JBC, Vol. 250, Issue 12, 4423-4426, Jun, 1975
Role of the surface excess of palmitoyl coenzyme A in the 1-acylglycerol-3-phosphate acyltransferase reaction catalyzed by microsomes
H. L. Brockman
Surface excess values for palmitoyl-coenzyme A have been determined at the
air-water interface. In the bulk concentration range of 0.23 to 3.7 muM,
the surface concentration of palmitoyl-CoA ranges from 0.7 to 1.4 times 10-
minus 10 mol/cm-2. The molecules of palmitoyl-CoA in the surface layer
behave as if they were in a monolayer with each molecule occupying a
limiting molecular area of 79 A-2. The distribution of palmitoyl-CoA
between bulk and surface phases can be described by a Langmuir adsorption
isotherm with an equilibrium constant of 0.33 muM. This constant is
identical to the apparent Km for palmitoyl-CoA in the
1-acylglycerol-3-phosphate acyltransferase reaction catalyzed by
microsomes. The results of this study, together with those from earlier
work, suggest that the observed saturation behavior of the enzymatic
reaction reflects the formation of a positive surface excess of
palmitoyl-CoA in the vicinity of the catalytic site.