The function of Ensembl gene identifier ENSG00000159640 (ACE, angiotensin I converting enzyme) is as follows. Dipeptidyl carboxypeptidase that removes dipeptides from the C-terminus of a variety of circulating hormones, such as angiotensin I, bradykinin or enkephalins, thereby playing a key role in the regulation of blood pressure, electrolyte homeostasis or synaptic plasticity (PubMed:15615692, PubMed:20826823, PubMed:2558109, PubMed:4322742, PubMed:7523412, PubMed:7683654). Composed of two similar catalytic domains, each possessing a functional active site, with different selectivity for substrates (PubMed:10913258, PubMed:1320019, PubMed:1851160, PubMed:19773553, PubMed:7683654, PubMed:7876104). Plays a major role in the angiotensin-renin system that regulates blood pressure and sodium retention by the kidney by converting angiotensin I to angiotensin II, resulting in an increase of the vasoconstrictor activity of angiotensin (PubMed:11432860, PubMed:1851160, PubMed:19773553, PubMed:23056909, PubMed:4322742). Also able to inactivate bradykinin, a potent vasodilator, and therefore enhance the blood pressure response (PubMed:15615692, PubMed:2558109, PubMed:4322742, PubMed:6055465, PubMed:6270633, PubMed:7683654). Acts as a regulator of synaptic transmission by mediating cleavage of neuropeptide hormones, such as substance P, neurotensin or enkephalins (PubMed:15615692, PubMed:6208535, PubMed:6270633, PubMed:656131). Catalyzes degradation of different enkephalin neuropeptides (Met- enkephalin, Leu-enkephalin, Met-enkephalin-Arg-Phe and possibly Met- enkephalin-Arg-Gly-Leu) (PubMed:2982830, PubMed:6270633, PubMed:656131). Acts as a regulator of synaptic plasticity in the nucleus accumbens of the brain by mediating cleavage of Met-enkephalin- Arg-Phe, a strong ligand of Mu-type opioid receptor OPRM1, into Met- enkephalin (By similarity). Met-enkephalin-Arg-Phe cleavage by ACE decreases activation of OPRM1, leading to long-term synaptic potentiation of glutamate release (By similarity). Also acts as a regulator of hematopoietic stem cell differentiation by mediating degradation of hemoregulatory peptide N-acetyl-SDKP (AcSDKP) (PubMed:26403559, PubMed:7876104, PubMed:8257427, PubMed:8609242). Acts as a regulator of cannabinoid signaling pathway by mediating degradation of hemopressin, an antagonist peptide of the cannabinoid receptor CNR1 (PubMed:18077343). Involved in amyloid-beta metabolism by catalyzing degradation of Amyloid-beta protein 40 and Amyloid-beta protein 42 peptides, thereby preventing plaque formation (PubMed:11604391, PubMed:16154999, PubMed:19773553). Catalyzes cleavage of cholecystokinin (maturation of Cholecystokinin-8 and Cholecystokinin-5) and Gonadoliberin-1 (both maturation and degradation) hormones (PubMed:10336644, PubMed:2983326, PubMed:7683654, PubMed:9371719). Degradation of hemoregulatory peptide N-acetyl-SDKP (AcSDKP) and amyloid-beta proteins is mediated by the N-terminal catalytic domain, while angiotensin I and cholecystokinin cleavage is mediated by the C-terminal catalytic region (PubMed:10336644, PubMed:19773553, PubMed:7876104). {ECO:0000250|UniProtKB:P09470, ECO:0000269|PubMed:10336644, ECO:0000269|PubMed:10913258, ECO:0000269|PubMed:11432860, ECO:0000269|PubMed:11604391, ECO:0000269|PubMed:1320019, ECO:0000269|PubMed:15615692, ECO:0000269|PubMed:16154999, ECO:0000269|PubMed:18077343, ECO:0000269|PubMed:1851160, ECO:0000269|PubMed:19773553, ECO:0000269|PubMed:20826823, ECO:0000269|PubMed:23056909, ECO:0000269|PubMed:2558109, ECO:0000269|PubMed:26403559, ECO:0000269|PubMed:2982830, ECO:0000269|PubMed:2983326, ECO:0000269|PubMed:4322742, ECO:0000269|PubMed:6055465, ECO:0000269|PubMed:6208535, ECO:0000269|PubMed:6270633, ECO:0000269|PubMed:656131, ECO:0000269|PubMed:7523412, ECO:0000269|PubMed:7683654, ECO:0000269|PubMed:7876104, ECO:0000269|PubMed:8257427, ECO:0000269|PubMed:8609242, ECO:0000269|PubMed:9371719}. [Angiotensin-converting enzyme, soluble form]: Soluble form that is released in blood plasma and other body fluids following proteolytic cleavage in the juxtamembrane stalk region. {ECO:0000269|PubMed:10769174, ECO:0000269|PubMed:11274151, ECO:0000269|PubMed:7499427, ECO:0000269|PubMed:8253769}. [Isoform Testis-specific]: Isoform produced by alternative promoter usage that is specifically expressed in spermatocytes and adult testis, and which is required for male fertility (PubMed:1651327, PubMed:1668266). In contrast to somatic isoforms, only contains one catalytic domain (PubMed:1651327, PubMed:1668266). Acts as a dipeptidyl carboxypeptidase that removes dipeptides from the C-terminus of substrates (PubMed:1668266, PubMed:24297181). The identity of substrates that are needed for male fertility is unknown (By similarity). May also have a glycosidase activity which releases GPI- anchored proteins from the membrane by cleaving the mannose linkage in the GPI moiety. The GPIase activity was reported to be essential for the egg-binding ability of the sperm (By similarity). This activity is however unclear and has been challenged by other groups, suggesting that it may be indirect (By similarity). {ECO:0000250|UniProtKB:P09470, ECO:0000269|PubMed:1651327, ECO:0000269|PubMed:1668266, ECO:0000269|PubMed:24297181}.