Relative activity of CEL6A molecules. Purified CEL6A and purified CEL6A-His6 were compared in two cellulose hydrolysis activity assays. CEL6A and CEL6A-His6 exhibited similar activity in PASC hydrolysis (top graph). PASC activity was determined by measurement of reducing sugars by PAHBAH following 1-hr incubation at 50°C in 1% (wt/wt) PASC. However, CEL6A-His6 activity was compromised, compared to native CEL6A, in hydrolysis of dilute acid pretreated corn stover (bottom graph), PCS miniaturized assay.