Coenzymes Derived from Vitamins

A 42-year-old male construction worker from rural Maharashtra presents with progressive weakness, numbness in his feet, and difficulty walking for the past 3 months. On examination, he has a stocking-glove distribution of sensory loss, diminished deep tendon reflexes, and mild ataxia. His diet consists mainly of polished rice and minimal protein intake. Blood investigations show macrocytic anemia (Hb 9.2 g/dL, MCV 108 fL), and serum B12 level is 180 pg/mL (normal >200). Methylmalonic acid and homocysteine levels are elevated. Which coenzyme deficiency is primarily responsible for his neurological manifestations?

A 38-year-old woman from Delhi presents with a 2-month history of progressive fatigue, dyspnea on exertion, and recurrent mouth ulcers. On examination, she has glossitis, angular cheilitis, and mild hepatomegaly. Her diet is predominantly vegetarian with minimal intake of whole grains and legumes. Blood tests show: Hb 9.8 g/dL, MCV 72 fL (microcytic), serum folate 2.1 ng/mL (normal >5.4), and serum B12 450 pg/mL (normal). Serum homocysteine is elevated at 18 μmol/L. Which coenzyme deficiency explains both her mucosal manifestations and the elevated homocysteine despite normal B12 levels?

Which vitamin B derivative serves as the prosthetic group for pyruvate dehydrogenase complex and α-ketoglutarate dehydrogenase complex?

Methylmalonyl-CoA mutase requires which vitamin B₁₂-derived coenzyme for its catalytic activity?