C9ORF3 Messenger RNA has been detected in human pancreas, placenta, liver, testis, and heart. The expression in the heart suggests this enzyme may also play a role in the regulating the physiology of cardiac muscle. Several ApO isoforms are expressed predominantly in blood vessels suggesting that ApO plays a role in vascular cell biology.
^ abcdDíaz-Perales A, Quesada V, Sánchez LM, Ugalde AP, Suárez MF, Fueyo A, López-Otín C (April 2005). "Identification of human aminopeptidase O, a novel metalloprotease with structural similarity to aminopeptidase B and leukotriene A4 hydrolase". J. Biol. Chem. 280 (14): 14310–7. PMID15687497. doi:10.1074/jbc.M413222200.
^ abAxton R, Wallis JA, Taylor H, Hanks M, Forrester LM (March 2008). "Aminopeptidase O contains a functional nucleolar localization signal and is implicated in vascular biology". J. Cell. Biochem. 103 (4): 1171–82. PMID17803194. doi:10.1002/jcb.21497.