Search PubMed⌕ Search

Biomedical subjects

B Mannervik

Publications and source records attributed to B Mannervik.

At least 271 records · Page 15Linked to original sources
PubMed1975

Purification and characterization of two glutathione S-aryltransferase activities from rat liver.

Two forms of glutathione S-aryltransferase were purified from rat liver. The only differences noted between the two forms were in the chromatographic and electrophoretic properties, which permitted the separation of the two species. The molecular weights of the enzyme and its subunits were estimated as about 50000 and 23000 respectively. The steady-state kinetics did no follow Michaelis-Menten kinetics when one substrate concentration was kept constant while the second substrate concentration was varied. Several S-substituted GSH derivatives were tested as inhibitors of the enzymic reaction. The enzyme was inactivated by thiol-group reagents.

Animals↗
PubMed1975

Reduction of disulphide bonds in proteins mixed disulphides catalysed by a thioltransferase in rat liver cytosol.

The reduction of mixed disulphides of some proteins and GSH [Protein(-SSG)n] is accomplished with GSH as a reductant and a thioltransferase from rat liver as a catalyst, thus: See article. The spontaneous reaction is negligible in comparison with the enzymic reaction in vivo, and any direct reduction with glutathione reductase is not detectable with the substrates used. The reduction is only indirectly dependent on NADPH, which is required for the regeneration of GSH from GSSG. Other protein disulphides apparently are reduced via analogous GSH-dependent reactions

Animals↗
PubMed1974

A steady-state kinetic model of butyrylcholinesterase from horse plasma.

The steady-state kinetics of the butyrylcholinesterase-catalysed hydrolysis of butyrylthiocholine and thiophenyl acetate were shown to deviate from Michaelis-Menten kinetics. The ;best' empirical rate law was selected by fitting different rate equations to the experimental data by non-linear regression methods. The results were analysed in view of two alternative interpretations: (1) the reaction is catalysed by a mixture of enzymes, or (2) the activity is due to a single enzyme displaying deviations from Michaelis-Menten kinetics. It was concluded that the second alternative applies, and this conclusion was further supported by experiments involving simultaneous hydrolysis of alternative thiol ester substrates (butyrylthiocholine/thiophenyl acetate) as well as alternative thiol ester and oxygen ester substrates (butyrylthiocholine/phenyl acetate; thiophenyl acetate/butyrylcholine; acetylthiocholine/phenyl acetate). On the basis of the conclusion that a single enzyme is responsible for the activity, a molecular model is proposed. This model involves an acylated enzyme, and implies binding to the enzyme of one acyl group and one ester molecule, but not two ester molecules at the same time. Thus butyrylcholinesterase, which is structurally a tetramer, behaves functionally as a co-operative dimer, an interpretation in accordance with available data from active-site titrations.

Animals↗