The functional importance of the N-terminal region of human prolylcarboxypeptidase

Abstract

The renin–angiotensin-system cascade pathway generates the vasopressor and prothrombotic hormones, angiotensin II (Ang II) and angiotensin III (Ang III) from angiotensinogen. One of the key enzymes for the generation of angiotensin 1–7 (Ang 1–7) and angiotensin 2–7 (Ang 2–7) from Ang II and III, respectively, is prolylcarboxypeptidase (PRCP). To understand the contribution of the N-terminal region to catalysis, an N-terminal truncated form, lacking 179 N-terminal residues of PRCP (rPRCP 40) was constructed. The circular dichroism (CD) spectrum of rPRCP 40 illustrated that it was structured with significant helical content as indicated by local minima at ∼220 and 208 nm. The main products of Ang III metabolized by rPRCP 40 were Ang 2–7 plus phenylalanine as determined by LC–MS. Angiotensin I (Ang I) blocked the metabolism of Ang III by rPRCP 40. These investigations showed that the C-terminal region of the rPRCP 40 contributes to PRCP’s catalytic function, and provided additional experimental evidence for this suggestion.