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MONTANO, Elisa B.
MONTANO, Ma. Sheena-Day D.
MORALES, Reina Lyria C.
MORZO, Dan Israel B.
MUKSAN, Ufyla Nashrene M.
NAPA, Christa Rosemary Faith D.M.
LEARNING OBJECTIVES:
Define what are glycosaminoglycans and proteoglycans and their biologic importance.
Know the different mucopolysaccharidoses, identify the deficient enzyme in each type and its clinical characteristics.
Know the role of glycosaminoglycans in cancer, atherosclerosis and arthritis.
Glycosaminoglycans (GAGs)
Long, unbranched heteropolysaccharide chains
Repeating Disaccharide UnitsAmino Sugar
D-GlucosamineD-Galactosamine
Acidic Sugar (Uronic Acid)D-Glucuronic AcidL-Iduronic Acid
All GAGs, except Hyaluronic Acid, contains Sulfur in atleast one of its sugars
Essential components of the ECM
Disaccharide Units
A. Amino Sugars May either be:
1. D-Glucosamine2. D-Galactosamine
Contains an Aminogroup (-NH2)
Usually acetylated May be Sulfated on
C4, C6, or on a nonacetylated Nitrogen
Disaccharide Units
B. Acidic Sugars May either be:
1. D-Glucuronic Acid2. L-Iduronic Acid
C5 epimer Contain carboxyl
group (-COOH)
Negative at physiologic pH
May contain Sulfur
Exception:Keratan Sulfate
Galactose in place of Acidic Sugar
Major GAGs
CHONDROITIN SULFATE
DERMATAN SULFATE
KERATAN SULFATE HEPARIN HEPARAN
SULFATE HYALURONIC ACID
Chondroitin Sulfate
Most abundant GAG in the body Disaccharides:
Acidic Sugar: Glucuronic Acid (GlcUA) Amino Sugar: N-Acetylgalactosamine (GalNAC)
C4 – Chondroitin 4-Sulfate C6 – Chondroitin 6-Sulfate
Function: Form proteoglycan aggregates with Keratan Sulfate In Cartilage, bind Collagen and hold fibers in a tight, strong
network Localization:
Cartilage Tendons Ligaments Bone Aorta
Dermatan Sulfate
Disaccharides: Acidic Sugar: L-Iduronic Acid (IdUA) Amino Sugar: N-Acetylgalactosamine
(GalNAC) Localization:
Skin Blood Vessels Heart Valves
Keratan Sulfate
Most Heterogeneous GAG Sulfate content is variable Disaccharides:
Acidic Sugar: Galactose (Gal) Amino Sugar: N-Acetylglucosamine
(GlcNAC) Function:
Form proteoglycan aggregates with Chondroitin Sulfate.
Localization: Cartilage Cornea
Heparin
Only intracellular GAG Almost all Glucosamine residues are Sulfated Disaccharides:
Acidic Sugar: Glucuronic Acid (GlcUA) or Iduronic Acid (IdUA)
Amino Sugar: Glucosamine (GlcN) Function:
Anticoagulant Localization:
Mast Cells that line arteries Liver Lungs Skin
Heparan Sulfate
Difference from Heparin: Extracellular Some Glucosamines are acetylated Fewer Sulfate Groups
Disaccharides: Acidic Sugar: Glucuronic Acid (GlcUA) or
Iduronic Acid (IdUA) Amino Sugar: Glucosamine (GlcN)
Localization: Basement Membranes Cell Surfaces Skin Fibroblasts Aortic Wall
Hyaluronic Acid
Difference from other GAGs: Unsulfated Not covalently attached to protein Only GAG not limited to animal tissue, also found in
bacteria. Disaccharides:
Acidic Sugar: Glucuronic Acid (GlcUA) Amino Sugar: N-Acetylglucosamine (GlcNAC)
Function: Lubricant Shock Absorber
Localization: Synovial fluid of joints Vitreous humor of the eye Umbilical cord Lose Connective Tissue
Proteoglycans
Core Proteins containing covalently linked GAG chains
Major components of Ground Substance CHON-CHO Ratio
Protein : around 5% Carbohydrates : up to about 95% of its weight
All GAGs, except for Hyaluronic Acid, are found covalently attached to proteins, forming proteoglycan monomers.
