Radiation-induced inactivation of flavocytochrome b2 in dilute aqueous solution
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- 作者：Bhattacharya ; Debjani ; Saha ; Abhijit ; Mandal ; Parikshit C.
- 关键词：Radical species ; Michaelis-Menten kinetics ; Enzyme inactivation ; Flavocytochrome b2 ; (S. cerevisiae)
- 刊名：Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular Enzymology
- 出版年：1995
- 出版时间：July 3, 1995
- 年：1995
- 卷：1250
- 期：1
- 页码：1-8
- 全文大小：692 K
文摘
Effect of gamma radiation on flavocytochrome b2 in dilute aqueous solution was studied. A study of the effect of the radiolytically produced inorganic free-radical anions such as I
−2, Br−2 and (SCN)−2 on the enzyme activity indicates the involvement of cysteine and tyrosine residues in the catalytic activity of flavocytochrome b2. The changes in kinetic parameters, i.e., Michaelis-Menten constant Km and maximal velocity Vmax, due to irradiation under different conditions suggest that radiation induced enzyme inactivation is the result of destruction of active-site residues as well as modification of the substrate binding site. Fluorescence studies of unirradiated and irradiated enzyme reveal that FMN (flavin mononucleotide) is inaccessible to water radicals.
−2, Br−2 and (SCN)−2 on the enzyme activity indicates the involvement of cysteine and tyrosine residues in the catalytic activity of flavocytochrome b2. The changes in kinetic parameters, i.e., Michaelis-Menten constant Km and maximal velocity Vmax, due to irradiation under different conditions suggest that radiation induced enzyme inactivation is the result of destruction of active-site residues as well as modification of the substrate binding site. Fluorescence studies of unirradiated and irradiated enzyme reveal that FMN (flavin mononucleotide) is inaccessible to water radicals.