4.6 Article

pH profiles of cellulases depend on the substrate and architecture of the binding region

Journal

BIOTECHNOLOGY AND BIOENGINEERING
Volume 117, Issue 2, Pages 382-391

Publisher

WILEY
DOI: 10.1002/bit.27206

Keywords

cellobiohydrolase; cellulose; endoglucanase; pH; temperature

Funding

  1. Carlsbergfondet [2013-01-0208]
  2. Novo Nordisk Foundation [NNF15OC0016606, NNFSA170028392]
  3. Innovation Fund Denmark [5150-00020B]

Ask authors/readers for more resources

Understanding the pH effect of cellulolytic enzymes is of great technological importance. In this study, we have examined the influence of pH on activity and stability for central cellulases (Cel7A, Cel7B, Cel6A from Trichoderma reesei, and Cel7A from Rasamsonia emersonii). We systematically changed pH from 2 to 7, temperature from 20 degrees C to 70 degrees C, and used both soluble (4-nitrophenyl beta-d-lactopyranoside [pNPL]) and insoluble (Avicel) substrates at different concentrations. Collective interpretation of these data provided new insights. An unusual tolerance to acidic conditions was observed for both investigated Cel7As, but only on real insoluble cellulose. In contrast, pH profiles on pNPL were bell-shaped with a strong loss of activity both above and below the optimal pH for all four enzymes. On a practical level, these observations call for the caution of the common practice of using soluble substrates for the general characterization of pH effects on cellulase activity. Kinetic modeling of the experimental data suggested that the nucleophile of Cel7A experiences a strong downward shift in pK(a) upon complexation with an insoluble substrate. This shift was less pronounced for Cel7B, Cel6A, and for Cel7A acting on the soluble substrate, and we hypothesize that these differences are related to the accessibility of water to the binding region of the Michaelis complex.

Authors

I am an author on this paper
Click your name to claim this paper and add it to your profile.

Reviews

Primary Rating

4.6
Not enough ratings

Secondary Ratings

Novelty
-
Significance
-
Scientific rigor
-
Rate this paper

Recommended

No Data Available
No Data Available