title: Radiation-induced inactivation of flavocytochrome b2 in dilute aqueous solution.
abstract: 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 I2.-, Br2.- 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.
authors.affiliation: Nuclear Chemistry Division, Saha Institute of Nuclear Physics, Calcutta, India.
authors.forename: D
authors.initials: D
authors.lastname: Bhattacharya
authors.forename: A
authors.initials: A
authors.lastname: Saha
authors.forename: P C
authors.initials: PC
authors.lastname: Mandal
mesh_terms: D001965:Bromides; D004789:Enzyme Activation / Q000528:radiation effects; D005609:Free Radicals; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects*; D042844:L-Lactate Dehydrogenase (Cytochrome); D017680:Potassium Compounds; D011193:Potassium Iodide; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D012996:Solutions; D013050:Spectrometry, Fluorescence; D013861:Thiocyanates; D014867:Water
chemical_list: D001965:Bromides; D005609:Free Radicals; D017680:Potassium Compounds; D012996:Solutions; D013861:Thiocyanates; D014867:Water; D011193:Potassium Iodide; D007770:L-Lactate Dehydrogenase; D042844:L-Lactate Dehydrogenase (Cytochrome); C039004:potassium bromide; C009941:potassium thiocyanate