Formate dehydrogenase (acceptor) (EC 1.1.99.33, FDHH, FDH-H, FDH-O, formate dehydrogenase H, formate dehydrogenase O) is an enzyme with systematic name formate:acceptor oxidoreductase. This enzyme catalyses the following chemical reaction Formate dehydrogenase (acceptor) (EC 1.1.99.33, FDHH, FDH-H, FDH-O, formate dehydrogenase H, formate dehydrogenase O) is an enzyme with systematic name formate:acceptor oxidoreductase. This enzyme catalyses the following chemical reaction Formate dehydrogenase H is a cytoplasmic enzyme that oxidizes formate without oxygen transfer] transferring electrons to a hydrogenase.