Inhibition of purified bovine liver glutathione reductase with some metal ions

Figures & data

Figure 1.  Inhibition of bovine liver GR by cadmium, nickel, and zinc ions.

Figure 2.  Lineweaver–Burk double reciprocal plot of initial velocity against GSSG as varied substrate and Cd²⁺ (0–0.25 mM) as inhibitor at fixed NADPH (0.1 mM) concentration. ▵ 0.1 mM NADPH (constant), ×0.1 mM Cd²⁺, ○ 0.125 mM Cd²⁺, ◊ 0.15 mM Cd²⁺, + 0.25 mM Cd²⁺.

Figure 3.  Lineweaver–Burk double reciprocal plot of initial velocity against NADPH as varied substrate and Cd²⁺ (0–0.25 mM) as inhibitor at fixed GSSG (0.7 mM) concentration. ▵ 0.7 mM GSSG (constant), ×0.1 mM Cd²⁺, ○ 0.125 mM Cd²⁺, ◊ 0.15 mM Cd²⁺, + 0.25 mM Cd²⁺.

Table 1.  Mechanism of inhibition of bovine liver GR by metal ions and Ki values.

Metal ion	Ki (mM)	Type of inhibition
Cadmium	KiGSSG 0.221 ± 0.02 mM	Non-competitive
	KiNADPH 0.113 ± 0.008 mM	Non-competitive
Nickel	KiGSSG 0.313 ± 0.01 mM	Non-competitive
	KiNADPH 0.932 ± 0.03 mM	Uncompetitive
Zinc	KiGSSG 0.320 ± 0.018 mM	Non-competitive
	KiNADPH 0.761 ± 0.04 mM	Non-competitive

Figure 4.  Lineweaver–Burk double reciprocal plot of initial velocity against GSSG as varied substrate and Ni²⁺ (0–0.6 mM) as inhibitor at fixed NADPH (0.1 mM) concentration. ▵ 0.1 mM NADPH (constant), ×0.1 mM Ni²⁺, ○ 0.2 mM Ni²⁺, ◊ 0.4 mM Ni²⁺, + 0.6 mM Ni²⁺.

Figure 5.  Lineweaver–Burk double reciprocal plot of initial velocity against NADPH as varied substrate and Ni²⁺ (0–0.6 mM) as inhibitor at fixed GSSG (0.7 mM) concentration. ▵ 0.7 mM GSSG (constant), × 0.1 mM Ni²⁺, ○ 0.2 mM Ni²⁺, ◊ 0.4 mM Ni²⁺, + 0.6 mM Ni²⁺.

Figure 6.  Lineweaver–Burk double reciprocal plot of initial velocity against GSSG as varied substrate and Zn²⁺ (0.1–0.4 mM) as inhibitor at fixed NADPH (0.1 mM) concentration. ▵ 0.1 mM NADPH (constant), × 0.1 mM Zn²⁺, ○ 0.2 mM Zn²⁺, ◊ 0.3 mM Zn²⁺, + 0.4 mM Zn²⁺.

Figure 7.  Lineweaver–Burk double reciprocal plot of initial velocity against NADPH as varied substrate and Zn²⁺ (0.1–0.4 mM) as inhibitor at fixed GSSG (0.7 mM) concentration. ▵ 0.7 mM GSSG (constant), × 0.1 mM Zn²⁺, ○ 0.2 mM Zn²⁺, ◊ 0.3 mM Zn²⁺, + 0.4 mM Zn²⁺.