Allosteric character of the inhibition of @entity35 -muscle hexokinase B by XXXX .

@entity35 @entity857 @entity413 @entity855 @entity3776
We previously provided evidence from isotope-exchange measurements under non-equilibrium conditions that hexokinase B from @entity35 muscle follows a compulsory-order mechanism with @entity413 binding before @entity855 , and with both @entity3776 and @entity855 capable of binding allosterically [Gregoriou, M., Trayer, I. P. _ Cornish-Bowden, A. (1983) Eur. J. Biochem. 134, 283-288]. We have now re-examined this work in the light of recent criticisms [Ganson, N. J. _ Fromm, H. J. (1985) J. Biol. Chem. 260, 12099-12105]. There is no difficulty in obtaining valid estimates of initial rates of isotope exchange when the equilibrium constant is unfavourable, if one uses highly radioactive reactants and low enzyme concentrations, as we did in the experiments we reported previously. However, our earlier suggestion that @entity857 can be released within the inhibitory pathway, which was made for the sake of consistency with the catalytic pathway rather than because of any compelling experimental evidence, must be revised to avoid predicting that the rate must be zero in the absence of @entity857 . Although our mechanism admits the possibility of substrate inhibition by @entity855 , calculations show that there is no need for this to be observable under ordinary conditions. Indeed, with plausible values assumed for the kinetic constants one can calculate theoretical behaviour according to our model that closely resembles the experimental inhibition experiments that have been claimed as evidence against it.
