CYP2C40, a unique arachidonic acid 16-hydroxylase, is the major CYP2C in murine intestinal tract

We recently identified five different murine CYP2C cDNAs from a murine cDNA library. When expressed in a bacterial cDNA expression system, all five re combinant proteins metabolized arachidonic acid but produced distinctly dif ferent profiles. In addition, some CYP2C mRNAs were found in extrahepatic t issues, as well as in liver. Immunoblots with an antibody raised against re combinant CYP2C38, which recognizes all five murine CYP2Cs, demonstrated th at among extrahepatic tissues, colon and cecum contained the highest amount of CYP2Cs. The highest concentration of CYP2Cs occurred in cecum and colon (cecum greater than or equal to proximal colon much greater than distal co lon), with lower levels in duodenum, jejunum, and ileum. Immunohistochemica l studies revealed that CYP2Cs were localized principally in epithelial cel ls and autonomic ganglia in gut and colon. Polymerase chain reaction amplif ication of reverse-transcribed mRNA using murine CYP2C-specific primers fol lowed by cloning and sequencing identified CYP2C40 as the major CYP2C isofo rm expressed in murine intestinal tract. Recombinant CYP2C40 metabolized ar achidonic acid in a regio- and stereospecific manner to 16(R)-HETE (hydroxy eicosatetraenoic acid) as the major product. To our knowledge, CYP2C40 is t he first enzyme known to produce primarily 16-HETE. We conclude that CYP2C4 0 is one of the major cytochrome P450 proteins in the mouse intestinal trac t. In the light of vasoactive and anti-neutrophilic effects of 16-HETE, we hypothesize that CYP2C40 may play an important role in endogenous biologica l functions in intestine.