Inactivation of type MM phosphoglycerate mutase by sulfhydryl group reagents during facial embryogenesis

Abstract

Type MM phosphoglycerate mutase from free dissected mandibular processes from embryonic rats was reversibly inactivated by tetrathionate, p-chloromercuribenzoate, and Hg²⁺. Titration with p-chloromercuribenzoate showed the existence of two sulfhydryl groups per enzyme subunit, the modification of which produced a progressive decline in enzyme activity. The apparent K_m values for substrate and cofactor were not affected by tetrathionate treatment. Phosphoglycerate mutase inactivated by tetrathionate and by p-chloromercuribenzoate was unable to form the functionally active phosphorylenzyme when mixed with glycerate-2, 3-P₂. Glycerate-2, 3-P₂ protected against tetrathionate but failed to protect against Hg²⁺ and p-chloromercuribenzoate.