PURIFICATION AND PROPERTIES OF THIOL: PROTEIN DISULFIDE OXIDOREDUCTASE
Abstract
A membrane bound glycoprotein capable of catalyzing thiol:protein disulfide exchange has been purified from bovine and rat liver. The bovine enzyme is more nearly homogeneous, yet reveals minor microheterogeneity in isoelectric focusing and in the amino terminal sequence. The bovine and rat liver enzymes have physical characteristics similar to preparation of thiol:protein disulfied exchange activities from other laboratories. Immunological investigations indicate that their preparations contain enzymes homologous to those purified here. The isolated bovine liver enzyme has little substrate specificity, catalyzing the reactivation of scrambled ribonuclease as well as the reductive cleavage of insulin, utilizing a variety of thiol cosubstrates but not NADH or NADPH. Previous reports demonstrated that the rate of synthesis of an homologous enzyme in diabetic rat liver is regulated by plasma insulin concentration. The activity of an immunologically similar thiol:protein disulfide exchange activity in human fibroblast cultured in defined medium is here shown to vary with insulin concentration.
Degree
Ph.D.
Subject Area
Biochemistry
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