TY - JOUR
T1 - Relationship between the soluble glutathione dependent Δ5 3 ketosteroid isomerase and the glutathione S transferases of the liver
AU - Benson, A. M.
AU - Talalay, P.
AU - Keen, J. H.
AU - Jakoby, W. B.
PY - 1977
Y1 - 1977
N2 - Soluble, glutathione stimulated Δ5 3 ketosteroid isomerase (EC 5.3.3.1) activity of human and rat liver resides in very basic proteins with molecular weights of about 45,000 which are present in high concentrations in these tissues. Physicochemical and immunological evidence is presented for the identity of the proteins responsible for this enzymatic activity with the glutathione S transferases (RX:glutathione R transferase, EC 2.5.1.18) that conjugated glutathione with a variety of electrophilic compounds. In the rat, the steroid isomerase is associated principally with the major transferase (B), which is also known as ligandin, and has the versatility to bind various hydrophobic compounds such as bilirubin, corticosteroids, and metabolites of a number of carcinogens. Other rat liver glutathione S transferase species are far less active in the steroid isomerization reaction. The Δ5 3 ketosteroid isomerase activity of human liver is more uniformly distributed among the five glutathione S transferases that have been described. Steroid isomerization differs fundamentally from other reactions promoted by glutathione S transferases in that glutathione is not consumed in the reaction. However, because the transferase enzymes promote nucleophilic attack by glutathione on a variety of largely foreign organic substrates, a similar mechanism may be involved in the isomerase reaction. Δ5 3 ketosteroids are among the few known naturally occurring substrates for these enzymes.
AB - Soluble, glutathione stimulated Δ5 3 ketosteroid isomerase (EC 5.3.3.1) activity of human and rat liver resides in very basic proteins with molecular weights of about 45,000 which are present in high concentrations in these tissues. Physicochemical and immunological evidence is presented for the identity of the proteins responsible for this enzymatic activity with the glutathione S transferases (RX:glutathione R transferase, EC 2.5.1.18) that conjugated glutathione with a variety of electrophilic compounds. In the rat, the steroid isomerase is associated principally with the major transferase (B), which is also known as ligandin, and has the versatility to bind various hydrophobic compounds such as bilirubin, corticosteroids, and metabolites of a number of carcinogens. Other rat liver glutathione S transferase species are far less active in the steroid isomerization reaction. The Δ5 3 ketosteroid isomerase activity of human liver is more uniformly distributed among the five glutathione S transferases that have been described. Steroid isomerization differs fundamentally from other reactions promoted by glutathione S transferases in that glutathione is not consumed in the reaction. However, because the transferase enzymes promote nucleophilic attack by glutathione on a variety of largely foreign organic substrates, a similar mechanism may be involved in the isomerase reaction. Δ5 3 ketosteroids are among the few known naturally occurring substrates for these enzymes.
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U2 - 10.1073/pnas.74.1.158
DO - 10.1073/pnas.74.1.158
M3 - Article
C2 - 264670
AN - SCOPUS:0011852385
SN - 0027-8424
VL - 74
SP - 158
EP - 162
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 1
ER -