The discovery that only the E1 subunit of the PDH complex has lower than normal activity has led you and the medical examiner to assay the concentrations of several key vitamins in various tissues. Assay results Riboflavin and niacin levels are at the low end of the normal range. Thiamine levels are nearly undetectable. Lipoic acid and pantothenic acid levels are at the low end of the normal range. The PDH complex requires the cosubstrate CoA as it converts pyruvate to acetyl CoA. What other cofactors or cosubstrates does the pyruvate dehydrogenase complex require to function