Proteoglycans
Proteoglycans
Aggrecan Major type of proteoglycan in cartilage Very large proteoglycan Bottle brush structure Components:
Core Protein Keratan Sulfate Chondroitin Sulfate Link Proteins Hyaluronic Acid
Mucopolysaccharidoses
Mucopolysaccharidoses is a collection of metabolic disorders that arise when mucopolysaccharides are unable to break down, causing a fault in the production of a particular gene. This results from abnormalities of specific enzymes.
Types of Mucopolysaccharidoses Hurler Scheie Hurler- Scheie Hunter Sanfilippo A/B/C/D Morquio A/B Maroteaux-Lamy Sly
Hurler’s syndrome/ Mucopolysaccharidosis type I (MPS I - H)
Enzyme defect: α-L-iduronidase Affected GAG: dermatan sulfate, heparan sulfate s/s:
Corneal clouding Abnormal bones in the spine Claw hand Halted growth / dwarfism Heart valve disease Joint stiffness Mental retardation Thick, coarse facial features with low nasal bridge Early mortalityIt is the most severe of the MPS I subtypes.
Scheie (MPS I – S)
Enzyme defect :α-L-iduronidase Affected GAG: dermatan sulfate, heparan sulfate s/s:
corneal clouding broad mouth with full lips hirsutism prognathism joint stiffening
Children born with this form normal intelligence and may live to adulthood.
Hurler-Scheie (MPS I-HS)
Enzyme defect: α-L-iduronidase Affected GAG: dermatan sulfate, heparan
sulfate s/s:
Dwarfism Progressive blindness Deafness Heart failure Normal/ near normal intelligence
Hunter’s Syndrome (MPS II)
Enzyme defect: L-iduronate-2-sulfatase Affected GAG: dermatan sulfate, heparan
sulfate s/s:
mild and severe forms only X-linked MPS (usually seen in males) slowly progressive valvular disease organomegaly facial and physical deformities no corneal clouding mental retardation death before 15 yrs except in mild form then
survival to 20 - 60 yrs
Sanfilippo (MPS III)
Sanfilippo A Enzyme defect: heparan N-sulfatase Affected GAG: heparan sulfate s/s marked with severe neurological symptoms profound mental deterioration coarse facial features walking problems fairly normal height skin, brain, lungs and skeletal muscle are affected in all
4 types of MPS-III
Sanfilippo
Sanfilippo B Enzyme defect: α-N-acetyl-D-
glucosaminidase affected GAG: heparan sulfate s/s:
phenotype similar to III A
Sanfilippo
Sanfilippo C enzyme defect: acetylCoA:α-
glucosaminide-acetyltransferase affected GAG: heparan sulfate s/s:
phenotype similar to III A
Sanfilippo
Sanfilippo D enzyme defect: N-acetylglucosamine-6-
sulfatase Affected GAG: heparan sulfate s/s:
phenotype similar to III A
Morquio
Morquio A Enzyme defect: galactose-6-sulfatase Affected GAG: keratan sulfate, chondroitin 6-sulfate s/s:
corneal clouding, odontoid hypoplasia, aortic valve disease, distinctive skeletal abnormalities – short stature, short
trunk widely spaced teeth large head intelligence is normal unless hydrocephalus develops and
not treated
Morquio
Morquio B Enzyme defect: β-galactosidase Affected GAG : keratan sulfate s/s:
severity of disease similar to IV A
Maroteaux-Lamy (MPS VI)
Enzyme defect: arylsulfatase B also called N-acetylgalactosamine-4-sulfatase
Affected GAG: dermatan sulfate s/s:
aortic valve disease shortened trunk, crouched stance, and
restricted joint movement by age 10 normal intelligence corneal clouding coarse facial features
