CLONING OF THE PABA PEPTIDE-HYDROLASE ALPHA-SUBUNIT (PPH-ALPHA) FROM HUMAN SMALL-INTESTINE AND ITS EXPRESSION IN COS-1 CELLS

PABA peptide hydrolase (PPH) from human enterocytes is comprised of two subunits, alpha and beta. PPH alpha is over 70% identical to meprin, a protease isolated from mouse and rat kidney. The enzyme shows a modular organization in that it contains an astacin protease domain, an adhesive domain, an EGF-like domain, and a putative C-terminal membrane spanning domain. Expression of a chimeric meprin-PPH alpha cDNA in COS-1 cells led to the synthesis of immature, transport-incompetent homodimers. In addition, complex glycosylated forms were detected in the culture medium, suggesting that the enzyme is secreted after proteolytic removal of the membrane anchor.