Part of an orally active toxin complex (TC) with strong insecticidal effects on larvae of the Coleoptera Costelytra zealandica, Acrossidius tasmania and Adoryphorus couloni and some Lepidoptera larvae (PubMed:21278295). The TC has an endochitinase activity (PubMed:21278295, PubMed:22158901) (Probable). This subunit might aid infection by degradation of the larval peritrophic membrane (Probable). Random endo-hydrolysis of N-acetyl-beta-D-glucosaminide (1->4)-beta-linkages in chitin and chitodextrins. Toxin complex is secreted when grown at 25 degrees Celsius or less; at higher temperatures the proteins are present intracellularly but not secreted. In the intact toxin complex the combined chitinase activity of Chi1 and Chi2 is slightly reduced. Optimum pH is 6.0, in the intact toxin complex optimum pH is pH 4.0 to pH 8.0. Semipurified toxin complex consists of at least YenA1-YenA2-YenB-YenC1-YenC2-Chi1-Chi2 (PubMed:21278295). The Yen-TC:K9 subcomplex is about 26 nm tall and 22 nm in diameter with 5-fold symmetry and 5 copies of YenA1, YenA2, Chi1 and Chi2; the chitinase subunits may be solvent accessible on the exterior the complex (PubMed:22158901). The Yen-TC:K9 subcomplex has no insecticidal activity (PubMed:22158901). The native complex with additional YenB, YenC1 and YenC2 subunits is 16 nm taller and is insecticidal; the toxicity-conferring subunits are present at about 1 copy each (PubMed:22158901). Secreted when grown at 25 degrees Celsius or less, but not when grown at 30 or 37 degrees Celsius. Cells with a disrupted yenA1-yenA2-chi2-yenB-yenC1-yenC2 locus are no longer pathogenic in C.zealandica larvae; chi1 was not tested. Belongs to the glycosyl hydrolase 18 family.