multienzymkomplex

Multienzymkomplex, or multienzyme complex, is a molecular assembly composed of several enzymes that catalyze consecutive steps within a metabolic pathway. These complexes can be highly stable, with enzymes linked on a single scaffold through protein-protein interactions, or dynamic and transient, forming metabolons that assemble and disassemble as needed. By bringing enzymatic activities into close proximity, multienzymkomplexes facilitate substrate channeling, increase reaction throughput, coordinate regulation of pathway flux, and reduce diffusion of labile intermediates. They may also enable shared cofactors and streamlined control of metabolic steps.

Organizationally, multienzymkomplexes can be categorized as stable scaffolded assemblies or transient metabolons. Some are membrane-bound or localized to specific organelles, while others exist in the cytosol. Regulatory mechanisms include phosphorylation, allosteric control, and regulated assembly or disassembly in response to cellular signals. The architecture is often modular, with catalytic domains aligned to optimize sequence of reactions and cofactor reuse.

Prominent examples include the pyruvate dehydrogenase complex in mitochondria, which couples pyruvate decarboxylation to acetyl-CoA formation and NADH production; fatty acid synthase (type I) in animals, a megaenzyme containing multiple catalytic activities within a single polypeptide; and the glycine cleavage system in mitochondria, a multi-enzyme complex that degrades glycine. In bacteria and fungi, modular megasynthases such as polyketide synthases also function as multienzymatic assemblies.

Multienzymkomplexes are relevant for metabolism, cellular regulation, and metabolic engineering. Disruptions can contribute to metabolic disorders, while engineered complexes offer potential for increased pathway efficiency and novel biosynthetic capabilities.