J. Biol. Chem., Vol. 261, Issue 17, 7816-7818, Jun, 1986
The tumor promoter 12-O-tetradecanoyl phorbol 13-acetate and regulatory diacylglycerols are substrates for the same carboxylesterase
R Mentlein
Rat liver homogenate or cell fractions deacylate 12-O-tetradecanoyl phorbol
13-acetate (TPA) in vitro mainly by conversion to phorbol 13- acetate. The
highest specific activity is located in the microsomal fraction. The
deacylation is inhibited by bis-(4-nitrophenyl) phosphate, a selective
inhibitor of nonspecific carboxylesterases. Only two of five purified
esterases from rat liver endoplasmic reticulum deacylate TPA. These two
esterases have formerly been characterized as acylcarnitine hydrolases and
the more active one is also a potent diacylglycerol lipase. Its
TPA-hydrolyzing activity is inhibited by other substrates like
1-naphthylacetate, lauroylcarnitine, or dioleoyl glycerol. The results
support the view that phorbol esters act like structural analogs of
diacylglycerols, not only with respect to their activating effect on
protein kinase C, but also as substrates for the same lipases.