An Electrochemical Approach to Follow and Evaluate the Kinetic Catalysis of Ricin on hsDNA.

George Oliveira,José Maurício Schneedorf

doi:10.3390/life11050405

Abstract

International authorities classify the ricin toxin, present in castor seeds, as a potential agent for use in bioterrorism. Therefore, the detection, identification, and characterization of ricin are considered the first actions for its risk assessment during a suspected exposure, parallel to the development of therapeutic and medical countermeasures. In this study, we report the kinetic analysis of electro-oxidation of adenine released from hsDNA by the catalytic action of ricin by square wave voltammetry. The results suggest that ricin-mediated adenine release exhibited an unusual kinetic profile, with a progress curve controlled by the accumulation of the product and the values of the kinetic constants of 46.6 µM for Km and 2000 min−1 for kcat, leading to a catalytic efficiency of 7.1 × 105 s−1 M−1.

Highlights

Ricin, found in the endosperm of castor seeds (Ricinus communis L.), is considered one of the most potent toxins of plant origin, with a lethal LD50 of only 5 μg/kg in mice, with the symptoms appearing up to 4 h after inhalation and the irreversibility of the lethal condition between 6 to 12 h [1,2]
IC50 values determined from these experiments suggest that inhibition by adenine has a significant effect during in vitro assays (Figure 2a)
Our findings rev vealed that the ricin catalysis can be determined amperometrically

Summary

Introduction

Found in the endosperm of castor seeds (Ricinus communis L.), is considered one of the most potent toxins of plant origin, with a lethal LD50 of only 5 μg/kg in mice (inhalation), with the symptoms appearing up to 4 h after inhalation and the irreversibility of the lethal condition between 6 to 12 h [1,2]. Its action mechanism involves the inactivation of protein synthesis by an N-glycosilase activity towards a specific adenine residue in ribosomal DNA. Ricin has gained recent attention from governments and the international scientific community due to its potential use in bioterrorism, the low cost for plant cultivation, the relative simplicity for extraction, and a good stability of the phytotoxin [3,4]. In this context, ricin is classified by the US Centers for Disease Control and Prevention (CDC, Atlanta, GA, United States) as a category B bioterrorism agent [5,6]. The RTA subunit acts as a ribosome inactivator type II (RIP), causing cell death by the depurination of the adenine

Methods

Discussion

Conclusion