Biochem - Bridge Reaction

Step 1: decarboxylation

1 pyruvate + 1 thiamine pyrophosphate = 1 hydroxyethyl-TPP + CO2

E1: pyruvate dehydrogenase

Step 2: oxidation

1 hydroxyethyl-TPP + 1 lipoamide swinging arm = 1 reduced lipoamide swinging arm with bound acetyl group formed from the oxidized hydroxyethyl group

E2: dihydrolipoamide transacetylase

Step 3: formation of Acetyl-CoA

1 reduced lipoamide swinging arm with bound acetyl group + 1 CoA-SH = 1 dihydrolipoamide swinging arm + 1 acetyl-CoA

E2: dihydrolipoamide transacetylase

Step 4: reoxidation of swinging arm

1 dihydrolipoamide swinging arm + 1 FAD-S-S = 1 oxidized lipoamide swinging arm + 1 FAD-SH-SH

E3: dihydrolipoamide dehydrogenase

Step 5a: FAD as intermediate electron carrier

1 FAD-SH-SH = 1 FADH2-S-S

E2: dihydrolipoamide dehydrogenase

Step 5b: Reduction of NAD+

1 FADH2-S-S + 1 NAD+ = 1 FAD-S-S + 1 NADH and H+

E2: dihydrolipoamide dehydrogenase