InterPro domain: IPR037458

L-Lactate dehydrogenase (L-LDH) Fcb2 from Saccharomyces cerevisiae and L-mandelate dehydrogenase (L-MDH) from Rhodotorula graminis are both flavocytochromes b2. L-LDH is a respiratory enzyme located in the intermembrane space of fungal mitochondria which catalyzes the oxidation of L-lactate to pyruvate. It is composed of 2 domains: a C-terminal flavin-binding domain, which includes the active site for lactate oxidation, and an N-terminal b2-cytochrome domain, required for efficient cytochrome c reduction. Despite their similarities these enzymes have distinct substrate specificities; L-LDH is unable to oxidize mandelate, whereas L-MDH is unable to oxidize lactate [ 1 , 2 ].

Fcb2 is composed of 2 domains: a C-terminal FMN-binding domain, which includes the active site for lacate oxidation, and an N-terminal b2-cytochrome domain, required for efficient cytochrome c reduction. Fcb2 is a homotetramer and contains two noncovalently bound cofactors, FMN and heme per subunit. This entry represents the FMN-binding domain [ 3 ].

1. Re-design of Saccharomyces cerevisiae flavocytochrome b2: introduction of L-mandelate dehydrogenase activity. Biochem. J. 333 ( Pt 1), 117-20
2. L-mandelate dehydrogenase from Rhodotorula graminis: comparisons with the L-lactate dehydrogenase (flavocytochrome b2) from Saccharomyces cerevisiae. Biochem. J. 290 ( Pt 1), 103-7
3. Crystallographic study of the recombinant flavin-binding domain of Baker's yeast flavocytochrome b(2): comparison with the intact wild-type enzyme. Biochemistry 41, 4264-72