[Conformation of adenosine deaminase in complexes with inhibitors: application of selective quenching of fluorescence emission].

The effect of inhibitors, 1-deazaadenosine (1-dAdo) and erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA), on the conformation of adenosine deaminase was studied using the method of selective quenching of fluorescence emission by acrylamide, I- and Cs+. Both in free adenosine deaminase and in its complexes with the inhibitors, the wavelength maxima and half-width of the emission characterize the environment of fluorescing tryptophan residues in adenosine deaminase as weak polar with limited access to solvent. The formation of complexes with the ground state inhibitors used did not quench or change the main emission characteristics of tryptophan fluorescence in adenosine deaminase.

[The role of tryptophan in appearance of adenosine deaminase activity].

Chemical modification of tryptophan residues with N-bromosuccinimide and their photooxidation in the presence of trichloroethanol inhibited the activity of adenosine deaminase purified from gray and white matter of calf brain. Only two of six modified residues are important for enzyme activity. Preliminary kinetic data indicate that these essential tryptophan residues are adjacent to the substrate-binding site of the enzyme.

[Isolation, purification, and comparative study of the properties of adenosine deaminase from five regions of the cattle brain].

Adenosine deaminase from the white and gray matter of the large hemispheres, cerebellum, medulla oblongata and pituitary anterior lobe has been isolated and purified. The pH optimum, Km, molecular mass, yield and specific activities for all the enzyme preparations have been determined. Gel filtration and electrophoresis data point to the heterogeneity of the enzyme.