JBC, Vol. 250, Issue 15, 5951-5959, Aug, 1975
Spectral properties of Co(II)- and Ni(II)-activated rabbit muscle pyruvate kinase
C. Y. Kwan, K. Erhard and R. C. Davis
Stoichiometry, kinetics, and optical properties of rabbit muscle pyruvate
kinase activated with Co(II), Ni(II), Mg(II), and Mn(II) were studied. The
stoichiometry of metal binding to enzyme was found to be 4 metal ions per
tetrameric enzyme for Co(II) and Ni(II) by carrying out circular dichroic
titrations. Cu(II) and Fe(II) were inactive. Ca(II) and Zn(II) were not
activating, and were inhibitory with respect to all of the active cations.
The temperature dependence of the optimal velocity is similar for all
activating metals. The pH rate profiles suggest that there are two classes
of enzyme activation by metal ions. Mg(II) and Mn(II) are quite similar to
each other while Co(II) and Ni(II) are different from them but similar to
each other. Absorption, natural, and magnetic CD in the visible region were
used to probe the environment of the activating divalent cation in Ni(II)-
and Co(II)-activated pyruvate kinase and their complexes with substrates
and inhibitors...