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Stopped‐flow kinetic studies of the cellulase‐catalyzed conversion of cellulose to glucose
Author(s) -
Banerjee D. K.,
Laidler K. J.
Publication year - 1983
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.260251011
Subject(s) - cellulase , cellulose , substrate (aquarium) , chemistry , catalysis , activation energy , imidazole , kinetics , kinetic energy , enzyme kinetics , enzyme , mole , medicinal chemistry , stereochemistry , nuclear chemistry , active site , organic chemistry , biology , ecology , physics , quantum mechanics
The kinetics of the cellulase‐catalyzed conversion of soluble cellulose into glucose have been studied over a range of substrate concentrations and temperatures, and at pH values ranging from 4.75 to 7.0. Lineweaver‐Burk plots were linear and led to V = 6.2μ M /s and K m = 13.1 m M at pH 5.8 and 25.0°C. The pK values corresponding to the free enzyme are 4.8 and 6.8 and are consistent with carboxyl and imidazole groups as the active ionizing species. These pK values were little changed in the enzyme‐substrate intermediate that reacts in the ratedetermining step, suggesting that the ionizing groups are still free in this intermediate. The activation energy corresponding to V / K m is 80.6 kJ/mol, and that corresponding to V is 38.7 kJ/mol. The corresponding entropies of activation are 21 J K −1 mol −1 and –157 J K −1 mol −1 , respectively.