Trypanosoma cruzi trypanothione reductase is inactivated by peroxidase-generated phenothiazine cationic radicals

TY - JOUR

T1 - Trypanosoma cruzi trypanothione reductase is inactivated by peroxidase-generated phenothiazine cationic radicals

AU - Gutierrez-Correa, Jose

AU - Fairlamb, Alan

AU - Stoppani, Andres O.M.

N1 - Funding Information: This work was aided by grants from the University of Buenos Aires and the Roemmers Foundation. We are grateful to Mr A. Boveris (School of Pharmacy and Biochemistry, University of Buenos Aires) for the ESR measurements, and to M.G. Guti6rrez and M.A. Ver6n for useful technical assistance.

PY - 2001

Y1 - 2001

N2 - Trypanosoma cruzi trypanothione reductase (TR) was irreversibly inhibited by peroxidase/H2O2/phenothiazine (PTZ) systems. TR inactivation depended on (a) time of incubation with the phenothiazine system; (b) the peroxidase nature and (c) the PTZ structure and concentration. With the most effective systems, TR inactivation kinetics were biphasic, with a relatively fast initial phase during which about 75% of the enzyme activity was lost, followed by a slower phase leading to total enzyme inactivation. GSH prevented TR inactivation by the peroxidase/H2O2/PTZ+ systems. Production of PTZ+ cation radicals by PTZ peroxidation was essential for TR inactivation. Horseradish peroxidase, leukocyte myeloperoxidase (MPO) and the pseudo-peroxidase myoglobin (Mb) were effective catalysts of PTZ+ production. Promazine, thioridazine, chlorpromazine, propionylpromazine prochlorperazine, perpenazine and trimeprazine were effective constituents of the HRP/H2O2/PTZ system. The presence of substituents at the PTZ nucleus position 2 exerted significant influence on PTZ activity, as shown by the different effects of 2-trifluoromethyl and 2-H or 2-chlorophenothiazines. The PTZ+ cation radicals disproportionation regenerated the non-radical PTZ molecule and produced the PTZ sulfoxide that was inactive on TR. Thiol compounds including GSH interacted with PTZ+ cation radicals transferring an electron from the sulfide anion to the PTZ+, thus nullifying the PTZ+ biological and chemical activities.

AB - Trypanosoma cruzi trypanothione reductase (TR) was irreversibly inhibited by peroxidase/H2O2/phenothiazine (PTZ) systems. TR inactivation depended on (a) time of incubation with the phenothiazine system; (b) the peroxidase nature and (c) the PTZ structure and concentration. With the most effective systems, TR inactivation kinetics were biphasic, with a relatively fast initial phase during which about 75% of the enzyme activity was lost, followed by a slower phase leading to total enzyme inactivation. GSH prevented TR inactivation by the peroxidase/H2O2/PTZ+ systems. Production of PTZ+ cation radicals by PTZ peroxidation was essential for TR inactivation. Horseradish peroxidase, leukocyte myeloperoxidase (MPO) and the pseudo-peroxidase myoglobin (Mb) were effective catalysts of PTZ+ production. Promazine, thioridazine, chlorpromazine, propionylpromazine prochlorperazine, perpenazine and trimeprazine were effective constituents of the HRP/H2O2/PTZ system. The presence of substituents at the PTZ nucleus position 2 exerted significant influence on PTZ activity, as shown by the different effects of 2-trifluoromethyl and 2-H or 2-chlorophenothiazines. The PTZ+ cation radicals disproportionation regenerated the non-radical PTZ molecule and produced the PTZ sulfoxide that was inactive on TR. Thiol compounds including GSH interacted with PTZ+ cation radicals transferring an electron from the sulfide anion to the PTZ+, thus nullifying the PTZ+ biological and chemical activities.

KW - Cationic radicals

KW - Horseradish peroxidase

KW - Myeloperoxidase

KW - Myoglobin

KW - Phenothiazine

KW - Trypanothione reductase

UR - https://www.scopus.com/pages/publications/0035057943

U2 - 10.1080/10715760100300311

DO - 10.1080/10715760100300311

M3 - Article

C2 - 11328673

AN - SCOPUS:0035057943

SN - 1071-5762

VL - 34

SP - 363

EP - 378

JO - Free Radical Research

JF - Free Radical Research

IS - 4

ER -