Phenobarbital competes with diacylglycerol for protein kinase C.

Phenobarbital inhibits protein kinase C of rat brain by competitively displacing the effector of the enzyme, diacylglycerol. The drug appears to occupy the triple hydrogen bonding site which bonds diacylglycerol - and also phorbol esters - to the enzyme. It remains to be seen if the effect is responsible for the pharmaceutical activity of the drug; even so, it provides an example of a restructuring of lipid-protein hydrogen bonding, in the hydrogen belt of the membrane, in a manner postulated as a mechanism of anesthesia.