title: Humicola insolens cellobiose dehydrogenase: cloning, redox chemistry, and "logic gate"-like dual functionality.
abstract: 1Cellobiose dehydrogenase is a hemoflavoenzyme that catalyzes the sequential electron-transfer from an electron-donating substrate (e.g. cellobiose) to a flavin center, then to an electron-accepting substrate (e.g. quinone) either directly or via a heme center after an internal electron-transfer from the flavin to heme. We cloned the dehydrogenase from Humicola insolens, which encodes a protein of 761 amino acid residues containing an N-terminal heme domain and a C-terminal flavin domain, and studied how the catalyzed electron transfers are regulated. Based on the correlation between the rate and redox potential, we demonstrated that with a reduced flavin center, the enzyme, as a reductase, could export electron from its heme center by a "outer-sphere" mechanism. With the "resting" flavin center, however, the enzyme could have a peroxidase-like function and import electron to its heme center after a peroxidative activation. The dual functionality of its heme center makes the enzyme a molecular "logic gate", in which the electron flow through the heme center can be switched in direction by the redox state of the coupled flavin center.
authors.affiliation: Novozymes Biotech, Inc., 1445 Drew Avenue, 95616, Davis, CA, USA
authors.forename: F
authors.initials: F
authors.lastname: Xu
authors.forename: E J.
authors.initials: EJ
authors.lastname: Golightly
authors.forename: K R.
authors.initials: KR
authors.lastname: Duke
authors.forename: S F.
authors.initials: SF
authors.lastname: Lassen
authors.forename: B
authors.initials: B
authors.lastname: Knusen
authors.forename: S
authors.initials: S
authors.lastname: Christensen
authors.forename: K M.
authors.initials: KM
authors.lastname: Brown
authors.forename: S H.
authors.initials: SH
authors.lastname: Brown
authors.forename: M
authors.initials: M
authors.lastname: Schülein