Combined effects of diffusional hindrances, electrostatic repulsion and product inhibition on the kinetic properties of a bound acid phosphatase

FEBS Letters

Hervagault, Jean-François¹  Thiébart-Fassy, Isabelle¹ 

[1] Unité de Recherche Associée no 1442 du Centre National de la Recherche Scientifique, Université de Compiègne, BP 649, 60206 Compiègne Cedex, France

关键词: Soybean phosphatase;    Plant cell wall;    Semi-natural membrane;    Diffusion—partition reaction;    Kinetic model;    Phosphomonoester;   

DOI  :  10.1016/0014-5793(93)81688-V

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The kinetic properties of a soybean cell wall phosphatase were studied and compared under different environmental conditions. The native enzyme isolated from the wall exhibits classical Michaelis Menten kinetics. When buried into the cell wall, its natural environment, the enzyme mimics an apparent negative cooperativity. This deviation from hyperbolic dependence of the activity vs. the substrate concentration may result from an heterogeneous distribution of the enzyme molecules between the surface and the inside of the wall, where an electrostatic partition effect takes place. Cell wall fragments compacted on a Millipore-type membrane allow the study of the dual effects of diffusional hindrances and electrostatic interactions on the global kinetic behavior. By increasing the ionic strength, partition effects can be suppressed and therefore diffusional effects alone can be taken into account. On the one hand, diffusion and partition act individually and synergetically to decrease the apparent global affinity of phosphatase with respect to glucose 6-phosphate. On the other hand, product inhibition by inorganic phosphate is subjected to dual effects from diffusion through accumulation and partition through repulsion. A simple diffusion—partition reaction model accounts qualitatively and quantitatively for the experimental observations.

【 授权许可】

Unknown