Tryptase alpha/beta 1 (TPSAB1) is one of two adjacent genes (TPSAB1, TPSB2) that code for mast cell tryptase, a serine protease. Mast cell tryptase is the predominant isoenzyme in mast cells. It is often used as a marker for mast cell activation, and high levels of tryptase can be an indicator of anaphylaxis, mastocytosis or the presence of eosinophilic leukemia. In immunohistochemistry, antibodies to mast cell tryptase stain secretory granules of mast cells. References: J Biol Chem. 1999. 274 (6): 3355–62,PMID: 9920877; Nat Genet. 2016 Dec;48(12):1564-1569, PMID: 27749843; Proceedings of the National Academy of Sciences of the United States of America. 1990 May. 87 (10): 3811–5, PMID: 2187193; Cancer Research. 2017 Mar. 77 (6): 1261–1270, PMID: 28254862; Am. J. Clin. Path. 2015 Sept. 144 (3): 377–92, PMID 26276769; Anaesthesia. 2004 Jul;59(7):695-703, PMID: 15200544