Unfolding and inactivation of Ampullarium crossean beta-glucosidase during denaturation by guanidine hydrochloride.
Changes of activity and conformation of Ampullarium crossean beta-glucosidase in different concentrations of guanidine hydrochloride (GuHCl) have been studied by measuring the fluorescence spectra and its relative activity after denaturation. The fluorescence intensity of the enzyme decreased distinctly with increasing guanidine concentrations, the emission peaks appeared red shifted (from 338.4 to 350.8 nm), whereas a new fluorescence emission peak appeared near 310 nm. Changes in the conformation and catalytic activity of the enzyme were compared. A corresponding rapid decrease in catalytic activity of the enzyme was also observed. The extent of inactivation was greater than that of conformational changes, indicating that the active site of the enzyme is more flexible than the whole enzyme molecule. k(+0)>k(+0)' also showed that the enzyme was protected by substrate to a certain extent during guanidine denaturation.
Chen
Qing-Xi
QX
Department of Biology, School of Life Sciences, Xiamen University, PR China. chenqx@jiangxian.xmu.edu.cn
Zhang
Zhe
Z
Huang
Huang
H
Zhao
Fu-Kun
FK
Xu
Gen-Jun
GJ
D000818:Animals; D019791:Guanidine / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D011487:Protein Conformation / Q000187:drug effects; D011489:Protein Denaturation / Q000187:drug effects; D017510:Protein Folding; D012908:Snails / Q000201:enzymology*; D001617:beta-Glucosidase / Q000037:antagonists & inhibitors*
D001617:beta-Glucosidase; D019791:Guanidine