PubMed Health⌕ Search

Biomedical subjects

W B Jakoby

Publications and source records attributed to W B Jakoby.

At least 55 records · Page 3Linked to original sources
PubMed1981

Sulfate transfer to thyroid hormones and their analogs by hepatic aryl sulfotransferases.

The transfer of sulfate to thyroid hormones and their analogs by a monkey hepatocarcinoma cell extract was compared to this reaction as catalyzed by two homogeneous aryl sulfotransferases from rat liver. The thyroid hormones 3,5,3'-triiodo-L-thyronine and L-T4 as well as analogs of these hormones, were used as substrates. While these compounds vary widely in their capacity as sulfate acceptors, the catalytic abilities of the three enzyme preparations generally reflect a broad pattern of overlapping specificity. The finding that T4 is a very poor substrate, that 3'-iodothyronine and 3,3'-diiodothyronine are very good substrates, and that T3 is intermediate in its acceptor activity probably explains the relative sulfation of these compounds in vivo and by living hepatocytes. (Endocrinology 108: 454, 1981)

Animals↗
PubMed1979

Phenol sulfotransferases.

Two phenol sulfotransferases have been purified from rat liver by conventional techniques coupled with affinity chromatography on Affi-Gel blue and ATP-agarose. Both enzymes are homogeneous by the criterion of sodium dodecyl sulfate gel electrophoresis. Each enzyme has a molecular weight of approximately 65,000 and consists of two subunits of apparently equal size. The enzymes are also similar in specificity and in their kinetic parameters but differ in amino acid composition and in their elution from DEAE-cellulose. With adenosine 3'-phosphate 5'-phosphosulfate as donor, a large variety of phenolic compounds serve as sulfate acceptor; sterols, simple alcohols, bile acids, and hydroxamates do not serve as substrates. The transferases may be considered as detoxification enzymes which catalyze the conjugation of xenobiotics containing a phenol group or of phenolic compounds generated by endogenous oxidation. The enzymes act on 3-hydroxyindole to yield indican, suggesting that their in vivo function may include the production of this normal tryptophan metabolite.

Amino Acids↗
PubMed1978

Glutathione transferases. Catalysis of nucleophilic reactions of glutathione.

Homogeneous preparations of the glutathione transferases from rat liver have been tested for their ability to catalyze a number of diverse nucleophilic reactions of GSH. Although disulfide interchange with GSSG or L-cystine, and cis-trans isomerization of maleic acid, are clearly promoted by thiols in solution, the reactions were not catalyzed by the glutathione transferases. In contrast, certain more hydrophobic analogs of these compounds were found to serve as substrates. The transferases also catalyze the glutathione-dependent release of p-nitrophenol from p-nitrophenyl acetate and p-nitrophenyl trimethylacetate. These observations are consistent with the formulation that catalysis may result from close juxtaposition of sufficiently electrophilic, nonpolar compounds with GSH on the enzyme surface.

Animals↗