I. Park et Dh. Ives, KINETIC MECHANISM AND END-PRODUCT REGULATION OF DEOXYGUANOSINE KINASEFROM BEEF-LIVER MITOCHONDRIA, Journal of Biochemistry, 117(5), 1995, pp. 1058-1061
Initial-rate kinetic measurements with the affinity purified 8-deoxygu
anosine (dGuo) kinase from beef liver mitochondria yielded reciprocal
plots which converged on the abscissa, with either dGuo or ATP as the
varied substrate, The limiting K-m, for dGuo was 4.7 mu M, and that fo
r ATP was 780 mu M. One product, dGMP, was competitive with both subst
rates, while the other, ADP, was competitive with ATP and non-competit
ive with dGuo. Qualitatively identical results were obtained with an a
lternative substrate, dTTP, and with alternative product inhibitors, d
IMP and dTDP. These results are consistent with a random Bi Bi kinetic
mechanism, judging from the formation of a dead-end complex of the en
zyme, dGuo and ADP, dGTP competes very strongly with ATP (K-1 = 0.03 m
u M), but is non-competitive towards dGuo. The more weakly-bound dGDP
is competitive with both substrates.