Pyruvate dehydrogenase E1 component subunit alpha, somatic form, mitochondrial is an enzyme that in humans is encoded by the PDHA1 gene.The pyruvate dehydrogenase complex is a nuclear-encoded mitochondrial matrix multienzyme complex that provides the primary link between glycolysis and the tricarboxylic acid (TCA) cycle by catalyzing the irreversible conversion of pyruvate into acetyl-CoA. The PDH complex is composed of multiple copies of 3 enzymes: E1 (PDHA1); dihydrolipoyl transacetylase (DLAT) (E2; EC 2.3.1.12); and dihydrolipoyl dehydrogenase (DLD) (E3; EC 1.8.1.4). The E1 enzyme is a heterotetramer of 2 alpha and 2 beta subunits. The E1-alpha subunit contains the E1 active site and plays a key role in the function of the PDH complex. Structure The PDHA1 gene has about 17 kilobase pairs; it contains 11 exons, which range from 61 to 174 base pairs, and introns, whose sizes range from 600 base pairs to 5.7 kilobase pairs. The splice donor and acceptor sites present within the gene all conform to GT/AC rule of splicing. The DNA sequence in the transcription initiation site is very GC-rich. There is a "TATA box"-like sequence and a "CAAT present upstream from the cap site. There are also several sets of repeats, sequences resembling the Sp1 transcription factor binding site, and two cAMP receptor binding sites upstream of the cap. The preliminary peptide encoded by this gene was 29 amino acids at the very start of the sequence that correspond to a typical mitochondrial targeting leader sequence. The remaining 361 amino acids, starting at the N terminus with phenylalanine, represent the mature mitochondrial E1 alpha peptide. Two of these mature PDHA proteins come together with two PDHB proteins to form a heterotetrameric E1 subunit. Crystal Structures allowed for a model in which the enzyme undergoes a 2-A shuttle-like motion of its heterodimers to perform the catalysis. The protein encoded by the human PDHA1 gene is part of the pyruvate dehydrogenase multienzyme complex. The entire human complex is 9.5 MDa in size, and has been described as 60-meric, meaning there are over 60 components that are assembled to make the entire complex. These subunits are conserved across many species, as the function of this complex is essential for the generation of ATP for all eukaryotes. Each component is responsible for the catalysis of one step in this pathway; this complex exists for the purpose of channeling the intermediates of each reaction to the next enzyme, thus greatly