Interaction of thioredoxin with oxidized aminobutyrate aminotransferase. Evidence for the formation of a covalent intermediate.
Pig brain 4-aminobutyrate aminotransferase is inactivated by pre-incubation with pyrroloquinoline quinone (2,7,9-tricarboxy-1H-pyrrolo[2,3,f]quinoline- 4,5-dione; PQQ) at pH 7. The reaction of approximately 2 SH residues/dimer is sufficient to inactivate the enzyme. Reoxidized aminotransferase is reactivated by E. coli thioredoxin. Similar results were obtained with E. coli 4-aminobutyrate aminotransferase. The spectroscopic properties of thioredoxin, tagged with the fluorescence probe, anthraniloyl, were used to monitor its interaction with re-oxidized 4-aminobutyrate aminotransferase. During the regeneration of native aminotransferase by thioredoxin, the substrate forms a covalent intermediate with the oxidoreductase, as revealed by gel filtration chromatography. It is postulated that the substrate (oxidized aminotransferase) forms a covalent intermediate with thioredoxin through disulfide linkages.
Park
J
J
Department of Biochemistry, University of Tennessee, Knoxville 37996-0840.
Churchich
J E
JE
D000612:4-Aminobutyrate Transaminase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology; D004789:Enzyme Activation; D005456:Fluorescent Dyes; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology; D010084:Oxidation-Reduction; D013050:Spectrometry, Fluorescence; D013552:Swine; D013879:Thioredoxins / Q000378:metabolism*
D005456:Fluorescent Dyes; D013879:Thioredoxins; D000612:4-Aminobutyrate Transaminase