Premium
Cycloamylose Glucanotransferase‐catalyzed Cyclisation for a Substrate Maltose. Modification with N‐Bromosuccimide on the Tryptophan Residues
Author(s) -
Ohnishi Masatake,
Azuma Toru,
Kubota Michio
Publication year - 1994
Publication title -
starch ‐ stärke
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.62
H-Index - 82
eISSN - 1521-379X
pISSN - 0038-9056
DOI - 10.1002/star.19940460710
Subject(s) - disproportionation , chemistry , tryptophan , substrate (aquarium) , maltose , residue (chemistry) , catalysis , hydrolysis , michaelis–menten kinetics , stereochemistry , organic chemistry , enzyme , biochemistry , enzyme assay , amino acid , biology , ecology
Cycloamylose glucanotransferase (CGTase, EC 2.4.1.19) from Bacillus stearothermophilus was found to catalyze the production of cyclomalto‐oligosaccharides from maltose (G 2 ) as a substrate. This synthesis reaction, called “cyclisation” is one of the four CGTase‐catalyzed reactions: disproportionation, coupling, hydrolysis, and cyclisation. On the reaction time‐course observed by using the fluorescence method, a lag‐phase was found prior to the production of cyclomalto‐oligosaccharides. The lag‐time may be referred to a reaction “disproportionation”. Based on the linear portion of the reaction curves, the kinetic parameters, the Michaelis constant Km and the molar activity k 0 , were evaluated for the G 2 cyclisation. Modification of tryptophan residues with N‐bromosuccinimide gives not so much effect on the Km and k 0 values for cyclisation. However, an effect was found on the lag‐time, suggesting that the Trp residue (Trp97) carries an essential role in the disproportionation process.