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Unformatted text preview: omplexes - why? Large protein machines are common: ribosome = 55 polypeptides DNA replication complex >20 polypeptides RNA transcriptional initiation complex spliceosome proteasome A multienzyme complex almost
identical to pyruvate
dehydrogenase Both use the same E3
polypeptide, different E1 and E2. "ome"= big complex 1. Can carry out a complex series of reactions. 2. Intermediates are channeled from one protein to the next. 3. Increase efficiency & speed, minimize side reactions. 15 16 Regulation of pyruvate dehydrogenase Regulation of the citric acid cycle. mainmly the regulation of materials Relatively simple: flux mainly determined by availability of substrates (acetyl CoA, NAD+, FAD). Acetyl CoA comes from e.g. pyruvate dehydrogenase Availability of NAD+ and FAD depends on their being regenerated by oxidative phosphorylation, whichrequires O2. Within the cycle a bit of regulation may occur? Only three non-equilibrium reactions: 1. citrate synthase 2. isocitrate dehydrogenase 3. α-ketoglutarate dehydrogenase There is currently little consensus on what the physiologically significant
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