Related Experiment Video
Updated: Aug 5, 2026

Sexual Transmission of American Trypanosomes from Males and Females to Naive Mates
Published on: January 27, 2019
[Inactivation of Trypanosoma cruzi trypanothione reductase by phenothiazine cationic free radicals]
J Gutierrez Correa1, A H Fairlamb, A O Stoppani
1Centro de Investigaciones Bioenergéticas, Facultad de Medicina (UBA-CONICET), Paraguay 2155, 1121 Buenos Aires, Argentina.
Abstract:
Peroxidase/H2O2/phenothiazine systems produced irreversible inhibition (inactivation) of Trypanosoma cruzi trypanothione reductase (TR). The enzyme inactivation depended on (a) the incubation time of TR with the peroxidase/H2O2/phenothiazine system; (b) the peroxidase nature and (c) the phenothiazine structure. With the more effective peroxidase/H2O2/phenothiazine systems, TR inactivation kinetics presented a relatively fast initial phase, lasting for about 10 min, in which most of the enzyme activity disappeared. This phase was followed by a slower one and, after 30 min incubation, TR was totally inactivated. Three peroxidases were assayed as catalysts of TR inactivation: the horseradish peroxidase (HRP), leukocyte myeloperoxidase (MPO) and modified myoglobin (Mb). Under comparable experimental conditions, the peroxidase system activity decreased in the given order. With HRP systems, 10 microM Thioridazine (TRDZ), Promazine (PZ), Trimeprazine (TMPZ), Prochlorperazine (PCZ), Propionylpromazine (PPZ), Chlorpromazine (CPZ) and Perphenazine (PFZ), produced 95-100% inactivation of TR. With the MPO/H2O2 systems, PZ. TRDZ and TMPZ were the most effective. Under similar experimental condition, the Mb/H2O2/PZ,/TMPZ, /TRDZ and CPZ systems effectively inactivated TR. The presence of alkylamino, piperazinyl, or piperidinyl groups in PTZ N atom (position 10) and -Cl, -CF3, -SCH3, COCH2CH3 and -CN in position C2 exerted significant influence on phenothiazine activity. Glutathione (GSH) prevented TR inactivation by the HRP/H2O2/PZ and MPO/H2O2/PZ systems. The HRP/H2O2 and MPO/H2O2/phenothiazines systems generated the corresponding cationic radicals (FTZ.+) the stability of which was limited by their conversion into phenothiazine-sulfoxides (PTZ-SO). The latter ones were inactive on TR. GSH rapidly reacted with PTZ+.; thus producing cation radical detoxication. These reactions fit in well with GSH protection of TR against the peroxidase/H2O2/phenothiazine system, as well as with the FTZ.+ role in phenothiazine cytotoxicity.
More Related Videos
Related Concept Videos
Bioactivation and Tissue Toxicity
Toxoplasmosis
American Trypanosomiasis
Anthelminthic Agents
Antiprotozoal Agents

