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

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 Km 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.