| First Author | Ahmad S | Year | 2019 |
| Journal | Biochem Biophys Res Commun | Volume | 518 |
| Issue | 4 | Pages | 651-656 |
| PubMed ID | 31466718 | Mgi Jnum | J:359378 |
| Mgi Id | MGI:7787312 | Doi | 10.1016/j.bbrc.2019.08.098 |
| Citation | Ahmad S, et al. (2019) Mast cell peptidases (carboxypeptidase A and chymase)-mediated hydrolysis of human angiotensin-(1-12) substrate. Biochem Biophys Res Commun 518(4):651-656 |
| abstractText | Angiotensin processing peptidases (carboxypeptidase A (CPA) and chymase) are stored in cardiac mast cell (MC) secretory granules in large quantity and are co-released into the extracellular environment after activation/degranulation. In the human heart, chymase is primarily responsible for angiotensin II (Ang II) generation from the alternate substrate angiotensin-(1-12) (Ang-(1-12)). We investigated the individual and combined hydrolytic specificity of CPA and chymase enzymes (1:1 and 1:(1/3) ratio) in the processing of the human Ang-(1-12) (hAng-(1-12)) substrate. To determine the K(m) and V(max), the CPA and recombinant human chymase (rhChymase) enzymes were incubated with increasing concentrations of hAng-(1-12) substrate (0-300muM). We found that CPA alone sequentially metabolized hAng-(1-12) substrate into angiotensin-(1-9) (Ang-(1-9), 53%), Ang II (22%) and angiotensin-(1-7) (Ang-(1-7), 11%) during a 15min incubation. In the presence of rhChymase alone, (125)I-hAng-(1-12) was directly metabolized into Ang II (89%) and no further hydrolysis of Ang II was detected. In the presence of both CPA + rhChymase enzymes (1:1 or 1:(1/3) ratio), the amount of Ang II formation from (125)I-hAng-(1-12) within a 5 min incubation period were 68% or 65%, respectively. In the presence of both (CPA + rhChymase), small amounts of Ang-(1-9) and Ang-(1-7) were generated from (125)I-hAng-(1-12). The K(m) and V(max) values were 150+/-5muM and 384+/-23nM/min/mg of CPA and 40+/-9muM and 116+/-20nM/min/mg of rhChymase. The catalytic efficiency (V(max)/K(m) ratio) was higher for rhChymase/hAng-(1-12) compared to CPA/hAng-(1-12). Compared to CPA, chymase has a much higher affinity to hydrolyze the hAng-(1-12) substrate directly into Ang II. In addition, Ang II and Ang-(1-7) are the end products of chymase and CPA, respectively. Overall, our findings suggest that the Ang II generation from hAng-(1-12) is primarily mediated by chymase rather than CPA. |
