THE PYRUVATE-DEHYDROGENASE MULTIENZYME COMPLEX FROM GRAM-NEGATIVE BACTERIA

Pyruvate dehydrogenase multi-enzyme complexes from Gram-negative bacte ria consists of three enzymes, pyruvate dehydrogenase/decarboxylase (E 1p), dihydrolipoyl acetyltransferase (E2p) and dihydrolipoyl dehydroge nase (E3). The acetyltransferase harbors all properties required for m ulti-enzyme catalysis: it forms a large core of 24 subunits, it contai ns multiple binding sites for the E1p and E3 components, the acetyltra nsferase catalytic site and mobile substrate carrying lipoyl domains t hat visit the active sites. Today, the Azotobacter vinelandii complex is the best understood oxo acid dehydrogenase complex with respect to structural details. A description of multi-enzyme catalysis starts wit h the structural and catalytic properties of the individual components of the complex. Integration of the individual properties is obtained by a description of how the many copies of the individual enzymes are arranged in the complex and how the lipoyl domains couple the activiti es of the respective active sites by way of flexible linkers. These la tter aspects are the most difficult to study and future research need to be aimed at these properties. (C) 1998 Elsevier Science B.V. All ri ghts reserved.