Hydrolyzes deaminated glutathione (dGSH, 2-oxoglutaramate) to alpha-ketoglutarate (alpha-KG) and cysteinylglycine (specific activity 6.50 umol/min/mg), has less activity against alpha-ketoglutaramate (a-KGM, specific activity 0.20 umol/min/mg), very little activity on glutathione and none on L-glutamine. May function as a metabolite repair enzyme. H2O + N-(4-oxoglutaryl)-L-cysteinylglycine = 2-oxoglutarate + L-cysteinylglycine Belongs to the carbon-nitrogen hydrolase superfamily. NIT1/NIT2 family.