Exploring Spiders Without Venom as New Sources of Peptidase Inhibitors

Peptidases constitute at least 2% of genes in living organisms and participate in nearly all physiological processes across life forms. Conversely, peptidase inhibitors are essential for regulating proteolytic activity and have been widely applied. Combining high-throughput sequencing of novel peptidase inhibitor sources with molecular modeling and drug design currently represents an efficient strategy for developing new molecules. Venomous spiders harbor a wide array of peptidase inhibitors in both their venom and digestive system. However, biochemical and transcriptomic investigations of non-venomous spiders (Uloboridae) remain recent and scarce. Here, transcriptomic and biochemical analyses of the Uloboridae spider <i>Zosis geniculata</i>'s digestive midgut diverticula (MD) revealed that this species exhibited a digestive enzyme profile similar to that of other spiders. Furthermore, the MD transcriptome identified 19 peptidase inhibitors belonging to six inhibitor families. Serine peptidase inhibitors were the most abundant and diverse, while metallopeptidases represented the main proteolytic enzymes, suggesting that these inhibitors may have evolved to counteract prey-derived peptidases. Inhibitory assays using trypsin from potential insect prey confirmed this activity. The diversity and abundance of these molecules highlight Uloboridae spiders as promising novel sources of proteolytic inhibitors.