Catalytic subunit of fructose dehydrogenase, an enzyme that catalyzes the oxidation of D-fructose to produce 5-keto-D-fructose. a ubiquinone + keto-D-fructose = 5-dehydro-D-fructose + a ubiquinol Measured for the whole complex. Optimum pH is 4.0. Heterotrimer composed of FdhL, FdhS and FdhC. This enzyme is commonly used in a number of research projects to examine the electrochemical properties of enzyme-catalyzed electrode reactions, named bioelectrocatalysis. Available as a commercial product from Sigma Aldrich (catalog number F4892). Belongs to the GMC oxidoreductase family.