Thiamine deficiency is best detected by estimating the activity of -

Ans. is 'a' i.e., Transketolase* Thiamine is a water soluble vitamin* Structurally, thiamine is aminopyrimidine and a thiazole ring linked by a methylene bridge* Thiamine's coenzyme form is Thiamine Pyrophosphate (TPP) or Thiamine diphosphate* TPP acts as a coenzyme for:# Oxidative decarboxylation reactions* Pyruvate Dehydrogenase* a ketoglutarate dehydrogenase* Branched chain ketoacid dehydrogenase# Transketolase of HMP shunt* Transketolase is an enzyme, which transfers 2 carbon atoms from a pentose Xylulose 5 phosphate to another pentose Ribose 5 phosphate to form a heptose Sedoheptulose 7 phosphate and Glyceraldehyde 3 phosphate.* As transketolase requires Thiamine Pyrophosphate, thiamine deficiency can be detected by estimating erythrocyte transketolase activity* More than detecting low transketolase activity, proving that thiamine supplementation increases transketolase activity is found to be more diagnostic:# If the increase in Transketolase activity, after addition of thiamine, is between 0 and 15%, the thiamine status is normal# If the increase in Transketolase activity, after addition of thiamine, is between 15 and 25%, it is mild deficiency.# If the increase in Transketolase activity, after addition of thiamine, is more than 25%, it is severe deficiency.