(CELLG5 Method)

The CELLG5 assay reagent for the measurement of 
endo-cellulase (endo-1,4-β-glucanase) contains two components; 
1) 4,6-O-(3-Ketobutylidene)-4-nitrophenyl-β-D-cellopentaoside (BPNPG5) and 2) thermostable β-glucosidase. The ketone blocking group prevents any hydrolytic action by the 
β-glucosidase on BPNPG5.  Incubation with an endo-cellulase generates a non-blocked colourimetric oligosaccharide that is rapidly hydrolysed by the ancillary β-glucosidase. The rate of formation of 4-nitrophenol is therefore directly related to the hydrolysis of BPNPG5 by the endo-cellulase. The reaction is terminated and the phenolate colour is developed on addition of Tris buffer solution (pH 9.0).
The CELLG5 assay represents a huge step forward in the methodology for the measurement of cellulase that traditionally relied on substrates such as CM-cellulose, Avicel, cellooligosaccharides, filter paper or dyed polysaccharides including CMC Congo red or cellulose azure.