[Fatty acid synthases--strategic functions of multienzymes]

Several decades of biochemical research have led to our present detailed knowledge on cellular metabolism, is wealth of individual reactions, enzymes, and pathways, and their organization, interplay, and regulation. Although most metabolic reactions are simultaneous and occur in the same cell, they may also act independently of one other and without causing disturbing interferences. This demonstrates that the cellular interior is organized structurally and functionally and is not simply a "bag of enzymes." This organization ranges from distinct and functionally specialized organelles down to subtle or even hypothetical structures at the molecular level. The lowest level of structurally stable, supramolecular catalytic entities in the cell thus for known is that of the multienzyme complexes. Among the limited number of known multi-enzymes, fatty acid synthase is certainly one of the most complex and also best studied. Various structural and functional variants of this multienzyme system are known. These may be discussed in terms of specific requirements of the respective organisms.