Open AccessCobalt Bovine Superoxide Dismutase
Author(s) -
CALABRESE Lilia,
COCCO Dina,
MORPURGO Laura,
MONDOVÌ Bruno,
ROTILIO Giuseppe
Publication year - 1976
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1976.tb10324.x
Subject(s) - chemistry , copper , cobalt , chromophore , copper protein , electron paramagnetic resonance , azurin , inorganic chemistry , cyanide , superoxide dismutase , zinc , histidine , photochemistry , reactivity (psychology) , hemocyanin , enzyme , organic chemistry , nuclear magnetic resonance , medicine , physics , alternative medicine , pathology , antigen , biology , genetics
1 The reactivity of the zinc site of bovine superoxide dismutase has been probed by observing optical and electron paramagnetic resonance changes, under several conditions, of the Co(II)‐substituted protein. 2 Only in the absence of copper are the optical and electron paramagnetic resonance spectra of the cobalt chromophore appreciably affected by alkaline pH or by cyanide. With both reagents the reaction with the copper‐containing protein appears to involve the water molecule bound to the copper and does not affect the magnetic coupling between copper and cobalt. 3 The reaction of cyanide with the copper‐free Co(II) protein leads to a slow detachment of cobalt from the protein as pentacyanocobalt. An oxygen adduct forms in air, analogous to that described in Co(II)carbonic anhydrase (Haffner, P. H. and Coleman, J. E. (1975) J. Biol. Chem. 250, 996–1005.) 4 Acid titration modifies the Co(II) spectra in the same way in the Cu‐containing and in the Cu‐free protein and brings about uncoupling of the Co(II)‐Cu(II) system. Protonation of histidine‐61 on the zinc facing nitrogen is suggested. 5 H 2 O 2 modifies the cobalt chromophore only in the presence of copper. Magnetic coupling between Cu(II) and Co(II) seems to be still present after H 2 O 2 inactivation of the enzyme.