Defense against chitin-containing fungal pathogens. Has in vitro antifungal activity against F.oxysporum inhibiting its growth and the branching of its hyphae. Has endochitinase activity, but no exochitinase or lysozyme activities. Random endo-hydrolysis of N-acetyl-beta-D-glucosaminide (1->4)-beta-linkages in chitin and chitodextrins. Expressed in the pulp of the fruit (at protein level) (PubMed:9679856, PubMed:14610495, PubMed:23019098). Expressed in mesocarp (at protein level) (PubMed:9774427). Causes an allergic reaction in human (PubMed:9774427, PubMed:9679856, PubMed:10231327, PubMed:14610495, PubMed:10482846, PubMed:10887324, PubMed:16433216, PubMed:18205857, PubMed:21284746). Involved (at least via the N-terminal chitin-binding hevein-like domain) in cross-reactions with natural rubber latex (latex-fruit allergy syndrome) (PubMed:9774427, PubMed:9679856, PubMed:10231327, PubMed:14610495, PubMed:10482846, PubMed:10887324, PubMed:16433216). Binds to IgE of patients allergic to avocado, chestnut and/or banana (PubMed:9679856, PubMed:10482846, PubMed:16433216, PubMed:21284746). Binds to IgE in 75% of the 20 patients tested allergic to latex (PubMed:9774427). Binds to IgE in 80% of the 15 patients tested allergic to avocado and latex (PubMed:10231327). Binds to IgE in 53% of the 92 and 38% of the 26 kiwifruit-allergic patients tested by ELISA and IgE immunodetection assays, respectively. Only 12% of the 25 kiwifruit-allergic patients tested are found positive by skin prick test (PubMed:18205857). Binds to IgE in 29% of the 51 pediatric patients tested allergic to banana (PubMed:21284746). IgE-binding is not abolished by digestion with artificial gastric juice or simulated gastric fluid (PubMed:10231327, PubMed:14610495). In vitro IgE-binding and in vivo allergenicity (skin prick test) is abolished by heating (PubMed:10887324). Induces degranulation of human basohphils and histamine release (PubMed:16433216). Belongs to the glycosyl hydrolase 19 family. Chitinase class I subfamily.