Saturday, February 27, 2010

Angiotensin I

Angiotensin I is an N-terminal decapeptide which is formed when renin acts on angiotensinogen. Angiotensin I is the precursor of angiotensin II. Renin is produced in the kidneys in response to both decreased intra-renal blood pressure at the juxtaglomerular cells, or decreased delivery of Na+ and Cl- to the macula densa. If more Na+ is sensed, renin release is decreased. Renin cleaves the peptide bond between the leucine (Leu) and valine (Val) residues on angiotensinogen, creating the ten amino acid peptide (des-Asp) angiotensin I (CAS# 9041-90-1). Angiotensin I appears to have no biological activity and exists solely as a precursor to angiotensin II.

Variants of the angiotensin I converting enzyme (peptidyl-dipeptidase A) 1 (ACE1) gene and the apolipoprotein E gene (APOE) have been suggested to be associated with human longevity. The association between the ACE1 insertion (I allele)/deletion (D allele) polymorphism and longevity have been tested in a population from Southern Italy and examined the impact of geographical variation on ACE1 allele frequencies on reported associations from other European countries. ACE1 and APOE genotypes were obtained on 82 centenarians and 252 middle-aged, unrelated subjects or volunteers. No statistically significant differences were found in ACE1 genotype or allele frequencies between centenarians and controls in this Southern Italian population nor was there any observed interaction with APOE alleles that are also reputed to be linked to longevity. However, decreasing gradients in ACE1*I allele frequencies, both in centenarians and controls, with concomitant increases in ACE1*D allele frequencies (particularly the ACE1*D/*D genotype) were observed to be statistically significant from Northern to Southern regions of Europe.