Function of several critical amino acids in human pyruvate dehydrogenase revealed by its structure

Pyruvate dehydrogenase (E1), an α2β2 tetramer, catalyzes the oxidative decarboxylation of pyruvate and reductive acetylation of lipoyl moieties of the dihydrolipoamide acetyltransferase. The roles of βW135, αP188, αM181, αH15, and αR349 of E1 determined by kinetic analysis were reassessed by analyzing the three-dimensional structure of human E1. The residues identified above are found to play a structural role rather than being directly involved in catalysis: βW135 is in the center of the hydrophobic interaction between β and β′ subunits; αP188 and αM181 are critical for the conformation of the TPP-binding motif and interaction between α and β subunits; αH15 is necessary for the organization of the N-terminus of α and α′ subunits; and αR349 supports the interaction of the C-terminus of the α subunits with the β subunits. Analysis of several critical E1 residues confirms the importance of residues distant from the active site for subunit interactions and enzyme function.