<prompt> Proper functioning of Kreb cycle does not occur with deficiency ofThiamineRiboflavinVitamin EVit K  <response>: Biological active form is Thiamine pyrophosphate TPP. Acts as a coenzyme in several metabolic reactions. Acts as coenzyme to the enzyme pyruvate dehydrogenase complex PDH which conves pyruvic acid to acetyl-CoA oxidative decarboxylation Pyruvate PDH TPP Acetyl-CoA Similarly acts as a coenzyme to a-oxoglutarate dehydrogenase complex and conves a-oxoglutarate to succinyl-CoA oxidative decarboxylation. a-oxoglutarate dehydrogenase a-Oxoglutarate TPP Succinyl-CoARef: MN Chatterjea Textbook of Medical Biochemistry, 6th Edition, Page no: 178 