Calphostin C (UCN-1028C), a novel microbial compound, is a highly potent and specific inhibitor of protein kinase C

Biochem Biophys Res Commun. 1989 Mar 15;159(2):548-53. doi: 10.1016/0006-291x(89)90028-4.


Calphostin C (UCN-1028C), a newly isolated compound from Cladosporium cladosporioides, is a potent and specific inhibitor of protein kinase C, because it was 1000 times more inhibitory to protein kinase C (IC50, 0.05 microM) than other protein kinases such as cAMP-dependent protein kinase and tyrosine-specific protein kinase (IC50, greater than 50 microM). Calphostin C did not inhibit calcium activated neutral protease (calpain)-digested protein kinase C, indicating that it interacts with the regulatory domain of protein kinase C. In addition this compound showed inhibitory effects on the binding of [3H]PDBu to protein kinase C. The potent cytotoxic activity and antitumor activity of calphostin C might be due to the inhibition of protein kinase C, and thus it may be potentially useful for the therapeutic application.

MeSH terms

  • Animals
  • Antineoplastic Agents / pharmacology
  • Caenorhabditis elegans Proteins*
  • Carrier Proteins
  • Cell Division / drug effects
  • Cladosporium / analysis*
  • Fungal Proteins / pharmacology*
  • HeLa Cells / metabolism
  • Humans
  • Mitosporic Fungi / analysis*
  • Naphthalenes*
  • Phorbol Esters / metabolism
  • Polycyclic Compounds / pharmacology*
  • Protein Kinase C / antagonists & inhibitors*
  • Rats
  • Receptors, Drug / drug effects


  • Antineoplastic Agents
  • Caenorhabditis elegans Proteins
  • Carrier Proteins
  • Fungal Proteins
  • Naphthalenes
  • Phorbol Esters
  • Polycyclic Compounds
  • Receptors, Drug
  • phorbol ester binding protein
  • phorbol ester receptor
  • Protein Kinase C
  • calphostin C