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Chitinase is an important virulence factor produced by nematode trapping fungi in the process of infection, and plays an important role in the cleavage of nematodes and their eggshells. In this study, the cDNA sequence of Arthrobotrys oligospora chitinase AO-379 was amplified by RT-PCR and inserted into the vector pPIC9K to induce the expression of AO-379 in Pichia pastoris GS115. The recombinant AO-379 (reAO-379) was purified by nickel ion affinity chromatography, and enzymological properties and nematode-degrading activity of reAO-379 was analyzed. SDS-PAGE and Western blot analysis showed that the reAO-379 with molecular weight of about 44 kDa was successfully obtained. The reAO-379 showed strong chitinase activity at pH 5.5 and 30°C. Using reAO-379 to treat Strongylus equinus, Caenorhabditis elegans and Haemonchus contortus for 12, 24, and 36 h , the killing rates of reAO-379 in S. equinus were 42%, 89% and 100%; in C. elegans were 50%, 90% and 97%; in and H. contortus were 53%, 62% and 84%, respectively. Using reA-379 to treat Fasciola hepatica and Dicrocoelium chinensis eggs for 24, 48 and 72 h, the degradation rates of reAO-379 were 12%, 43% and 65% in F. hepatica eggs, and were 15%, 33% and 55% in D. chinensis eggs, respectively. Our study suggests that the reAO-379 is potentially valuable for development of biological control agent against digestive tract nematodes in livestocks.

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Chitinase AO-801 is a hydrolase secreted by <i>Arthrobotrys oligospora</i> during nematode feeding, while its role remained elusive. This study analyzed the molecular characteristics of recombinant chitinase of <i>Arthrobotrys oligospora</i> (reAO-801). AO-801 belongs to the typical glycoside hydrolase 18 family with conserved chitinase sequence and tertiary structure of (α/β)₈ triose-phosphate isomerase (TIM) barrel. The molecular weight of reAO-801 was 42 kDa. reAO-801 effectively degraded colloidal and powdered chitin, egg lysate, and stage I larval lysate of <i>Caenorhabditis elegans</i>. The activity of reAO-801 reached its peak at 40˚C and pH values between 4-7. Enzyme activity was inhibited by Zn2⁺, Ca2⁺, and Fe3⁺, whereas Mg2⁺ and K⁺ potentiated its activity. In addition, urea, sodium dodecyl sulfate, and 2-mercaptoethanol significantly inhibited enzyme activity. reAO-801 showed complete nematicidal activity against <i>C. elegans</i> stage I larvae. reAO-801 broke down the <i>C. elegans</i> egg shells, causing them to die or die prematurely by hatching the eggs. It also invoked degradation of <i>Haemonchus contortus</i> eggs, resulting in apparent changes in the morphological structure. This study demonstrated the cytotoxic effect of reAO-801, which laid the foundation for further dissecting the mechanism of nematode infestation by <i>A. oligospora</i>.