# Reporter Group-Labeled Synthetic Cellulose: Structural Characterization and Utilization in Mapping the Cellulose Chain-Cleavage Modes of Cellulases

## TL;DR

Scientists created labeled cellulose to study how enzymes break down cellulose, revealing insights into enzyme activity on crystalline structures.

## Contribution

Development of reporter group-labeled synthetic cellulose to map cellulase chain-cleavage modes on crystalline substrates.

## Key findings

- Synthetic cellulose-pNP forms nanoscale sheet-like assemblies with thickness ~4 nm.
- Hydrolase systems prefer processive chain cleavage from chain ends, influenced by local nanoscale structure.
- T. reesei Cel7A preferentially attacks sheet edges, with degradation efficiency dependent on structure.

## Abstract

Iterative β-1,4-glucosylation of p-nitrophenyl
(pNP)-β-cellobioside
by cellodextrin phosphorylase was applied to synthesize reducing-end
reporter group-labeled cellooligosaccharides (average degree of polymerization,
DP: ∼5.7; DP range: 4–10) which, upon self-assembly
in solution, precipitate as a cellulose allomorph II crystalline material.
Atomic force microscopy revealed that the synthetic cellulose-pNP
forms nanoscale sheet-like assemblies, with thickness ∼4 nm.
The labeled cellulose was used to characterize the chain cleavage
specificities of cellulose-degrading enzymes. Reactions were monitored
by the release of soluble products as well as the change in oligosaccharide
composition of the residual solid material, measured by mass spectrometry.
The products formed by hydrolase systems (Trichoderma
reesei cellulases; Clostridium thermocellum cellulosome) are controlled by processive chain cleavages from the
chain ends. Atomic force microscopy shows that T. reesei Cel7A preferentially attacked sheet edges, with degradation efficiency
and directionality dependent on local nanoscale structure. Collectively,
we show synthesis of reporter group-labeled cellulose for probing
enzymatic chain depolymerization activity on a crystalline solid substrate.