. A deficiency in thiamine can impair transketolase activity, leading to metabolic dysfunctions and conditions such as Wernicke-Korsakoff syndrome. This emphasizes the importance of adequate nutrient levels for maintaining metabolic health and proper enzymatic functions.
• Evaluate the role of transketolase in linking the pentose phosphate pathway to broader cellular metabolism, including its impact on energy production.
  • Transketolase plays a pivotal role in connecting the pentose phosphate pathway with glycolysis by converting pentose phosphates into hexose phosphates. This interconnection allows for flexibility in cellular metabolism, enabling cells to adjust their energy production based on immediate needs. By generating intermediates that feed into glycolysis, transketolase enhances overall energy yield while supporting nucleotide synthesis, highlighting its integral role in cellular function and homeostasis.

Related terms

Pentose Phosphate Pathway: A metabolic pathway that generates NADPH and ribose 5-phosphate for nucleotide synthesis while providing intermediates for glycolysis.

NADPH: A coenzyme that acts as a reducing agent in various biochemical reactions, critical for biosynthetic processes and maintaining redox balance in cells.

Ribulose-5-phosphate: A pentose sugar phosphate that is a key intermediate in the pentose phosphate pathway and can be converted into ribose-5-phosphate.