Identification of an isoform with an extremely large Cys-rich region of PC6, a Kex2-like processing endoprotease.

In the previous study [1993, J. Biochem. (Tokyo) 113, 132-135] we identified PC6, a member of the Kex2 family of processing endoproteases. In this study, we identified another cDNA encoding an isoform of PC6, and designated it as PC6B and redesignated the originally identified PC6 as PC6A. PC6B had a very large Cys-rich region consisting of 22-times repeats of a Cys-rich motif, and a putative transmembrane domain which is not present in PC6A. A PC6B transcript was found mainly in the intestine, while PC6A transcripts were in various tissues. These results suggest distinct roles of PC6A and PC6B in endoproteolytic processing of precursor proteins.