ABSTRACT
The state of tryptophan-containing sites is proved to be stable by intrinsic tryptophan fluorescence with pH 5-8, 7-9, and 6-9 in human, rabbit and bovine plasminogen molecules, respectively. With pH < 5.0 tryptophan-containing sites of human zymogen (in contrast to rabbit and bovine ones) undergo conformational transitions. With the shift of solution pH from 9 to 12 tryptophan-containing sites of human and rabbit plasminogens are partially disorganized, while tryptophanyls become more available for solvent. Tryptophan-containing sites of bovine plasminogen molecules are less mobile in structure during changes of solution pH.
Subject(s)
Plasminogen/chemistry , Tryptophan/chemistry , Animals , Cattle , Humans , Hydrogen-Ion Concentration , Rabbits , Solvents , Spectrometry, Fluorescence , Tryptophan/analysisABSTRACT
Human, rabbit and bovine plasminogens, having different sensitivity to streptokinase-activating action, differ, according to spectrophotometric titration, tryptophan fluorescence and circular dichroism spectroscopy, in the state of tyrosine and tryptophan residues, and in secondary and tertiary structures. Human plasminogen-streptokinase equimolar complex formation (according to gel chromatography) is accompanied by a differential ultraviolet spectrum. Difference spectroscopy is a convenient and adequate means of studying the formation of the said complexes. Streptokinase-human plasminogen complex formation is not hindered by partial substitution of water (20%) with ethanol or dimethylsulphoxide or by addition of 0.001 M sodium dodecylsulphate. The complex is not formed in 6 M urea, in solution, at pH less than 2.0 or approximately 12.0-13.0, or with bovine plasminogen. Circular dichroism and tryptophan fluorescence spectral pattern changes during streptokinase-plasminogen complex formation enable us to conclude that streptokinase secondary and tertiary structures undergo certain rearrangements in the framework of the complex, while tryptophan-containing sites of the molecule are not drastically changed. The data obtained enable us to presuppose formation of streptokinase-rabbit plasminogen complexes which differ from human plasminogen complexes with streptokinase.
Subject(s)
Plasminogen/chemistry , Streptokinase/metabolism , Animals , Cattle , Circular Dichroism , Enzyme Activation , Humans , Hydrogen-Ion Concentration , Plasminogen/metabolism , Protein Conformation , Rabbits , Tryptophan/chemistry , Tyrosine/chemistryABSTRACT
A study was made of the effect of a single exposure of rats to 0.4 Gy X-radiation on the content of pyridoxal phosphate and pyridoxamine phosphate in gray and white brain substances and liver. At the same time changes were noted in the activity of pyridoxal kinase in the tissues under study.
