The biosynthesis and oxidation of ketone bodies

Acetoacetic acid, Acetone and beta-oxybutyric acid belong to ketone bodies. Their formation occurs in mitochondrions of hepatocytes only:

1) 2 acetylCoA are condensed into acetoacetylCoA;

2) acetoacetylCoA binds with acetylCoA giving beta-hydroxy-beta-methyl-glutarylCoA (HMG). The usage of this compound depends on expenditure of energy. If the energy needs, HMG is used for synthesis of ketone bodies. In hypodynamia HMG converts in cholesterol.

3) HMG is deacetylated to give acetoacetic acid (1-st ketone body). It is decarboxylated giving acetone (2-nd ketone body) or reduced to beta-hydroxybutyric acid (3-rd ketone body)

Acetoacetic and beta-oxybutyric acids are sources of energy. The oxidation of them occurs in muscular tissue and myocardium. But in starvation and diabetes mellitus ketone bodies are oxidized in brain too.

The oxidation of ketone bodies:

1) beta-oxybutyric acids is oxidized by HAD yielding acetoacetic acid

2) acetoacetic acid interacts with HSCoA giving acetoacetylCoA

3) acetoacetylCoA is splitted to 2 acetylCoA

4) each acetylCoA is oxidized in Crebs cycle giving 12 ATP (see the account of ATP through Crebs cycle in topic “Bioenergetics”. Thus, the oxidation of acetoacetic acid gives 24 ATP, and beta-hydroxybutyric acid – 27 ATP due to NADH2 forming in oxidation of beta-hydroxybutyryc acid

<== попередня сторінка	\|	наступна сторінка ==>
The biosynthesis of FFA	\|	The biosynthesis and metabolism of Cholesterol

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