Riboflavin deficiency is assessed by

Riboflavin deficiency is assessed by Glutathione reductase. The two biologically active forms are flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), formed by the transfer of an adenosine monophosphate moiety from ATP to FMN (Figure 28.15). FMN and FAD are each capable of reversibly accepting two hydrogen atoms, forming FMNH2or FADH2. FMN and FAD are bound tightly--sometimes covalently--to flavoenzymes that catalyze the oxidation or reduction of a substrate. Riboflavin deficiency is not associated with a major human disease, although it frequently accompanies other vitamin deficiencies. Deficiency symptoms include dermatitis, cheilosis (fissuring at the corners of the mouth), and glossitis (the tongue appearing smooth and purplish). Reference: Lippincott Textbook of Biochemistry pg no. 380,381