VPY-0055
QUESTION
The activity of which enzyme below in the HMP shunt would be affected by thiamin deficiency?
OPTIONS
(A) Glucose 6-phosphate dehydrogenase
(B) 6-phosphogluconate dehydrogenase
(C) Transketolase
(D) Transaldolase
ANSWER
(C) Transketolase
EXPLANATION
Transketolase is a thiamine-dependent enzyme involved in the non-oxidative phase of the hexose monophosphate (HMP) shunt, also known as the pentose phosphate pathway. It requires thiamine pyrophosphate (TPP), the biologically active form of vitamin B1, as an essential coenzyme. Thiamine deficiency reduces TPP availability, thereby decreasing transketolase activity. In contrast, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and transaldolase do not require thiamine as a coenzyme.