Ketogenesis — four mitochondrial enzymes, liver teaching set
Two acetyl-CoA units become acetoacetate and D-β-hydroxybutyrate. HMGCS2 is the committed mitochondrial synthase (cytosolic HMGCS1 is cholesterol, not this path). Acetone from spontaneous decarboxylation is not a page.
Mitochondrial acetoacetyl-CoA thiolase ACAT1 · T2
2 acetyl-CoA → acetoacetyl-CoA + CoA
Condensation on 2IBY. Occupancy is free CoA, not acetyl-CoA. Cys126 is CSO on this crystal. Not ACAA2 (T1). Ketolysis uses a separate page.
EC 2.3.1.9 · PDB 2IBY
▶ OPEN SIMULATORMitochondrial HMG-CoA synthase HMGCS2
acetoacetyl-CoA + acetyl-CoA + H₂O → HMG-CoA + CoA
Committed condensation on 2WYA. Occupancy is product HMG-CoA, not the two acyl-CoA substrates. Cys166 is the nucleophile. Not cytosolic HMGCS1.
EC 2.3.3.10 · PDB 2WYA
▶ OPEN SIMULATORMitochondrial HMG-CoA lyase HMGCL
(3S)-HMG-CoA → acetoacetate + acetyl-CoA
Lyase on 3MP5 chain B. Occupancy is substrate HMG-CoA + Mg. 3MP5 is R41M — Arg41 is not this mesh. His233 is a Mg ligand only, not the general base.
EC 4.1.3.4 · PDB 3MP5
▶ OPEN SIMULATORD-β-hydroxybutyrate dehydrogenase BDH1
acetoacetate + NADH + H⁺ → D-β-hydroxybutyrate + NAD⁺
Reduction on A. faecalis 3W8E — human BDH1 has no PDB. Occupancy is NAD⁺ + D-BHB (products), not acetoacetate. Not HADH (opposite stereo, CoA thioester).
EC 1.1.1.30 · PDB 3W8E
▶ OPEN SIMULATOR