Are cellulases slow? Kinetic and thermodynamic limitations for enzymatic breakdown of cellulose

Peter Westh*, Jeppe Kari, Silke Badino, Trine Sørensen, Stefan Christensen, Nanna Røjel, Corinna Schiano-di-Cola, Kim Borch

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Cellulases are of paramount interest for upcoming biorefineries that utilize residue from agriculture and forestry to produce sustainable fuels and chemicals. Specifically, cellulases are used for the conversion of recalcitrant plant biomass to fermentable sugars in a so-called saccharification process. The vast literature on enzymatic saccharification frequently refers to low catalytic rates of cellulases as a main bottleneck for industrial implementation, but such statements are rarely supported by kinetic or thermodynamic considerations. In this perspective, we first discuss activation barriers and equilibrium conditions for the hydrolysis of cellulose and how these parameters influence enzymatic turnover. Next, we propose a simple framework for kinetic description of cellulolytic enzyme reactions and show how this can pave the way for comparative biochemical analyses of cellulases acting on their native, insoluble substrate. This latter analysis emphasizes that cellulases are characterized by extraordinarily low off-rate constants, while other kinetic parameters including specificity constants and rate constants for association and bond cleavage are quite like parameters reported for related enzymes acting on soluble substrates.
Original languageEnglish
Article number100128
JournalBBA Advances
Volume7
Number of pages12
ISSN2667-1603
DOIs
Publication statusPublished - 2025

Keywords

  • Thermodynamic stability of cellulose
  • Kinetic stability of cellulose
  • Recalcitrance
  • Cellulase kinetics
  • Interfacial enzyme kinetics
  • Rate constants
  • Attack site density
  • Thermoactivation
  • Enzyme engineering

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