Isolation, purification, and characterization of a rat liver mitochondrial protein disulfide isomerase.

The isolation and purification to electrophoretical homogeneity and characterization of a protein disulfide isomerase from rat liver mitochondria is reported. The purified enzyme exhibits a single band on sodium dodecylsulfatepolyacrylamide gel electrophoresis with an apparent molecular weight of approximately 54 kDa. Comparatively, the microsomal form shows an apparent molecular weight of 57 kDa indicating that the two forms are slightly different. The antibody raised against the microsomal isoform does not recognize the mitochondrial enzyme. To characterize the enzyme, different classical methodologies utilized for protein disulfide isomerase estimation have been adopted. The isolated enzyme is active with all of them, indicating that it comprises all the features of a typical protein disulfide isomerase. At the mitochondrial level the enzyme appears mostly localized at the membrane level. Its potential involvement in mitochondrial membrane permeability control is also discussed.