Allosteric inhibition of carnosinase (CN1) by inducing a conformational shift

Figures & data

Figure 1. Dose-dependent effect of cysteine on recombinant CN1 activity. Levels of 0.2 mM cysteine and higher, resulted in significantly reduced CN1 activity (n = 8, p < .005).

Table 1. Catabolic rate of serum CN1 in the presence of inhibitors (n = 5).

	Vmax (µmol/mg/h)	Km (mM)	Efficiency (Vmax/Km)
Control	4.2 ± 0.4	0.8 ± 0.1	5.2 ± 0.2
Cysteine (1 mM)	1.8 ± 0.2*	1.0 ± 0.2	1.6 ± 0.2*
N-acetylcysteine (1 mM)	2.4 ± 0.2*	1.1 ± 0.3	2.0 ± 0.3*
GSH (1 mM)	2.9 ± 0.4*	0.9 ± 0.2	3.2 ± 0.4*
GSSG (1 mM)	4.1 ± 0.5	0.9 ± 0.3	4.6 ± 0.4
l-Glutamic acid (1 mM)	4.2 ± 0.5	0.8 ± 0.2	5.2 ± 0.3
Glycine (1 mM)	4.1 ± 0.4	0.7 ± 0.3	5.8 ± 0.4

Efficiency of recombinant CN1 activity were calculated by the ratio of V_max and K_m.

* p < .05 compared to control.

Figure 2. Dose-dependent effect of reduced glutathione (GSH) on renal CN1 activity of db/db mice and controls (at 25 weeks age). Addition of GSH, but not the addition of GSSG, reduced CN1 activity dose-dependently. 0.5 mM GSH significantly lowered CN1 activity for control and control mice (n = 8; p < .005).

Figure 3. Main interactions stabilized with carnosinase by: (A) carnosine within the catalytic pocket as computed by initial docking simulations; (B) Cys102-cysteinylated residue as derived at the end of the MD simulation; (C) Cys229-cysteinylated residue as derived at the end of the MD simulation.