Effects of low intensity laser (632.8 nm) and ultraviolet radiation on spectral properties and functional activity of human ceruloplasmin

Photoinduced changes of human ceruloplasmin (hCp) under laser and ultraviolet (UV) radiation have been studied. A complex character of hCp spectral modifications points to a different degree of the protein molecule folding. After the influence of UV radiation (240-390 nm) in a dose range 906-4530 J/m2 the decrease of oxidase hCp activity was registered. These changes are thought to be connected with modification of the conformation of hCp active centre or copper reduction that was confirmed by the decrease of optical density at 610 nm. An inactivation constant (kf = 3.8 x 10(-4) 1/s) and a photoinactivation quantum yield (1.4 x 10(-4)) were calculated. Kinetic dependencies of o-phenilen-diamine oxidation by intact and UV-modified glycoprotein do not correspond to Michaelis-Menten equation. UV radiation in a dose range 151-4530 J/m2 induced increasing of ceruloplasmin superoxiddismutase activity. The influence of He-Ne laser radiation (1.3 mW; lambda = 632.8 nm, exposure time from 1 up to 30 min) leads to the raise of the hCp functional activity; superoxiddismutase activity changes more significantly. Possible photophysical and photochemical processes in hCp molecule, leading to photomodification and changes of protein functional activity have been represented on the scheme.