Greater than 75% as determined by SDS-PAGE. Recombinant antigen for solid (ELISA) and fluid phase diagnostic assays. Mixture of E2/dihydrolipamide acyltransferase-subunits from 3 mitochondrial protein complexes: pyruvate dehydrogenase complex (PDC-E2) having a molecular mass of 60,630 Dalton (pI 5.8); 2-oxo-glutarate dehydrogenase complex (OGDC-E2) having a molecular mass of 42,301 Dalton (pI 6.3); branched chain 2-oxo-acid dehydrogenase complex (BCOADCE2) having a molecular mass of 47,321 Dalton (pI 6.5). Mixture contains equal mass of each protein component. cDNAs coding for the mature forms of the human PDC-E2, OGDC-E2 and BCOADC-E2 proteins individually fused to a hexa-histidine purification tag. M2 is supplied in 16mM HEPES buffer pH-8.0, 400mM NaCl, and 20% glycerol.Western blot with;anti-M2-Antigen autoantibody-positive patient sera or;monoclonal anti-hexa-His-tag antibody.;