TY - JOUR
T1 - The collisional limit
T2 - an important consideration for membrane-associated enzymes and receptors
AU - Abbott, A. J.
AU - Nelsestuen, G. L.
PY - 1988
Y1 - 1988
N2 - Because of the proximity of many bound receptors or enzymes, a membrane surface may become uniformly reactive so that every collision between a ligand and the membrane particle results in a binding or catalytic event. At this limit (the collisional limit), the reaction rate depends on membrane particle (cell) concentration and is independent of receptor concentration. Many receptor systems display properties that satisfy the requirements of a collisionally limited reaction. These include the presence of many receptors per cell. The filling of only a few of these receptors often generates the maximum cellular response, and the remaining receptors have been referred to as spare receptors. However, many receptors are needed to produce the collisional limit, and spare receptors may represent nature's evolution toward a reaction that provides the maximum rate as well as the maximum sensitivity to a ligand. Since receptors or enzymes provided on small membrane fragments will not function at the collisional limit, properties of reconstituted enzymes or receptors may not be extrapolated to the physiological situation. The use of normal bimolecular kinetic or equilibrium equations is inappropriate for reactions limited by collision and can give unusual results that lead to inappropriate conclusions. Determination of whether the collisional limit applies to a membrane-bound system is important for understanding its properties and those of the physiological circumstance.
AB - Because of the proximity of many bound receptors or enzymes, a membrane surface may become uniformly reactive so that every collision between a ligand and the membrane particle results in a binding or catalytic event. At this limit (the collisional limit), the reaction rate depends on membrane particle (cell) concentration and is independent of receptor concentration. Many receptor systems display properties that satisfy the requirements of a collisionally limited reaction. These include the presence of many receptors per cell. The filling of only a few of these receptors often generates the maximum cellular response, and the remaining receptors have been referred to as spare receptors. However, many receptors are needed to produce the collisional limit, and spare receptors may represent nature's evolution toward a reaction that provides the maximum rate as well as the maximum sensitivity to a ligand. Since receptors or enzymes provided on small membrane fragments will not function at the collisional limit, properties of reconstituted enzymes or receptors may not be extrapolated to the physiological situation. The use of normal bimolecular kinetic or equilibrium equations is inappropriate for reactions limited by collision and can give unusual results that lead to inappropriate conclusions. Determination of whether the collisional limit applies to a membrane-bound system is important for understanding its properties and those of the physiological circumstance.
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U2 - 10.1096/fasebj.2.13.2844615
DO - 10.1096/fasebj.2.13.2844615
M3 - Review article
C2 - 2844615
AN - SCOPUS:0023811158
SN - 0892-6638
VL - 2
SP - 2858
EP - 2866
JO - FASEB Journal
JF - FASEB Journal
IS - 13
ER -