The stimulatory and inhibitory effects of glycyrrhizin and a glycyrrhetinic acid derivative on phosphorylation of lipocortin I by A-kinase in vitro.

The effects of GL and oGA on the activity (phosphorylation of lipocortin I) by A-kinase were investigated in vitro. It was found that (i) phosphorylation of the 35-36 kDa polypeptide by A-kinase was inhibited selectively when the partially purified kinase fraction from EAT cells was incubated with [gamma-32P]ATP in the presence of 60 microM oGA; (ii) the marked polypeptide was identified as a lipocortin I; and (iii) the activity of the kinase was stimulated about 4-fold by 5 microM oGA, but it was inhibited at doses above 25 microM. The drug-induced inhibition of phosphorylation of lipocortin I by A-kinase may be implicated in the anti-inflammatory effect of the drugs.