Genotypic influence on plasma dipeptidyl carboxypeptidase-1 activity in hypertensives

1. Plasma dipeptidyl carboxypeptidase-1 (DCP1; angiotensin I-converting enzyme, kininase II; EC 3.4.15.1) tracks with the deletion allele in genotypes of a 287 bp insertion/deletion (I/D) polymorphism of its gene, DCP1, in healthy Caucasian populations. The aim of the present study was to see whether genotype has a similar influence on plasma DCP1 in hypertensives. 2. The study involved 35 Caucasian patients with severe, familial essential hypertension, who were not being treated with DCP1 inhibitors, and 94 normotensives. Genotyping for the I/D polymorphism was performed by polymerase chain reaction and plasma DCP1 activity was measured by rate of hydrolysis of both [3H]-Hip-Gly-Gly and Hip-His-Leu. 3. Plasma DCP1 activity (nmol Gly-Gly/min per mL; mean +/- s.e.m.) was 67 +/- 2, 82 +/- 4 and 91 +/- 6 in II, ID and DD hypertensives, respectively, which was similar to values of 68 +/- 4, 82 +/- 3 and 94 +/- 3 in normotensives (P = 0.0001 by one-way analysis of variance). Results for the His-Leu assay indicated similar tracking with genotype. 4. The Michaelis constant (mumol Hip-Gly-Gly/mL; mean +/- s.e.m., n = 10) for DD subjects was the same as for II subjects (10.6 +/- 1.6 vs 11.1 +/- 2.3; P = 0.86). 5. In conclusion, in severely hypertensive Caucasian subjects, plasma DCP1 activity is subject to a similar genotypic influence in hypertensives as has been reported previously in normotensives. Furthermore, the plasma DCP1 enzyme itself appears to be functionally similar for each genotype.