Jaburetox, a urease-derived peptide: Effects on enzymatic pathways of the cockroach Nauphoeta cinerea.

Jaburetox is a recombinant peptide derived from one of the Canavalia ensiformis urease isoforms. This peptide induces several toxic effects on insects of different orders, including interference on muscle contractility in cockroaches, modulation of UDP-N-acetylglucosamine pyrophosphorylase (UAP) and nitric oxide synthase (NOS) activities in the central nervous system of triatomines, as well as activation of the immune system in Rhodnius prolixus. When injected, the peptide is lethal for R. prolixus and Triatoma infestans. Here, we evaluated Jaburetox toxicity to Nauphoeta cinerea cockroaches, exploring the effects on the central nervous system through the activities of UAP, NOS, acid phosphatases (ACP), and acetylcholinesterase (AChE). The results indicated that N. cinerea is not susceptible to the lethal effect of the peptide. Moreover, both in vivo and in vitro treatments with Jaburetox inhibited NOS activity, without modifying the protein levels. No alterations on ACP activity were observed. In addition, the enzyme activity of UAP only had its activity affected at 18 hr after injection. The peptide increased the AChE activity, suggesting a mechanism involved in overcoming the toxic effects. In conclusion, our findings indicate that Jaburetox affects the nitrinergic signaling as well as the AChE and UAP activities and establishes N. cinerea as a Jaburetox-resistant model for future comparative studies.

ADP-glucose pyrophosphorylase from wheat endosperm. Purification and characterization of an enzyme with novel regulatory properties.

ADP-glucose pyrophosphorylase (AGPase; EC 2.7.7.27) was purified and characterized from two wheat (Triticum aestivum L.) tissues: leaf and endosperm. The leaf enzyme, purified over 1,300-fold, was found to be a heterotetramer composed of subunits of 51 and 54 kDa and possessing regulatory properties typical of AGPases from photosynthetic tissues, being mainly regulated by 3-phosphoglycerate (activator; A0.5=0.01 mM) and orthophosphate (inhibitor; I0.5=0.2 mM). Conversely, the enzyme from wheat endosperm was insensitive to activation by 3-phosphoglycerate and other metabolites. It was, however, inhibited by orthophosphate (I0.5=0.7 mM), ADP (I0.5=3.2 mM) and fructose-1,6-bisphosphate (0.5 = 1.5 mM). All of these inhibitory actions were reversed by 3-phosphoglycerate and fructose-6-phosphate. The endosperm enzyme was found to be a heterotetramer composed of subunits of 52 and 53 kDa, which were recognized by antiserum raised to spinach leaf AGPase. The results suggest that wheat endosperm AGPase possesses distinctive regulatory properties that are relevant in vivo.