Substrates of the five reactions catalyzed by pyruvate dehydrogenase complex are efficientl channeled The lipoamide group attached to e swings between E (accepting the electrons and acetyl group) and E, (giving away the electrons), passing the acetyl group to Coenzyme a on E The multienzyme complexes catalyzing the oxidative decarboxylation of a few different kinds of a-keto acids, pyruvate dehydrogenase complex, a ketoglutarate dehydrogenase complex and branched chain a-keto acid dehydrogenase complex show remarkable structure and function relatedness(all have identical E3, Similar El and E
• Substrates of the five reactions catalyzed by pyruvate dehydrogenase complex are efficiently channeled : The lipoamide group attached to E2 swings between E1 (accepting the electrons and acetyl group) and E3 (giving away the electrons), passing the acetyl group to Coenzyme A on E2 • The multienzyme complexes catalyzing the oxidative decarboxylation of a few different kinds of a-keto acids, pyruvate dehydrogenase complex, aketoglutarate dehydrogenase complex and branched chain a-keto acid dehydrogenase complex show remarkable structure and function relatedness (all have identical E3 , similar E1 and E2 )
CO 2 COA-SH NAD NADH TPP, lipoate O S-COA FAD C=0 C pyruvate dehydrogenase CH3 complex(E1+ E2+ E3) CH 3 Pyruvate Acetyl-CoA △G°′=-33.4kJ/mol The of pyruvate in mitochondria: producing acetyl-CoA and Co
The oxidative decarboxylation of pyruvate in mitochondria: producing acetyl-CoA and CO2
005pm Electron micrograph of teg from E coli
Electron micrograph of pyruvate dehydrogenase complexes from E. coli
pyruvate CO, acetvI-CoA E2(dihydrolipoyl transacetylase consisting the core, 24 subunits hydro TPP pyruvate dehydrogenase) bound to the E core, 24 subunits (dihydrolipoyl dehydrogenase) E 3 bound to the F, core, 12 subunit (a protein kinase and phosphoprotein phosphatase, not shown here, are also part of the comple apl e (b) A model of the E. coli complex showing the three kinds of enzymes and the flexible lipoamide arms covalently attached to F
A model of the E. coli pyruvate dehydrognase complex showing the three kinds of enzymes and the flexible lipoamide arms covalently attached to E2 E2 (dihydrolipoyl transacetylase): consisting the core, 24 subunits; E1 (pyruvate dehydrogenase): bound to the E2 core, 24 subunits; E3 (dihydrolipoyl dehydrogenase): bound to the E2 core, 12 subunits. (a protein kinase and phosphoprotein phosphatase, not shown here, are also part of the complex) pyruvate E2 E3 hydroxyethyl-TPP CO2 acetyl-CoA
The E core (a total of 24 subunits f orms a hollow cube X-ray structure of the E, transacetylase core. Onl four out of eight trimers are shown here
X-ray structure of the E2 transacetylase core: Only four out of eight trimers are shown here. The E2 core (a total of 24 subunits) forms a hollow cube