Mitochondrial enzyme that catalyzes the dephosphorylation and concomitant reactivation of the alpha subunit of the E1 component of the pyruvate dehydrogenase complex (PDC), thereby stimulating the conversion of pyruvate into acetyl-CoA. {ECO:0000269|PubMed:15554715, ECO:0000305|PubMed:15855260}. This is the function of Ensembl gene identifier ENSG00000164951 (PDP1, pyruvate dehydrogenase phosphatase catalytic subunit 1).