To better understand factors that hinder cellulose degradation by cellobiohydrolases, we characterized accessory enzymes that act on cellulose in combination with Trichoderma reesei Cel7A. These accessory enzymes include endo-1,4-beta-D-glucanase (Cel7B) from Trichoderma longibrachiatum and Cel6A, a cellobiohydrolase II. By measuring reducing end production in reactions between cellulose from Acetobacter and these enzymes, we found that  Cel7B acts with Cel7A in an additive manner while Cel6A acts with Cel7A in a synergistic manner.