The elevation of diacylglycerol became of major importance when diacylglycerol was shown to stimulate protein kinase C, making this lipid candidate for a second messenger function in the signal transduction system. In intact cells, diacylglycerol is rapidly phosphorylated into phosphatidic acid by diacylglycerol kinase and reverses the protein kinase C activity.
DKI was found to inhibit diacylglycerol kinase. In human red blood cell membranes and in intact platelets, the concentrations needed for half maximal inhibition ranged from 2 to 4x10^-6M.