Affinity chromatography of extracellular cellulase from chaetomium cellulolyticum

Cellobiose dehydrogenase-an extracellular fungal flavocytochrome

Wood-degrading fungi, including white-rot and soft-rot fungi as well as at least one brown-rot fungus, produce cellobiose dehydrogenase (CDH). CDH has generated recent interest because of its ability to facilitate the formation of free radicals and because it makes a nice model to study intraprotein electron transfer. While the physiological function of CDH is not known, a considerable portion of this review discusses the strength of the data dealing with individual hypotheses. New evidence dealing with proteolysis of CDH in relationship to the interaction of CDH with lignin and manganese peroxidases are discussed. Additionally, recent information dealing with the catalytic mechanism and reactivity of the individual domains of CDH is detailed.

Small-angle X-ray scattering studies on cellobiose dehydrogenase from Phanerochaete chrysosporium

Limited proteolysis of cellobiose dehydrogenase (CDH) from the white rot fungus Phanerochaete chrysosporium by papain cleaves the enzyme into two fragments containing flavin (FAD) and heme, respectively. Small-angle X-ray scattering (SAXS) was employed to investigate size and shape of intact CDH and of its fragments in solution. The largest dimension of CDH amounts to about 18 nm, whereas the corresponding quantity of each of the two fragments is only around 9 nm. CDH as well as its fragments appear to be of prolate shape, the cross-section of the FAD fragment (diameter 4.3 to 5.1 nm) being considerably larger than that of the heme fragment (diameter 3.3 nm). These findings suggest a collinear arrangement of the two domains in the CDH particle. Simulations based on the method of finite elements corroborate this structure model and furthermore suggest the existence of a possibly flexible linker between the two domains.