Indolocarbazoles are compounds with a 6-ring-fused plane structure, which mimics ATP. Therefore, compounds containing an indolocarbazole core could be used to inhibit protein kinases such as Protein Kinase A (PKA) and Protein Kinase C (PKC), and are potential candidates of antitumor drugs. Staurosporine, an indolocarbazole compound, is biosynthesized by Streptomyces sp. TP-A0274. A whole set of biosynthetic genes have been already cloned, and these studies revealed that 4 enzymes, StaO, StaD, StaP, and StaC, are responsible for indolocarbazole core biosynthesis. The starter unit for the indolocarbazole core is 2 molecules of tryptophane. In the biosynthesis, StaO that encodes a monooxygenase, catalyzes the conversion from tryptophane to the indolepyruvic acid imine form (IPA imine). StaD then catalyzes the intermolecular-coupling reaction of 2 IPA imines to give a chromopyrrolic acid (CPA), which is a key intermediate of indolocarbazoles. Finally, intramolecular C-C bonds are formed between indole rings, followed by oxidation of the pyrrole moiety by StaP and StaC to yield K252c, an indolocarbazole core.