Angiotensin-converting enzyme (ACE) is a carboxyl-terminal dipeptidyl exopeptidase
that converts Angiotensin I to the potent vasopressive hormone, Angiotensin
II. There are two isoforms of ACE, the pulmonary ACEP and the testicular
ACET. ACEP is a glycoprotein expressed in vascular endothelial cells of
the lung, liver, adrenal cortex, pancreas, kidney and spleen. The ACET isoform
is expressed exclusively in adult testis by developing sperm cells, specifically
late pachytene spermatocytes. Additionally, ACE inactivates bradykinin, a
vasodepressor peptide, and is involved in blood pressure regulation and fluid/
electrolyte homeostasis. ACE2 is the first known human homolog of angiotensin-
converting enzyme (ACE). Unlike ACE, which is expressed ubiquitously
throughout the vasculature, ACE2 is expressed only in cardiac, renal and
testicular cells.