TY - JOUR
T1 - Differential susceptibility of filarial and human erythrocyte glutathione reductase to inhibition by the trivalent organic arsenical melarsen oxide
AU - Müller, Sylke
AU - Walter, Rolf D.
AU - Fairlamb, Alan H.
N1 - Funding Information:
The authors like to thank Dr. K. Smith and Mr. M. Cunningham for their support. Further we like to thank Dr. P. Kaye for his help to raise the anti-GR-antiserum.T his study was supportedb y a Travelling Fellowship from the Wellcome Trust and by the Deutsche Forschungsgemeinschaft WA 395/8 (S.M.).
PY - 1995/5
Y1 - 1995/5
N2 - The glutathione reductases (GR) from two cattle filariae (Setaria digitata and Onchocerca gutturosa) have been isolated and their properties have been compared to those of human erythrocyte GR. In general, the enzymes appear to be very similar with respect to substrate-specificity for glutathione disulfide and NADPH, molecular mass (97 kDa vs. 98 kDa) and oligomeric organisation (subunit size of 51 kDa vs. 50 kDa). However, studies on the inhibition of the enzymes by the trivalent melaminophenyl arsenical melarsen oxide revealed that the human GR is less susceptible to inhibition by the arsenical than the filarial enzymes. Further, it was found that the mechanism of inactivation differs for the host and filarial enzymes. The human enzyme is inhibited by melarsen oxide in a competitive manner with a Ki of 23.7 μM, whereas the filarial GRs are inhibited in two stages: an immediate partial inactivation followed by a time-dependent stage with saturable pseudo-first-order kinetics. Ki values for the S. digitata and O. gutturosa GRs are 38.3 μM and 4.5 μM, respectively, with maximum second-stage inactivation rates of 1.0 × 10-4 s-1 and 24.3 × 10-4 s-1, respectively. These differences between host and parasite enzyme might reflect differences in the primary and secondary structure of the proteins which might be exploitable for the design of new specific macrofilaricidal drugs.
AB - The glutathione reductases (GR) from two cattle filariae (Setaria digitata and Onchocerca gutturosa) have been isolated and their properties have been compared to those of human erythrocyte GR. In general, the enzymes appear to be very similar with respect to substrate-specificity for glutathione disulfide and NADPH, molecular mass (97 kDa vs. 98 kDa) and oligomeric organisation (subunit size of 51 kDa vs. 50 kDa). However, studies on the inhibition of the enzymes by the trivalent melaminophenyl arsenical melarsen oxide revealed that the human GR is less susceptible to inhibition by the arsenical than the filarial enzymes. Further, it was found that the mechanism of inactivation differs for the host and filarial enzymes. The human enzyme is inhibited by melarsen oxide in a competitive manner with a Ki of 23.7 μM, whereas the filarial GRs are inhibited in two stages: an immediate partial inactivation followed by a time-dependent stage with saturable pseudo-first-order kinetics. Ki values for the S. digitata and O. gutturosa GRs are 38.3 μM and 4.5 μM, respectively, with maximum second-stage inactivation rates of 1.0 × 10-4 s-1 and 24.3 × 10-4 s-1, respectively. These differences between host and parasite enzyme might reflect differences in the primary and secondary structure of the proteins which might be exploitable for the design of new specific macrofilaricidal drugs.
KW - Arsenical drug
KW - Chemotherapy
KW - Filariasis
KW - Glutathione reductase
UR - http://www.scopus.com/inward/record.url?scp=0029026498&partnerID=8YFLogxK
U2 - 10.1016/0166-6851(94)00053-P
DO - 10.1016/0166-6851(94)00053-P
M3 - Article
C2 - 7477103
AN - SCOPUS:0029026498
SN - 0166-6851
VL - 71
SP - 211
EP - 219
JO - Molecular and Biochemical Parasitology
JF - Molecular and Biochemical Parasitology
IS - 2
ER -