Inactivation of pancreatic and gastric lipases by THL and C12:0-TNB: a kinetic study with emulsified tributyrin.
THL is a potent inhibitor of pancreatic (PPL) and gastric (HGL, RGL) lipases. Inactivation occurs preferentially at the oil/water interface (method B, C). In the aqueous phase (method A), the inhibition of HGL was accelerated by the presence of bile salts. C12:0-TNB, a disulfide reagent, specifically inactivates gastric lipases and had no effect on the pancreatic lipase (in the presence of bile salts) whatever the method used. The capacity of THL and C12:0-TNB to inactivate lipases using Methods B and C was found to depend directly upon the interfacial area of the system used. Consequently, inactivation can be reduced or prevented by further addition of a water-insoluble substrate which reduces the surface density of inactivator molecules. With a heterogeneous system of this kind, typical of lipolysis, the use of a classical Michaelis-Menten model is irrelevant and hence the traditional kinetic parameters (Km, KI, Vmax) are only apparent values.
Gargouri
Y
Y
Centre de Biochimie et de Biologie Moléculaire du CNRS, Marseille, France.
Chahinian
H
H
Moreau
H
H
Ransac
S
S
Verger
R
R
D000818:Animals; D004655:Emulsions; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008049:Lipase / Q000037:antagonists & inhibitors* / Q000737:chemistry; D008066:Lipolysis / Q000187:drug effects; D010179:Pancreas / Q000201:enzymology*; D011817:Rabbits; D013270:Stomach / Q000201:enzymology*; D013552:Swine; D014280:Triglycerides / Q000494:pharmacology*
D004655:Emulsions; D014280:Triglycerides; D008049:Lipase; C005830:tributyrin