Koike et al. (1988) cloned and sequenced cDNAs encoding the alpha and the beta subunits. Theoretically, there may be 2 forms of pyruvate dehydrogenase deficiency, one with mutation in the PDHA gene and one with mutation in the PDHB gene. Ho et al. (1988) isolated a 1.5-kb cDNA clone for the beta subunit of E1 from a human liver gamma-gt11 cDNA library using anti-E1 serum. Using a cDNA probe, Olson et al. (1990) demonstrated that the PHE1B gene is located on 3p13-q23. Koike et al. (1990) described the molecular cloning of the entire human PHE1B gene, its characterization by restriction enzyme analysis, and its complete nucleotide sequence. The gene is composed of 10 exons and 9 introns. All intron-exon splice junctions follow the GT/AG rule. The Alu family was found in introns 2 and 8.