Transketolase

Definition

Transketolase is an important enzyme that plays a crucial role in the pentose phosphate pathway, facilitating the transfer of two-carbon units between sugar molecules. This enzyme catalyzes the reversible reaction that converts a ketose and an aldose into different sugar phosphates, contributing to the cellular processes of nucleotide and amino acid synthesis while also helping in maintaining cellular redox balance.

5 Must Know Facts For Your Next Test

1. Transketolase requires thiamine pyrophosphate (TPP) as a cofactor for its enzymatic activity, making it dependent on vitamin B1.
2. This enzyme operates in both the oxidative and non-oxidative phases of the pentose phosphate pathway, thus linking carbohydrate metabolism with cellular energy production.
3. Deficiency of transketolase can lead to impaired nucleotide synthesis, affecting rapidly dividing cells such as those in bone marrow or tumors.
4. Transketolase activity can be influenced by the availability of substrates and cofactors, indicating its role in metabolic flexibility.
5. Measuring transketolase activity can serve as a biomarker for certain diseases, including Wernicke-Korsakoff syndrome, which is associated with thiamine deficiency.

Review Questions

• How does transketolase contribute to the pentose phosphate pathway and what are its implications for cellular metabolism?
  • Transketolase contributes to the pentose phosphate pathway by catalyzing the transfer of two-carbon units between sugars. This function allows for the conversion of different sugar phosphates which is essential for producing ribose 5-phosphate for nucleotide synthesis. This enzymatic reaction also plays a vital role in maintaining cellular redox balance by generating NADPH, which is necessary for various biosynthetic reactions and protection against oxidative stress.
• Discuss the significance of thiamine pyrophosphate as a cofactor for transketolase and its impact on human health.
  • Thiamine pyrophosphate (TPP) is crucial for the proper functioning of transketolase because it acts as a cofactor that facilitates the enzyme's catalytic activity. Without sufficient TPP, transketolase cannot effectively perform its role in the pentose phosphate pathway. This dependency on vitamin B1 underscores the importance of adequate nutrition; a deficiency can lead to metabolic disorders, such as Wernicke-Korsakoff syndrome, highlighting how enzyme deficiencies can impact overall health and function.
• Evaluate the potential clinical applications of measuring transketolase activity in diagnosing metabolic disorders.
  • Measuring transketolase activity has potential clinical applications as it can serve as a biomarker for certain metabolic disorders, especially those related to thiamine deficiency. In conditions like Wernicke-Korsakoff syndrome, low levels of transketolase activity may indicate impaired carbohydrate metabolism and associated neurological issues. By assessing enzyme activity levels, healthcare providers can diagnose metabolic imbalances early on, allowing for timely intervention and management strategies to improve patient outcomes.

Related terms

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

Aldose: A type of sugar that contains an aldehyde group, often used as a substrate in reactions involving transketolase.

NADPH: Nicotinamide adenine dinucleotide phosphate, a cofactor used in anabolic reactions, essential for biosynthetic pathways.