JBC, Vol. 252, Issue 22, 7919-7922, Nov, 1977
Kinetics of soluble and collagen-bound aspartate aminotransferase: diffusional effects with a two-substrate enzymatic reaction
J. M. Engasser
The kinetic properties of aspartate aminotransferase covalently bound to
collagen are compared to those of the free enzyme. In the bound state, the
enzyme exhibits a greater affinity for glutamate, but a lower affinity for
oxalacetate. In order to assess precisely the contribution of diffusional
limitations on the heterogeneous enzyme kinetics, a simple modeling of
diffusional effects on a two-substrate enzymatic reaction is developed.
According to this quantitative analysis, diffusional limitations for
oxalacetate alone account for the increased and decreased enzyme affinities
toward its two substrates. Consequently, coupling of the enzyme to collagen
does not significantly affect its intrinsic kinetic properties.