Synthesis and evaluation of substrate analogue inhibitors of trypanothione reductase

Figures & data

Figure 1.  The reactions catalysed by trypanothione reductase and glutathione reductase.

Figure 2.  Inhibitors of trypanothione reductase.

Scheme 1.  Unsuccessful route to ester 13.

Scheme 2.  The synthesis of inhibitor 5.

Scheme 3.  The synthesis of inhibitors 3 and 4.

Table 1.  Inhibition of TR by compounds 3–5 and by previously reported inhibitors 6–9^a

Compound	Ki (µM)
3	2.0 ± 0.2
4	15.9 ± 1.5
5 ^Citation14	8.9 ± 0.9
6 ^Citation15	48 ± 3
7 ^Citation15	826 ± 76
8 ^Citation15	145 ± 24
9 ^Citation15	16 ± 2

^aAll assays were run using 29 as the TR substrate³⁰. Our determination of K_m for 29 was 6.7 µM (cf. trypanothione K_m = 50 µM²⁸). Kinetic constants were calculated using Cleland’s nonlinear least-squares program COMP³¹.

Figure 3.  TR assay substrate 29.

Figure 4.  Competitive inhibition of TR y 3–5. (a) Lineweaver–Burk (L–B) plot for TR inhibition in the absence (•) and presence of 3 at 2.2 µM (□), 5.1 µM (▴), 10.2 µM (◊), 15.3 µM (▪), and 19.7 µM (○). (b) L–B plot for TR inhibition in the absence (•) and presence of 4 at 18.7 µM (□), 62.5 µM (▴), and 109.3 µM. (c) L–B plot for TR inhibition in the absence (•) and presence of 5 at 15.3 µM (□), 61.1 µM (▴), 107.0 µM (◊), and 152.9 µM (▪). Each point represents the average of two to four experimental determinations; the lines are based on theoretical values derived from the nonlinear least-squares fit of the data sets using the COMP program ³¹.

Figure 5.  Potential electrophilic irreversible TR inhibitors.

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