K-252a, also known as SF 2370, is an alkaloid isolated from Nocardiopisis bacteria. This staurosporine analog is a highly potent cell permeable inhibitor of CaM kinase and phosphorylase kinase (IC50 = 1.8 and 1.7 nmol/L, respectively). At higher concentrations it is also an efficient inhibitor of serine/threonine protein kinases (IC50 of 10 to 30 nmol/L).

[1] Fujikawa-Yamamoto K, Miyagoshi M, Yamagishi H. Polyploidization of 2nH1 (ES) cells by K-252a and staurosporine. Hum Cell. 2007 Nov;20(4):91-9. PubMed PMID: 17949348.

[2] Schiering N, Knapp S, Marconi M, Flocco MM, Cui J, Perego R, Rusconi L, Cristiani C. Crystal structure of the tyrosine kinase domain of the hepatocyte growth factor receptor c-Met and its complex with the microbial alkaloid K-252a. Proc Natl Acad Sci U S A. 2003 Oct 28;100(22):12654-9. Epub 2003 Oct 14. PubMed PMID: 14559966; PubMed Central PMCID: PMC240673.

[3] Kino M, Shono K, Nishimura T, Nagamura S. Practical Preparation of K-252a from a Fermentation Solution. Biosci Biotechnol Biochem. 1998;62(8):1627-9. doi: 10.1271/bbb.62.1627. PubMed PMID: 27388849.

[4] Hudkins RL, Johnson NW, Angeles TS, Gessner GW, Mallamo JP. Synthesis and mixed lineage kinase activity of pyrrolocarbazole and isoindolone analogs of (+)K-252a. J Med Chem. 2007 Feb 8;50(3):433-41. PubMed PMID: 17266195.