Studies on the Interaction of Substrate and Monovalent and Divalent Cations with Pyruvate Kinase^*

Pyruvate kinase: Activation by and catalytic role of the monovalent and divalent cations

“…~When reference is made to pyruvate kinase throughout the remainder of this review, we shall refer to Type M of rabbit muscle since the bulk of the monovalent and divalent cation studies were completed with this isozyme. When the binding of cations was investigated by difference spectroscopy in the presence of nonactivating (CH3) 4 N +, the K D for K + was 0.1 M (42). This value agrees with the kinetically determined dissociation constant for K + obtained by extrapolation to zero concentration of Mn +2.…”

“…This value agrees with the kinetically determined dissociation constant for K + obtained by extrapolation to zero concentration of Mn +2. At infinite concentration of Mn +2, the kinetically determined dissociation constant K D = 14 mM (42). This synergistic effect of the divalent cation on the binding of the monovalent cation has also been demonstrated withT1 + (48) and CH3NH3 + (43,49).…”

Tissue Distribution of Human Pyruvate Kinase Isozymes

“…Rabbit muscle PK can be dissociated into four subunits, but the whole molecule contains only two binding sites for each substrate (ADP and PEP) and for each activating cation (Mg++ and K+) [7,12,13]. Steinmetz and Deal suggest that the mole cule consists of two identical "protomers", each dissociable into two similar but not identical polypeptide chains.…”

Pyruvate Kinase Revisited

“…This provided important evidence for a direct participation on the catalytic events at the active site. Along this time, kinetic, UV difference spectroscopy, and EPR studies showed a synergistic effect in the binding of Mn 2ϩ and K ϩ to the enzyme (13,14). In NMR proton relaxation rate titration experiments, it was found that K ϩ raised the affinity of the enzyme for PEP and its analogs and that PEP and its analogs raised the affinity of the enzyme for K ϩ .…”