Reconstitution of the electrophoretic complexity of mouse lactate dehydrogenase

Abstract

The residues which are covalently joined by disulphide bonds to mouse lactate dehydrogenase, and which affect the electrophoretic behaviour of the enzyme, have been isolated and identified as cysteine and glutathione. Oxidation of partially purified and previously reduced mouse muscle lactate dehydrogenase, in a solution containing a mixture of cysteine and glutathione, results in an electrophoretic pattern of the enzyme apparently identical with that of the native enzyme. The possibility that the polypeptide subunits of lactate dehydrogenase may exert a selective effect in their reactions with cysteine and reduced glutathione is discussed, and the likelihood that complex electrophoretic patterns of enzymes other than mouse lactate dehydrogenase may be caused by covalently bound simple metabolites is noted.