ABSTRACT

The story of flavocytochrome b2 begins in 1928, when F. Bernheim prepared a baker's yeast extract which oxidized methylene blue at the expense of lactate, glycolate, and a-hydroxybutyrate. When flavocytochrome b2 functions in the transhydrogenation mode in the presence of a tritiated hydroxy acid, it catalyzes an intermolecular tritium transfer from C2 of the hydroxy substrate to C2 of the ketosubstrate. Site-directed mutagenesis is now available as an additional tool in the study of structure function relationships in flavocytochrome b2. The proposed N-terminal localization of the flavocytochrome b2 signal sequence was demonstrated when the protein gene was cloned346 and sequenced. The interaction of nitroethane and ethanenitronate with flavocytochrome b2 was studied in the hope of obtaining evidence in favor of the existence of an intermediate covalent adduct in catalysis. A flavocytochrome b2 from another yeast, Hansenula anomala, has been well characterized.