A Novel Member, PC7, of the Mammalian Kexin-like Protease Family - Homology to PACE4A, Its Brain-Specific Expression and Identification of Isoforms

By polymerase chain reaction (PCR) with primers corresponding to the sequences of catalytic domain conserved among the mammalian kexin-like protease family, a cDNA fragment encoding a novel member of the family was obtained from rat pituitary. A cDNA for the novel protease was obtained from three overlapping clones isolated from a rat pituitary cDNA library using the PCR product as a screening probe. The protein, designated as PC7, encoded by this cDNA contained a putative activation site with the sequence RXKR, subtilisin-like catalytic domain and a home B region which are typical of mammalian kexin-like proteases, and short cysteine-rich region at the carboxyl-terminal end. It exhibited surprising sequence similarity to PACE4A. The PC7 transcript was expressed at high levels in the brain. However it was undetectable in the liver, kidney, heart, and spleen. The presence of PC7 isoforms (PC7A and PC7B) was also shown.