title: Serum lipase active in the hydrolysis of the tumor promoter, 12-O-tetradecanoylphorbol-13-acetate.
abstract: Sera from numerous animal sources contain enzymes that degrade the potent tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA). The activity was present in rat, mouse, guinea pig, rabbit and goat, and absent in fetal bovine, bovine, porcine, horse, chicken and human sera. The enzyme shows a marked specificity for hydrolysis of the long-chain 12-O acyl group, which results in the formation of phorbol-13-monoacetate as the major product. Enzymatic catalysis displayed two pH optima (5.5 and 8.0) and was completely destroyed by heat inactivation (56 degrees C, 30 min) of the serum. N-Ethylmaleimide and p-chloromercuribenzoate were relatively weak inhibitors, whereas NaF (5.0 mM) produced an approximate 80% reduction of hydrolysis. Esterase-lipase substrates, such as cholesterol oleate, alpha-naphthylacetate, alpha-naphthylpalmitate, and monotetradecanoylglycerol, were not inhibitory when added to the reaction mixture. Porcine pancreatic lipase does not catalyze the removal of the acyl or the acetyl groups from TPA.
mesh_terms: D000818:Animals; D004355:Drug Stability; D006041:Goats; D006168:Guinea Pigs; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D008049:Lipase / Q000097:blood*; D008297:Male; D051379:Mice; D010704:Phorbols / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D013045:Species Specificity; D013755:Tetradecanoylphorbol Acetate / Q000378:metabolism*
chemical_list: D010704:Phorbols; D008049:Lipase; D013755:Tetradecanoylphorbol Acetate