Sakamoto N, de Atauri P, Cascante M
Department of Biochemistry and Molecular Biology, Faculty of Chemistry, University of Barcelona, Spain.
Biosystems. 1998 Mar;45(3):221-35. doi: 10.1016/s0303-2647(98)00011-2.
An analysis of the effects of external and internal metabolites on the steady-state behavior of linear pathways comprising a sequence of three Michaelis-Menten-type reactions with and without a simple feedback inhibition (i.e. an interaction of an internal metabolite with the pathway) is performed with respect to the transit time tau by its formulation as rectangular-hyperbolic functions of the flux J, instead of direct expressions in terms of the external metabolite concentrations. For a given concentration of the external metabolite M1 (substrate of the pathway) or M4 (product of the pathway), the flux J has a lower value in the pathway with feedback inhibition than in the pathway without feedback inhibition. With variation in the M1 concentration the transit time tau shows a concave relationship with the flux J which is virtually identical for both pathways, yielding a minimum at a certain value of J. With variation in the M4 concentration the transit time tau monotonously decreases with higher value of J, and for a given value of J the feedback inhibition allows a lower transit time. This effect is enhanced with stronger feedback inhibition, and is in turn greatly reduced with higher values of total concentration and rate constants for the first enzyme in the pathway.
通过将转运时间τ表示为通量J的矩形双曲线函数，而不是直接用外部代谢物浓度的表达式，对外部和内部代谢物对包含三个米氏型反应序列且有无简单反馈抑制（即内部代谢物与途径的相互作用）的线性途径稳态行为的影响进行了分析。对于给定浓度的外部代谢物M1（途径的底物）或M4（途径的产物），具有反馈抑制的途径中的通量J值低于无反馈抑制的途径。随着M1浓度的变化，转运时间τ与通量J呈现出凹形关系，这在两条途径中几乎相同，在特定的J值处出现最小值。随着M4浓度的变化，转运时间τ随着J值的升高而单调减少，并且对于给定的J值，反馈抑制允许更低的转运时间。这种效应随着更强的反馈抑制而增强，而随着途径中第一种酶的总浓度和速率常数的升高而大大降低。
