Substrate structural mapping suggests that the catalytic site of cellobiose dehydrogenase from Phanerochaete chrysosporium forms a narrow cave with two hexose binding subsites. Kinetic data also show that beta-di or oligosaccharides are favored electron donors with respect to both KM and kcat. Surprisingly, thiocellobiose showed an even higher kcat than cellobiose, although the KM value was somewhat higher. The CDH was purified using an updated protocol.