Plant Ureases and Related Peptides: Understanding Their Entomotoxic Properties

Abstract

Recently, ureases were included in the arsenal of plant defense proteins, alongside many other proteins with biotechnological potential such as insecticides. Isoforms of Canavalia ensiformis urease (canatoxin—CNTX and jack bean urease—JBURE-I) are toxic to insects of different orders. This toxicity is due in part to the release of a 10 kDa peptide from the native protein, by cathepsin-like enzymes present in the insect digestive tract. The entomotoxic peptide, Jaburetox-2Ec, exhibits potent insecticidal activity against several insects, including many resistant to the native ureases. JBURE-I and Jaburetox-2Ec cause major alterations of post-feeding physiological processes in insects, which contribute to, or can be the cause of, their entomotoxic effect. An overview of the current knowledge on plant urease processing and mechanisms of action in insects is presented in this review.

Central and peripheral neurotoxicity induced by the Jack Bean Urease (JBU) in Nauphoeta cinerea cockroaches

“…In previous studies, we reported that the lethality of Jack Bean ureases given orally to insects depends on characteristics of their digestive system (Stanisçuaski and Carlini, 2012). At least part of the insecticidal effect is caused by toxic peptides derived from ureases upon cleavage by insect's digestive enzymes.…”

“…Although JBU has been proven to be insecticidal to different insects (Stanisçuaski and Carlini, 2012), it displayed no lethality in Nauphoeta cinerea cockroaches, at least not by intrabdominal administration in a 24 hours observation time. In previous studies, we reported that the lethality of Jack Bean ureases given orally to insects depends on characteristics of their digestive system (Stanisçuaski and Carlini, 2012).…”

“…Canavalia ensiformis displays several urease isoforms: the most abundant one Jack Bean Urease (JBU) (Sumner, 1926), canatoxin (CNTX) (Carlini and Guimarães, 1981;Follmer et al, 2001) and JBURE-II (Mulinari et al, 2011;Pires-Alves et al, 2003). The entomotoxic action of C. ensiformis ureases has been shown in different insect models (Stanisçuaski and Carlini, 2012). Afterwards, a recombinant peptide named Jaburetox, derived from the urease isoform JBURE-II of C. ensiformis, was produced in Escherichia coli and its direct paralyzing effect on the cockroach neuromuscular junction was reported .…”

“…The growing knowledge on the non-enzymatic properties of ureases, plant proteins crucial for the conversion of urea to ammonia, has unveiled their potential as biological insecticides (Carlini and Ligabue-Braun, 2016;Stanisçuaski and Carlini, 2012). Ureases (EC 3.5.1.5, urea amidohydrolase) are nickel-dependent metalloenzymes (Dixon et al, 1975) that catalyze the conversion of urea to two molecules of ammonia and one of carbon dioxide, enhancing the rate of the uncatalyzed hydrolysis by a factor of 8×10 17 (Callahan et al, 2005).…”

Soybean Urease: Over a Hundred Years of Knowledge

“…For the jackbean ureases, it has been demonstrated that this entomotoxic effect is a highly complex event, involving the intact protein as well as the release of a toxic peptide [82,89,90]. Jackbean ureases and their derived peptides affect several physiological processes in the insects, including the fluid transport across membranes [83,91,92]. So far, no studies regarding es-SBU mechanism of action in insects were performed, but it reasonable to assume that, due to their very similar sequences (92% of similarity), es-SBU and JBU would have the same targets in these organisms.…”