CATALYTIC CENTERS IN THE THIAMIN DIPHOSPHATE DEPENDENT ENZYME PYRUVATE DECARBOXYLASE AT 2.4-ANGSTROM RESOLUTION

The crystal structure of brewers' yeast pyruvate decarboxylase, a thia min diphosphate dependent a-keto acid decarboxylase, has been determin ed to 2.4-angstrom resolution. The homotetrameric assembly contains tw o dimers, exhibiting strong intermonomer interactions within each dime r but more limited ones between dimers. Each monomeric subunit is part itioned into three structural domains, all folding according to a mixe d alpha/beta motif. Two of these domains are associated with cofactor binding, while the other is associated with substrate activation. The catalytic centers containing both thiamin diphosphate and Mg(II) are l ocated deep in the intermonomer interface within each dimer. Amino aci ds important in cofactor binding and likely to participate in catalysi s and substrate activation are identified.