Staurosporine‐related compounds, K252a and UCN‐01, inhibit both cPKC and nPKC

The potent inhibitors of protein kinase C (PKC), H7, staurosporine, and staurosporine derivatives, were examined for their inhibitory effects on novel PKC (nPKC) isozymes delta and epsilon. H7 and staurosporine, usually used as selective inhibitors of PKC, showed similar inhibitory effects on cPKC (a mixture of cPKC alpha, beta, and gamma) and nPKC delta and epsilon. The inhibitory effects of K252a, a non-selective protein kinase inhibitor, on cPKC was 3.2- and 22-fold higher than those on nPKC epsilon and delta, respectively. The staurosporine derivatives UCN-01 and UCN-01-Me also showed selective inhibition of cPKC.