Activation of the PKC‐isotypes α, β1, γ, δ, and ε by phorbol esters of different biological activities

Abstract
Phorbol esters, tetradecanoylphorbolacetate, sapintoxin-A, 12-deoxyphorbol-phenylacetate, 12-deoxyphorbol-phenylacetate-20-acetate, thymeleatoxin and resiniferatoxin were investigated for their abilities to activate the PKC-isotypes α, β1, γ, δ and ε. PKC-isotypes were grouped into two classes on the basis of Ca2+ requirements for activation by phorbol esters; α, β1, and γ being Ca2+-dependent forms and δ and ε being Ca2+-independent. PKC-isotype selective activation by phorbol esters was observed in that SAPA failed to activate PKC-δ up to a concentration of 1000 ng ml−1 and DOPPA only activated PKC-β1, over the same range of concentrations.