Peptidyl-dipeptidase A/angiotensin I-converting enzyme

This chapter discusses the tissue distribution and the substrate specificity of peptidyl-dipeptidase A/angiotensin I-converting enzyme. Angiotensin I-Converting Enzyme (ACE) is a zinc metallopeptidase that belongs to the gluzincin family (clan MA) of metalloproteases of which thermolysin is the prototype. ACE cleaves the C-terminal dipeptide from angiotensin I to produce the potent vasopressor octapeptide angiotensin II and inactivates bradykinin by the sequential removal of two C-terminal dipeptides. In addition to these two main physiological substrates, which are involved in blood pressure regulation and water and salt metabolism, ACE cleaves C-terminal dipeptides from various oligopeptides with a free C-terminus. ACE is also able to cleave a C-terminal dipeptide-amide. The maximum expression of ACE occurs during the acrosome phase in murine species. ACE is exclusively produced in haploid germ cells and belongs to the group of proteins whose expression during definite maturation steps of spermiogenesis appears to be correlated with the unique process of germ cell differentiation. The inactivation of the ACE gene by homologous recombination leads to homozygous male mice with markedly reduced blood pressure, severe renal abnormalities and severely reduced fertility.