M. Fukumura et al., PROCESS OF THERMAL-DENATURATION OF XYLANASE (XYNB) FROM CLOSTRIDIUM-STERCORARIUM F9, Bioscience, biotechnology, and biochemistry, 59(1), 1995, pp. 47-50
The thermal denaturation process of Clostridium stercorarium F-9 xylan
ase (XynB) was studied by monitoring remaining activity and recovered
activity of the enzyme. At pH 5.5, aggregation occurred rapidly after
the thermal denaturation initiated. The aggregated protein could be di
ssolved in 8 M urea solution, and the enzyme activity was recovered by
diluting the urea. The extent of the recovered activity was gradually
decreased with two phases as the reaction time of the thermal denatur
ation became longer. These results suggested the thermal denaturation
process to be as follows: [GRAPHICS] where N is the native state of th
e enzyme; D1 is the denatured state of the enzyme that is formed rapid
ly after the reaction started and can be renatured by the urea treatme
nt, and D2 and D3 are the denatured states of the enzyme that cannot b
e renatured even by the urea treatment. The rate constants were k(1) >
9.2, k(2) = 0.33, and k(2) = 0.57, and k(3) = 0.13 (in min(-1) unit).