What is a multi-enzyme complex

Multi-enzyme complex

Multi-enzyme complex, an ordered association of functionally and structurally different enzymes that catalyze successive steps in a reaction chain. The M. today known consist of 2-7 different, non-covalently linked, catalytic units (M.r 160 kDa to several million) that are not associated with lipids or nucleic acids and are free of enzymatically inactive protein material. They can be broken down into their still active half-molecules and partial enzymes or even into their (mostly inactive) subunits by changing pH, temperature and ionic strength, chemical modification or by treatment with neutral or anionic detergents. A reassociation of the dissociated M. to an active complex very similar to the physiological form has been described for many M. M. thus represent a much simpler, subcellular degree of compartmentalization than the membrane-bound enzymes associated with cell organelles (e.g. of the tricarboxylic acid cycle). Due to the close proximity of the active centers of the enzymes active in the M. as well as their high affinity for substrates and intermediates, the reactions are controlled, fast and without loss of substrate. The intermediates are transported directly from one enzyme to the next without dissociating from the complex. Examples of M. are the α-ketoglutarate dehydrogenase complex, the pyruvate dehydrogenase complex and the fatty acid synthetase complex.