Phylogeny and ontogeny of the phosphoglycerate mutases—III. Inactivation of rabbit muscle phosphoglycerate mutase (type M isozyme) by the sulfhydryl group reagents

Abstract

1. 1. The three phosphoglycerate mutase isozymes from mammals (types M, B and MB isozymes) differ in their sensitivity to the —SH group reagents. 2. 2. Rabbit muscle phosphoglycerate mutase (type M isozyme) is reversibly inactivated by tetrathionate, p-chloromercuribenzoate and Hg 2+. 3. 3. Titration with p-chloromercuribenzoate shows the existence of two sulfhydryl groups per enzyme subunit, the modification of which produces a progressive decline in enzyme activity. 4. 4. The apparent K m values for substrate and cofactor are not affected by tetrathionate treatment. 5. 5. Phosphoglycerate mutase inactivated by tetrathionate and by p-chloromercuribenzoate is unable to form the functionally active phosphorylenzyme when mixed with glycerate-2,3-P 2, and is not protected by the cofactor against heating. 6. 6. Glycerate-2,3-P 2 protects against tetrathionate treatment, but fails to protect against Hg 2+ and p-chloromercuribenzoate inactivation.