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The Department of Biochemistry of Medical Faculty. Presents now. ELONGATION, DESATURATION of FATTY ACIDS and FORMATION of ACTIVE MOLECULES. Edited by Attila Sandor. Mechanism of fatty acid elongation in animal cells. CH 3 -( CH2 ) 14 -CO-SCoA + OOC-CH 2 -CO-SCoA. acyl-CoA.

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The Department of Biochemistry

of Medical Faculty

Presents now

ELONGATION, DESATURATION of FATTY ACIDS

and FORMATION of ACTIVE MOLECULES

Edited by Attila Sandor


Mechanism of fatty acid elongation in animal cells

CH3-(CH2)14-CO-SCoA + OOC-CH2-CO-SCoA

acyl-CoA

malonyl-acyl-CoA

CO2

Elongation system located in the ER

HSCoA

CH3-(CH2)14-CO-CH2-CO-SCoA

2 NADPH2

H2O

Reduced to saturated C18 stearic acid

via three basic ezymes of fatty acid synthesis

Fatty acids are elongated on the head

Elongation system acts on CoA esters rather than on ACP-esters

Elongation system also uses malonyl-CoA as acceptor

Authors`picture


Mechanism of fatty acid desaruration in animal cells

O-O

4-

Belongs to the “mixed- function oxidases”, that is,

oxidases two substrate at the same time

Acts on CoA esters in the ER togethe with the Cyt b5 reductase

Intoduces duoble bonds before the 9th carbon atomin cis position

Lehn.,4th ed. 21-13 p. 799


Action of plant desaturases

The plant desaturases enzymes act on

fatty acid chains in phosholipids rather

than on CoA esters and introduce

double bounds before and after the 9th

carbon atom.

Lehn.,4th ed. 21-14 p. 800


Formation of the most important fatty acids

via combination of elongation and

desaturation

animals can put double bond only

before the 9th C atom

advantage of the w system:

after elongation the numbering does not turn upside down

w 6,9,12

w 6,9,12

w 6,9,12,15

Lehn.,4th ed. 21-12 p. 797


a

Strayer 3rd edition,20-19, p.490


CONCLUDING REMARKS

The overall equation of the synthesis of a palmitic acid :

7malonylCoA + 1AcCoA + 14 NADPH2 CH3-(CH2)14–COOH + 7 CO2 + 14NADP+ +6H2O + 8CoA

  • The fatty acids are elongated at the head by C2 untits

  • thus, the most fatty acids are even numbered.

  • The cytosolic fatty acid synthase enzyme synthetises

  • only palmitic acid.

  • The longer and/or unsaturated fatty acids are formed by

  • different microsomal enzymes

  • The odd-numbered fatty acids are synthtised when AT accepts

  • proponyl-CoA by mistake


Spliting sites of phospholipases

Lehn.,4th ed.10-15 p. 355


Source of arachidonic acid

Arachidonic acid (20:4, w 6,9,12,15) is the parenthal compound of many

biologically active fatty acid derivatives. It is located in membrane

phosholipids and released by phosholipase A2.

Steroids

Lehn.,4th ed. 10-18 p. 358


Biologically active derivatives of arachidonic acid

Anti-inflamatory drugs

inhibit:

Prostaglandins

Steroids:

Prostaglandins

Tromboxans

Leukotriens

Non-steroids:

Prostaglandins

Tromboxans

Steroids

Tromboxans

Aspirin

Cyclooxygenase

COX I,II

Lipoxygenase

Leukotriens

Unknown author


Lehn.,4th ed. p. 888

Steroids

Steroids inhibit:

Prostaglandins

Tromboxans

Leukotriens

Non-steroids (aspirin)

inhibit:

Tromboxans

Prostaglandins

Non-steroids

(aspirin)

lipoxygenase

Cyclooxygenane (COX I,II


Mechanism of action of non-steroid

(e.g.aspirin) anti-inflamatory drugs


Lehn.,4th ed. 21-15/b p. 801


Structure of Phosphatidic acid

Lehn.,4th ed.10-8 p. 350


Lehn.,4th ed.10-8 p. 350


Spliting by phospholipase C

Phosphatidyl-inositol 3 kinase

P I 3 K (enzyme)

Diacyl-glycerol,

DAG

Inositol 1,4,5, triphosphate

IP3

Phosphatidyl-inositol 3,4,5 trisphosphate,

PIP3

Two major roles of inositol-phosphates as second messengers

Phosphatidylinositol 4,5 bisphosphate,

PIP2

Author`s picture


Actions of IP3 and DAG

Lehn.,4th ed. 12-19, p. 443


PIP3 mediating the intracellular actions of insulin

Author`s

picture

IRS=insulin receptor substrate; GSK3=glycogen synthase kinase 3;

PKB/Akt= protein kinase B; GS= Glycogen synthase;


THANK YOU FOR YOUR ATTENTION

The honored audience has the opportunity now to

download

the pictures of this lecture

from here or from the intranet ActiveMoleculesfromFatty Acids.ppt

Attila Sandor


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