Rapid loss of lactate dehydrogenase isoenzyme activity in serum by cold-induced formation of immunoglobulin G-lactate dehydrogenase complex.
Lactate dehydrogenase (LD; EC 1.1.1.27) activity in serum from a patient recovering from a myocardial infarction was extremely unstable when stored at 0 degree C. The activity of each LD isoenzyme except LD-1 decreased by at least 40% when serum was stored at 0 degree C for 4 h. The patient's erythrocyte LD activity had normal stability at lower temperatures, but LD from other sources, when added to the patient's serum, rapidly lost activity at 0 degree C. The patient's serum contained an immunoglobulin G that combined--at 0 degree C but not at 21 degrees C--primarily with LD isoenzymes containing one or more M subunits. Because this immunoglobulin-LD complex has no enzyme activity, we used 125I-labeled purified LD to study formation of the complex. NAD+ blocked the formation of immunoglobulin-LD complex but could not dissociate the complex and restore the LD activity.
D000818:Animals; D000936:Antigen-Antibody Complex / Q000302:isolation & purification*; D001345:Autoradiography; D055598:Chemical Phenomena; D002621:Chemistry; D003080:Cold Temperature; D006801:Humans; D005779:Immunodiffusion; D007122:Immunoelectrophoresis; D007074:Immunoglobulin G / Q000276:immunology*; D007527:Isoenzymes; D007770:L-Lactate Dehydrogenase / Q000097:blood* / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000276:immunology; D010215:Papio
D000936:Antigen-Antibody Complex; D007074:Immunoglobulin G; D007527:Isoenzymes; D007770:L-Lactate Dehydrogenase