May act as a protease inhibitor. Expressed by the venom gland. in Api m 6.01. in Api m 6.02. in Api m 6.03. in Api m 6.04. Causes an allergic reaction in human (PubMed:11344362, PubMed:23397669). Binds to IgE (42% responsiveness) (PubMed:11344362, PubMed:23397669). Belongs to the serine protease inhibitor-like (TIL domain-containing) family. Four isoforms exist; 6.01 (without 4 N-ter AA and 2 extra C-ter AA), 6.02 (without 4 N-ter AA but with 2 extra C-ter AA), 6.03 (with 4 N-ter AA but without 2 extra C-ter AA) and 6.04 (with 4 N-ter AA and with 2 extra C-ter AA) (PubMed:17069633, PubMed:11344362). The sequence displayed corresponds to isoform 6.03. It is unknown if the variants api m 6.01 and api m 6.02 (without 4 N-ter AA) are the result of different transcript, an alternative splicing, or an enzymatic cleavage.