A multimer (24-mer or 60-mer, depending on the source) of this enzyme forms the core of the pyruvate dehydrogenase multienzyme complex, and binds tightly both EC
1.2.4.1, pyruvate dehydrogenase (acetyl-transferring) and EC
1.8.1.4, dihydrolipoyl dehydrogenase. The lipoyl group of this enzyme is reductively acetylated by EC
1.2.4.1, and the only observed direction catalysed by EC
2.3.1.12 is that where the acetyl group is passed to coenzyme A.