Activation/inactivation of rat tissue pyroglutamate aminopeptidase by disulfide bond-reducing agents

The effects of dithiothreitol on pyroglutamate aminopeptidase activity in rat serum, spinal cord, brain, liver, kidney, and adrenal extracts were investigated in vitro. Addition of dithiothreitol to the reaction mixture resulted in noncompetitive inhibition of serum (Ki = 2.1 +/- 0.3 mM) and brain (Ki = 3.2 +/- 0.28 mM) enzymes and stimulation of liver, spinal cord, kidney and adrenal enzymes with an increase in Vmax but not Km. The findings of these studies suggest that the properties of Pyroglutamate aminopeptidases vary from tissue to tissue.