Different contributions of the angiotensin-converting enzyme C-domain and N-domain in subjects with the angiotensin-converting enzyme II and DD genotype.
BACKGROUND
Angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism-related differences in ACE concentration do not result in differences in angiotensin levels.


RESULTS
To investigate whether this relates to differences in the contribution of the ACE C-domain and N-domain, we quantified, using the C-domain-selective inhibitors quinaprilat and RXPA380, and the N-domain-selective inhibitor RXP407, the contribution of both domains to the metabolism of angiotensin I, bradykinin, the C-domain-selective substrate Mca-BK(1-8), and the N-domain-selective substrate Mca-Ala in serum of IIs, DDs, and 'hyperACE' subjects (i.e., subjects with increased ACE due to enhanced shedding). During incubation with angiotensin I, the highest angiotensin II levels were observed in sera with the highest ACE activity. This confirms that ACE is rate-limiting with regard to angiotensin II generation. C-domain-selective concentrations of quinaprilat fully blocked angiotensin I-II conversion in DDs, whereas additional N-domain blockade was required to fully block conversion in IIs. Both domains contributed to bradykinin hydrolysis in all subjects, and the inhibition profile of RXP407 when using Mca-Ala was identical in IIs and DDs. In contrast, the RXPA380 concentrations required to block C-domain activity when using Mca-BK (1-8) were three-fold higher in IIs than DDs.


CONCLUSIONS
The contributions of the C-domain and N-domain differ between DDs and IIs, and RXPA380 is the first inhibitor capable of distinguishing D-allele ACE from I-allele ACE. The lack of angiotensin II accumulation in DDs in vivo is not because of the often quoted concept that ACE is a nonrate-limiting enzyme. It may relate to the fact that in IIs both the N-domain and C- domain generate angiotensin II, whereas in DDs only the C-domain converts angiotensin I.
van Esch
Joep H M
JH
Division of Vascular Pharmacology and Metabolism, Erasmus MC, Rotterdam, The Netherlands.
van Gool
Jeanette M G
JM
de Bruin
René J A
RJ
Payne
John R
JR
Montgomery
Hugh E
HE
Hectors
Magda
M
Deinum
Jaap
J
Dive
Vincent
V
Jan Danser
A H
AH
D000328:Adult; D000368:Aged; D000803:Angiotensin I / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology*; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D005838:Genotype; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D009842:Oligopeptides / Q000494:pharmacology*; D007703:Peptidyl-Dipeptidase A / Q000097:blood* / Q000737:chemistry / Q000235:genetics*; D010721:Phosphinic Acids / Q000494:pharmacology*; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D034421:Sus scrofa; D044005:Tetrahydroisoquinolines / Q000494:pharmacology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
D000806:Angiotensin-Converting Enzyme Inhibitors; D009842:Oligopeptides; D010721:Phosphinic Acids; C118733:RXP 407; C476531:RXPA380; D044005:Tetrahydroisoquinolines; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D000804:Angiotensin II; C010980:hippuryl-histidyl-leucine; C054501:quinaprilat; D000803:Angiotensin I; D007703:Peptidyl-Dipeptidase A; D001920:Bradykinin