Biological Characteristics of Recombinant Arthrobotrys oligospora Chitinase AO-801

Abstract

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>.