Kinetics of inactivation of phytase (phy A) during modification of histidine residue by IAA and DEP.
Chemical probing of histidine residues using specific modifiers, iodoacetic acid (IAA) and diethylpyrocarbonate (DEP) resulted in the inactivation of phytase (phy A). The kinetic theory of the substrate reaction during the modification of enzyme activity was applied to a study of the kinetics of the course of inactivation of phytase by IAA and DEP. The results suggested that histidine residues are involved in the active site of the enzyme. They also indicated that inactivation of the enzyme by IAA was via a complexing type inhibition, while the inhibition by DEP reaction involved a conformational change step before inactivation. The dissociation constant of the enzyme-inhibitor complex of IAA, the constant of the conformational change of DEP and the microscopic rate constants of two inhibitors were obtained.
Wang
Xiao-Yun
XY
College of Life Science, Shandong Agricultural University, Shandong Taian 271018, People's Republic of China. xyunwang@sdau.edu.cn
Sun
Ming-Lv
ML
Zhao
Dong-Min
DM
Wang
Min
M
D010832:6-Phytase / Q000737:chemistry* / Q000378:metabolism*; D001230:Aspergillus / Q000201:enzymology; D004047:Diethyl Pyrocarbonate / Q000737:chemistry* / Q000494:pharmacology; D006639:Histidine / Q000737:chemistry / Q000378:metabolism*; D019807:Iodoacetic Acid / Q000737:chemistry* / Q000494:pharmacology; D007700:Kinetics; D011489:Protein Denaturation / Q000187:drug effects
D006639:Histidine; D010832:6-Phytase; D004047:Diethyl Pyrocarbonate; D019807:Iodoacetic Acid