The Department of Biochemistryof Medical Faculty

Presents now

Edited by Attila Sandor

SYNTHESIS of CHOLESTEROL and KETONE BODIES

Classification of lipids on chemical basis

Fatty acid derivatives IsoprenoidsSimple lipids Complex lipids

TriglyceridsVaxes

PhospholipidsGlycolipids

SteroidsCarotinoids

Author`s picture

A C5 hydrocarbon occurring in oil but not in living organisms

Lehn. 4th ed., p.816

The way of isoprenoid synthesis (1)

an enzyme of-oxidation C2+C2 = C4

The way of isoprenoid synthesis (2)

C4+C2 = C6

The way of isoprenoid synthesis (3)

to ketone bodies

C6

C6

C6

C6C6-C=C5

C6

The way of isoprenoid synthesis (4)Formation of the final C5 unit

The action of C15 prenyltransferase (3 X 5)

C5

C15

C10

The action of C15 squalene synthase (2 X 15)

Strayer 5th ed. 26.10, p724

Formation of Squalene (2 X 15 = 30), still straight skeleton

Head to Head

Cholesterol

-3CSqualene Lanosterol

Formation of cyclised C30 lanosterol, theimmediate precursor of cholesterol

Cholesterol C27

-3C

(6C X 5C)-3C = 27C, ring 17C + 2C methyl + 8C side chain

Structure, nubering and origins of atoms of cholesterol

Strayer, 5th ed. 26.25 p.733

Chlesterol may be esterified with fatty acids

Lehn., 4th ed. Fig. 21-38, p.820

polyprenyltransferase

C15 prenyltransferase

C20 prenyltransferase

Compounds built from C5 isoprenoid blocks

Lehn., 4th ed. Fig. 21-48, p.828

The way of isoprenoid synthesis (3)

to ketone bodies

C6

C6

HMG-CoA is a branchpoint

Cleavage enzyme

Reductase

HMG-CoA synthase

Ketone bodies

Cholesterol

Strayer, 5th ed. 26.7 p.723

The two ketone bodies are interchangable

The activation of acetoacetate for the metabolism

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Attila Sandor

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