ACE (Angiotensin-converting enzyme, CD143) is an enzyme involved in catalyzing the conversion of angiotensin I into the physiologically active angiotensin II. It has a central role in the renin-angiotensin system, which is involved in regulating blood pressure and fluid volume in the body. The 287 bp Alu repeat element in this gene is correlated with levels of circulating ACE enzyme and with cardiovascular patho-physiologies. Variants in ACE are also associated with Alzheimer’s disease, where deregulated levels of the protein have been found. In immunohistochemistry, ACE has positive staining in the lung capillary endothelium, basal ganglia neuropil, granulosa cells, Leydig cells, proximal renal tubule brush borders, the uterus, male genitalia, and endothelial cells of small or medium arteries. References: Am J Transl Res. 2011 Jan 1; 3(1): 73–80, PMID: 21139807; Alzheimers Res Ther. 2014; 6(3): 27, PMID: 24987467