In vitro studies of the inhibition of protein kinase C from rat brain by di-(2-ethylhexyl)phthalate.
The environmental contaminant di(2-ethylhexyl)phthalate (DEHP) has been shown to inhibit the phosphorylation of histone by purified protein kinase C (PK-C) from rat brain in a concentration-dependent manner. The inhibition does not involve making the substrate unavailable, although DEHP does bind to some extent to histone. DEHP displaces phorbol dibutyrate from PK-C, indicating that DEHP binds to the regulatory domain of the enzyme. Since DEHP does not affect the PK-C dependent phosphorylation of protamine, DEHP probably does not bind at the catalytic site. DEHP non-competitively blocked activation of PK-C by either phosphatidyl serine or calcium ion. Inhibition of histone phosphorylation by DEHP was enhanced if diglyceride was present, and the enhancement was stereoselective for the isomeric form of the diglyceride. The mechanism of the inhibition is thought to involve interference with the interaction between calcium ion and the regulatory domain of PK-C, and would have significance only for those PK-C substrates that require calcium activation of the enzyme. Thus the presence of DEHP in the high nanomolar concentration range alters the effective substrate specificity of PK-C.
Shukla
R R
RR
Laboratory of Molecular Biophysics, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709.
Albro
P W
PW
Corbett
J T
JT
Schroeder
J L
JL
D000818:Animals; D001921:Brain / Q000201:enzymology; D002118:Calcium / Q000494:pharmacology; D004051:Diethylhexyl Phthalate / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010718:Phosphatidylserines / Q000494:pharmacology; D010795:Phthalic Acids / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D051381:Rats; D013379:Substrate Specificity
D010718:Phosphatidylserines; D010795:Phthalic Acids; D015240:Phorbol 12,13-Dibutyrate; D004051:Diethylhexyl Phthalate; D011493:Protein Kinase C; D002118:Calcium