Upload
others
View
26
Download
0
Embed Size (px)
Citation preview
Digestion and Transport of
TAG by Plasma Lipoproteins
Chapter 18
Chapter 15
Lippincott’s Illustrated Review
Biochemistry
G
L
Y
C
E
R
O
L
FATTY ACID
FATTY ACID
FATTY ACID
TRIACYLGLYCEROL
G
L
Y
C
E
R
O
L
FATTY ACID
FATTY ACID
PHOSPHOACYLGLYCEROL
PHOSPHATE
ALCOHOL
Lipoproteins
• Multimolecular Complexes of Lipids
and Proteins
• For Transport of Lipids in the Plasma
• Lipids Include
– TAG Triacylglycerol
– CE Cholesterol Ester
– CH Cholesterol
– PL Phospholipids
Apolipoproteins
• The Protein Part of Lipoproteins
• Amphipathic
• Include Several Classes
Apo A, Apo B-48, Apo E.…
• Structural Role, Regulatory Role and
Binding to Cell Surface Receptors
Classes of LipoproteinsLipoprotein Density Protein Major Lipid
Chylomicrons
Composition
of Plasma
Lipoprotein
Lipoprotein Apo Protein Types
Chylomicrons Apo B, Apo C, Apo E
Dietary Lipids
VLDL Apo B, Apo C, Apo E
Endogenous TAG
IDL Apo B, Apo E
LDL Apo B Cholesterol
HDL Apo A, Apo C, Apo E
Cholesterol
Return to Liver
Digestion of Dietary Lipids
TAG + 2H2O 2 FA + MAG
CE + H2O FA + Cholesterol
Solubility Problem
Lipase
Colipase
MAG
FA
TAG
TAG
Cholesterol
Ester
,
Phospholipids
,
,
TAG
,
Fatty Acid
Monoacylglycerol
Cholesterol
Digestion of TAG with Short or
Medium Chain Fatty Acids
• Bigins in the Stomach
Lingual Lipase
Gastric Lipase
• Acid Stable
• Significance
– In Neonates
– In Pancreatic Insufficiency
Metabolism of SphingolipidsSphingophospholipids
Glycosphingolipids
Faisal Khatib MD; PhD
Faculty of Medicine, University
of Jordan
Sphingosine; Amino Alchol
Sphingosine; Amino Alchol
HO-CH-CH=CH-(CH2)12CH3
CH-NH2I
CH2-OH
Ceramide: Fatty Acid joined to
Sphingosine
HO-CH-CH=CH-(CH2)12CH3O║
CH-NH-C-(CH2)n-CH3ICH2-OH
2
Sphingomyelin is Phosphocholine
Ester of Ceramide
HO-CH-CH=CH-(CH2)12CH3O║
CH-NH-C-(CH2)n-CH3ICH2-O -CH2-CH2-N(CH3)3
+P
G
L
Y
C
E
R
O
L
FATTY ACID
FATTY ACID
PHOSPHOACYLGLYCEROL
PHOSPHATE
ALCOHOL
Sphingophospholipids
+ CO
Transfer Of Phosphocholine to Ceramide
Produces
Ceramide Phosphatidyl Choline
SphingomyleinDiacyl Glycerol
Sphingomylein
Glycolipids are Formed by Linking
one or More Sugars to Ceramide
Ceramide +
-Glucose or Galactose => Cerebroside
-Sulfated Galactose => Sulfoglycosphingolipids
-Oligosaccharide => Globoside
-Oligosaccharide with NANA => Gangliosides
N-Acetylneuraminic Acid (NANA)
Activated Donors in Glycolipids
Synthesis
• UDP-Glucose
• UDP-Galactose
• UDP-N-Acetylgalctoseamine
• CMP- N-Acetylneuraminic Acid
Galactocerbroside
Glucocerbroside
Transfer of Sulfate Group to Galactocerbroside Produces
Sulfogalatocerbroside (Sulfatide)
Degradation of Sphingolipids• Hydrolytic Enzymes, Specific for the Sugar
• - α Galactosidase
- β Galactosidase
- neuraminidase
- Hexoaminidase
• In Lysosomes
• Enzymes are firmly Bound to Lysosomal Membrane.
• The pH Optimum 3.5-5.5
• Stepwise Sequential Process
• “Last on, First off”
Glc Gal
Gal
GalNAcGal
NAcGal
NANA
NANA
NANA
Glc
Glc Gal
Glc Gal
βGalactosidase
βHexoseaminidase
neuraminidase
Sphingolipidoses
• Lipid Storage Diseases
• Defect in one of the Enzyme
• Accumalation of Specific Lipid
Substrate of the Defective Enzyme
Inherited as Autosomal RecessiveDisease
• Brain is Mostly Affected.
• Extent of Enzyme deficiency is the same in
Different Tissues.
Degradation of Sphingomyelin
Sphingomyelin
Ceramide
SphingosineSphingomyelinase
Ceramidase