Sly Syndrome (MPS VII)
Enzyme defect: β-glucuronidase Affected GAG: heparan sulfate,
dermatan sulfate, chondroitin 4-, 6-sulfates
s/s: hepatosplenomegaly dystosis multiplex wide spectrum of severity hydrops fetalis
Type:Syndrome Enzyme Defect Affected GAG Symptoms
HurlerMPSIH (MPS1H)
α-L-iduronidasedermatan sulfate, heparan sulfate
corneal clouding, dystosis multiplex,
organomegaly, heart disease, dwarfism, mental retardation;
early mortality
ScheieMPSIS (MPS1S)
α-L-iduronidasedermatan sulfate, heparan sulfate
corneal clouding; aortic valve disease; joint stiffening; normal
intelligence and life span
Hurler-ScheieMPSIHS (MPS1HS)
α-L-iduronidasedermatan sulfate, heparan sulfate
intermediate between I H and I S
HunterMPSII (MPS2)
L-iduronate-2-sulfatasedermatan sulfate, heparan sulfate
mild and severe forms, only X-linked MPS, dystosis multiplex,
organomegaly, facial and physical
deformities, no corneal clouding, mental
retardation, death before 15 except in mild form then survival to 20
- 60
MPS VIII, a designation no longer used
GENETICS
Mucopolysaccharidoses are autosomal recessive disorders, meaning that only individuals inheriting the defective gene from both parents are affected.
TREATMENT:
Currently there is no cure for these disease syndromes. Medical care is directed at treating symptomatic conditions and improving the person's quality of life.
Enzyme replacement therapy has proven useful in reducing non-neurological symptoms and pain
CANCERATERHOSCLEROSISARTHRITIS
Roles of Glycosaminoglycans in
Cancer
Glycosaminoglycans and proteoglycans both play major roles in multiple cancer-related processes.
Changes in expression of these molecules, as well as of enzymes involved in their biosynthesis and degradation, contribute to the different steps of tumor progression.
Atherosclerosis
The intima of the arterial wall contains hyaluronic acid, chondroitin sulfate, dermatan sulfate and heparan sulfate proteoglycans.
Dermatan sulfate appears to be the major GAG synthesized by arterial smooth muscle cells.
Dermatan sulfate may play an important role in the development of the atherosclerotic plaque.
ARTHRITIS
Proteoglycans may act as autoantigens
Amount of chondroitin sulfate diminishes with age
Whereas the amount of keratan sulfate and hyaluronic acid increases.
Increased in the activity of aggrecanase which acts to degrade aggrecan
References
Berg, Jeremy M. et al: Biochemistry, 6th Edition. New York: W.H. Freeman and Company, 2007. 312-313.
Champe PC, Harvey RA: Biochemistry, 2nd Edition. Philadelphia: Lippincott, 1994. 147-155.
http://www.ncbi.nlm.nih.gov/pubmedhealth http://themedicalbiochemistrypage.org Harper’s Illustrated Biochemistry 27th and 28th Edition Lippincott Illustrated Reviews Biochemistry 4th Edition Murray, Robert K. et al: Harper’s Illustrated
Biochemistry, 27th Edition. McGraw-Hill Medical, 2006. 118-119, 551-564.
Principles of Biochemistry By Lehninger
References:
Sasisekharan, et al. 2002. Role of heparan-sulphate glycosaminoglycans in tumour metastasis. Roles of heparan-sulphate glycosaminoglycans in cancer, Nature Reviews Cancer 2, 521-528.
Swanson, Todd A. et al: Biochemistry and Molecular Biology, 4th Edition. Philadelphia: Lipincott Williams & Wilkins, 2007. 8, 10, 174.
THANK YOU! =)