LIPID METABOLISM

DR. MD. MAHBUBUR RAHMANMBBS, M. Phil, MSc. (Biotechnology)

ASSISTANT PROFESSOR

DEPT. OF BIOCHEMISTRY

RAJSHAHI MEDICAL COLLEGE

After the end of the session student will able to know the

• How fatty acid release from adipose tissue & their Fate

• Beta oxidation at a glance

• Mechanism of entry of LCFA

• Oxidation of Odd chain& unsaturated fatty acid

MOBILIZATION OF STORED FAT AND OXIDATION OF FATTY ACIDS

Release of Fatty acids from TAG

Activation of hormone sensitive lipase

Fate of glycerol

Fate of fatty acid

MOBILIZATION OF STORED FAT AND OXIDATION OF FATTY ACIDS

MOBILIZATION OF STORED FAT AND OXIDATION OF FATTY ACIDS

Fate of glycerol & fatty acid

In adipocyte there is lack of glycerol kinase.

Glycerol is transported through the blood to

the liver where it is phosphorylated. -------

then it is used to form TAG in the liver.

The fatty acid move through the cell membrane

of adipocyte and bind to albumin in the plasma.

Fate of glycerol & fatty acid

β oxidation of fatty acids

Compartment ---- Mitochondria.

Substrate – Fatty acid

Product – Acetyl coA

β oxidation of fatty acid

• Transport of long chain fatty (LCFA) acid into

mitochondria.

• Entry of short and medium chain fatty acids into the

mitochondria.

• Reaction of β oxidation

• Energy yields from fatty acid oxidation

• Oxidation of fatty acid with an odd

number of carbons.

β oxidation of fatty acid

Transport of long chain fatty (LCFA) acid into mitochondria

Transport of long chain fatty (LCFA) acid into mitochondria.

• Transport of fatty acids into the mitochondria

-----by carnitine shuttle mechanism.

• Carnitine serves as the carrier that transports

activated long chain fatty acyl groups across

the inner mitochondrial membrane.

Carnitine acyl transferase are able to transfer an

activaated fatty acyl group of CoA to the hydroxyl

group carnitine to form an acylcarnitine ester. This

reaction is reversible, so that the fatty acyl

co A derivatives can be regenerated from the

carnitine carrier.

Transport of long chain fatty (LCFA) acid into mitochondria.

Entry of short & medium chain fatty acid into mitochondria.

• Fatty acids shorter than twelve carbon can

cross the inner mitochondrial membrane

without the aid of carnitine or CPT system.

Beta oxidation

Energy production of complete oxidation of fatty acid

• Lipincott – 5th edition page 193

• Harper,s – 29th edition page 209

Oxidation of unsaturated FA

• In β oxidation of saturated fatty acids, a trans double bond is created between 2nd and 3rd carbon.

• For unsaturated fatty acid to undergo the βoxidation their cis bond is isomerised to trans double bond by trans enoyl co A isomerase.

Oxidation of a odd number FA

• At last of β oxidation of odd number fatty acid occur until three carbon (propynyl coA) residue.

• propynyl co A ----- methnoyl malonyl coA– then succynyl coA on of the intermediary product of TCA cycle ( Glucogenic)

Oxidation of fatty acids with odd number of C

Propionyl Co A MethylmalonylCo A

biotine dependend

Methylmalonyl Co A Succynyl CoA

Energy yields from fatty acid oxidation

• FAD bound acylcoA dehydrogenase

• NAD bound Hyddroxy acylcoA dehydrogenase.

Fate of Acetyl co A

• Oxidation through the TCA cycle

• Fatty acid synthesis

• Cholesterol synthesis

• Ketone Body synthesis

• Steroid hormone synthesis

• Synthesis of Bile salt.

Alternate route of fatty acid oxidation

• Peroxisomal oxidation

• ω- oxidation of fatty acids

Regulation of LCFA oxidation in Liver