Biochemistry from Dr. Dhiraj J. Trivedi SDM College of Medical Sciences and Hospital, Dharwad, India

1. Elongation of Fatty Acids

2. Elongation of Fatty Acids
 Addition of 2 C units to 16 C Fatty acidAddition of 2 C units to 16 C Fatty acid
 Do not require multi enzyme fatty acidDo not require multi enzyme fatty acid
synthase complexsynthase complex
 Group of enzyme ELONGASE is requiredGroup of enzyme ELONGASE is required
 Reaction occur in: ER, Microsome andReaction occur in: ER, Microsome and
MitochondriaMitochondria

3. Microsomal Elongation of Fatty Acids
 Predominant mechanism for chain elongation
 Malonyl Co A --- donor of 2C
 Addition takes place on COOH terminal of FA
 Reactions are similar as synthesis in cytosol

4. Reactions for elongation
of FA
Microsomal fractionPalmitoyl COA
B- Keto acyl COA
B- OH acyl COA
Enoyl COA
Stearyl COA
Condensation
Reduction
Dehydrase
Reduction
Malonyl COA
CO2
NADPH
NADP
NADPH
NAD
P
H2O
C16
C2
C16 + 2
C18

5. Reactions for Mitochondial elongation
of FA
Acyl COA
B- Keto acyl COA
B- OH acyl COA
β Unsaturated acyl COA
Acyl COA
Condensation
Reduction
Dehydrase
Reduction
Acetyl COA
COA.SH
NADPH
NADP
NADPH
NADP
H2O
C16
C2
C16 + 2
C18
Rare
In matrix
Acetyl
CoA
2C donor
Reverse
of β
Oxidation

6. Synthesis of
Unsaturated Fatty acids

7. Synthesis of unsaturated FA
 Reaction for addition of unsaturation or
double bond in the existing fatty acid
chain with or without elongation
 Site :
Liver plays major role
 Requirements:
Acyl desaturase enzymes,
NADPH / NADH;
O2 and Oxygenase enzyme

8. Synthesis of unsaturated FA
 Enzymes: Acyl desaturase present
in Microsome
 Acyl desaturase is
Non heme iron containing
enzyme
Have broad specificity
Four different types
Add CIS double bond at C9

9. Steps of unsaturated FA synthesis
Mono unsaturated fatty acid Poly unsaturated fatty acid
Stearyl CoA
Oleyl CoA
O2 + NADPH
+ H+
2H2O +
NADP+
Microsomal desaturase
C 18:0
C 18:1 Δ9
Linoleyl CoAC 18:2 Δ9,12
Linolenoyl CoAC 18:3 Δ6,9,12
Δ6 desaturase
O2 + NADPH + H+
NADP+ + 2H2O
Ecosa trienoic acidC 20:3 Δ8,11,14
Elongation in
ER
Malonyl CoA
Arachidonyl CoA
C 20:4 Δ5,8,11,14
O2 + NADPH + H+
NADP+ + 2H2O
Δ5 desaturase

10. Storage
Lipogenesis
and
Utilization
Lipolysis
LIPIDS

11. TAG DAG MAG
FFA
GLYCEROL
LYPOGENESIS
Epinephrine
Glucagon Insulin
FFAFFA
Increases cAMP Decreases cAMP
Lipolgenesis : synthesis of TAG
from FFA and Glycerol
Acetyl CoA
Carboxylase 
CitrateLong chain
fatty acyl CoA
 

12. TA
G
DAG MAG
FFA
GLYCEROLLYPOLYSIS
HORMONE SENSITIVE
TRIGLYCERYL LIPASE
Epinephrine
Nor-epinephrine
Glucagon
Thyroxine
ACTH
Insulin
Niacin
Prostaglandins
FFAFFA
Increases cAMP Decreases cAMP
Lipolysis : degradation of TAG to FFA and
Glycerol


13. Synthesis of
Glycerophospholipids
COMPOUND LIPIDS

14. Biosynthesis of glycerophospholipid -1
Phosphatidic acid
Glycerol
Glycerol
Glucose
DHAP
Glycolysis
Glycerol –3-P
ATP ADP NADPHNADP+
Acetyl COA
COA.SH
Glycerol kinase Glycerol-3-P DH
Acyl transferase
1, acyl Glycerol –3-P
Acetyl COA
COA.SH
Acyl transferase
1,2, di acyl Glycerol –3-P
Phosphatidic acid
From Adipose tissue
in LIVER
in LIVER &
ADIPOSE
CO2
H2O

15. Biosynthesis of glycerophospholipid-2
H2O
Pi
1,2, di acyl Glycerol –3-P
Phosphatidic acid
Phosphatidate phosphatase
1,2, di acyl Glycerol
Acetyl COA
COA.SH
Acyl transferase
Tri acyl Glycerol
Choline
Phospho Choline
Phosphatidyl Choline
Lecithine
CPD -- Choline
ATP
ADP
Choline kinase
CTP
PPi
CMP
Phosphatidyl choline DAG transferase
Phosphocholine
cytidyl transferase

16. Biosynthesis of glycerophospholipid-3
H2O
Pi
1,2, di acyl Glycerol –3-P
Phosphatidic acid
Phosphatidate hydrolase
1,2, di acyl Glycerol
CO2
Phosphatidyl
ethanolamine
Phosphatidyl
Serine
CPD --DAG
CTP
Pi
CMP
Phosphatidyl serine
transferase
DAG-cytidyl
transferase
Serine
Phosphatidyl serine
decarboxylase
3 SAM
S adenosyl
homocystine
N mehtyl
transferase
Phosphatidyl Choline
Lecithine