Allosteric Inhibition of Carnosinase (CN1) by Inducing a Conformational Shift

J Enzyme Inhib Med Chem. 2017 Dec;32(1):1102-1110. doi: 10.1080/14756366.2017.1355793.

Abstract

In humans, low serum carnosinase (CN1) activity protects patients with type 2 diabetes from diabetic nephropathy. We now characterized the interaction of thiol-containing compounds with CN1 cysteine residue at position 102, which is important for CN1 activity. Reduced glutathione (GSH), N-acetylcysteine and cysteine (3.2 ± 0.4, 2.0 ± 0.3, 1.6 ± 0.2 µmol/mg/h/mM; p < .05) lowered dose-dependently recombinant CN1 (rCN1) efficiency (5.2 ± 0.2 µmol/mg/h/mM) and normalized increased CN1 activity renal tissue samples of diabetic mice. Inhibition was allosteric. Substitution of rCN1 cysteine residues at position 102 (Mut1C102S) and 229 (Mut2C229S) revealed that only cysteine-102 is influenced by cysteinylation. Molecular dynamic simulation confirmed a conformational rearrangement of negatively charged residues surrounding the zinc ions causing a partial shift of the carnosine ammonium head and resulting in a less effective pose of the substrate within the catalytic cavity and decreased activity. Cysteine-compounds influence the dynamic behaviour of CN1 and therefore present a promising option for the treatment of diabetes.

Keywords: CN1; Carnosinase 1 activity; N-acetylcysteine; allosteric inhibition; diabetes; glutathione.

MeSH terms

  • Allosteric Regulation / drug effects
  • Dipeptidases / antagonists & inhibitors*
  • Dipeptidases / metabolism
  • Enzyme Inhibitors / chemistry
  • Enzyme Inhibitors / pharmacology*
  • Humans
  • Molecular Conformation
  • Molecular Dynamics Simulation
  • Sulfhydryl Compounds / chemistry
  • Sulfhydryl Compounds / pharmacology*

Substances

  • Enzyme Inhibitors
  • Sulfhydryl Compounds
  • CNDP1 protein, human
  • Dipeptidases

Grant support

This work was supported by the Deutsche Forschungsgemeinschaft [DFG; SFB 1118].