Transketolase activity is seen with which vitamin
**Core Concept**
Transketolase is an enzyme involved in the pentose phosphate pathway, which generates NADPH and pentoses from glucose-6-phosphate. This pathway is crucial for biosynthesis and antioxidant defense mechanisms in cells. The activity of transketolase is dependent on thiamine pyrophosphate (TPP), which is the active form of thiamine (vitamin B1).
**Why the Correct Answer is Right**
Thiamine pyrophosphate (TPP) is the coenzyme required for transketolase activity. TPP is formed when thiamine is converted to its active form through a reaction involving thiamine pyrophosphokinase. The pentose phosphate pathway, where transketolase plays a key role, is essential for generating NADPH, which is necessary for fatty acid synthesis and reducing glutathione. In addition, the pentose phosphate pathway produces ribose-5-phosphate, a precursor for nucleotide synthesis.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because thiamine is not directly involved in the activity of other enzymes like pyruvate dehydrogenase or alpha-ketoglutarate dehydrogenase, although it is also a cofactor for these enzymes.
**Option B:** This option is incorrect because vitamin B6 (pyridoxine) is a cofactor for enzymes involved in amino acid metabolism, such as transaminases and decarboxylases, but not for transketolase.
**Option C:** This option is incorrect because vitamin B12 (cobalamin) is involved in the metabolism of fatty acids and amino acids, particularly in the synthesis of methionine, but it is not related to transketolase activity.
**Clinical Pearl / High-Yield Fact**
Thiamine deficiency can lead to a decrease in transketolase activity, which is a sensitive indicator of thiamine deficiency. This can be observed in patients with beriberi or Wernicke-Korsakoff syndrome, conditions associated with thiamine deficiency.
**Correct Answer:** D. Thiamine (Vitamin B1).