Periodontal Ligament Biochemistry Flashcards
What cells are in the periodontal ligament
Fibroblasts
Cementoblasts
Osteoblasts
What fibres and other things make up the periodontal ligament
Nerves and vasculature
Extracellular matrix
Fibres (major is collagen the minor is oxytalan and elastin)
Ground substance
How does elastin for and mature?
Oxytalan
Elaunin
Elastin
Elastin protein is deposited in these oxytalan fibres until the mature into elastin
This makes it resemble foetal connective tissue
What is elastin made of
10-15 no microfibrils if oxytalan fibre
Microfibrillat component 10%
Amorphous polymeric fore (90%) elastin protein
What is collagen made of (structure)
All made of 3 collagen polypeptide (alpha polypeptides)
What is the structure of each polypeptide collagen chain
Tripeptide glycine followed by 2 amino acids proline or its hydroxylated form. The third amino acid is alanine
If we looked down the chain we could see the single H side chain faces the middle because there is no steric hinderance here
Every third amino acid proline has its bulky side chain orientated outward this side chain forms H bonds with other things around in the surrounding solution
What collagen types form the PDL
Type 1 80%
Type 3 20%
What is the importance of hydroxyproline in the collagen structure
Stability in the triple helix through OH group
What happens when hydroxilation of proline is absent
Scurvy a connective tissue disease
How is proline converted to hydroxyproline
Proline is hydroxilated via a vitamin C dependant enzyme prolyl hydroxalysae. Vitamin C is a reducing agent keeping fe2+ ions mood
How is collagen formed (chains assemble)
Alpha chains assemble and are stabilised by S-S bonds at the carboxyl end of the chains then the helix forms spontaneously and the globular end at the N terminus forms
What happens to the procollagen when it leaves the cell to the extracellular matrix
The globular ends are cleaved leaving the tropocollagen that can now assemble into fibres
What happens in fibrillogenesis
This is the aggregation of tropocollagen to form fibrils intermolecular cross links form
How are the fibrils stabilised
Covalent cross links from modified lysine and hydroxylysine residues
Lysyl oxadase converts r groups of LYS and HYL to aldehydes
They are all reducible
What are intramolecular allysine cross links
These are formed within the actual tropocollagen molecules
What happens to cross linked as collagen ages.
Is this the same in the PDL
More stable non reducible cross links form spontaneously
There are no non reducible cross links in the PDL
What is the ration of DHLNL:HLN
1:3
Giver and overview of collagen synthesis
Synthesis of alpha chains Hydroxylation of PRO&LYS Glycosylation og HYL and ASN Alignment of pro a chains Pro-collagen triple helix
Outside -
Cleavage if terminal ends
Aggregation stagger array
Formation of intermolecular cross links
What is the hierarchical structure of collagen type 1
Procollagen Tropocollagen Microfibrils Fibrils Fibres Fibre bundles
How is collagen broken down
Collagenase enzyme (matrix metalloprotiase) produced as an inactive precursor it cleaves collagen to 3/4 and 1/4 parts In the PDL phagocytosis by fibroblasts is an significant degradation factor
What is the collagen synthesis in the PDL and degradation compared to everything else
6 times alveolar bone and 4 times skin
Degradation is 15 times what it is in the skin and 6 times what it is in alveolar bone
Approx 40 min cycle in PDL
What happens to gelatinise activity in sheep with diseased mouths
Greater activity more degradation
What does the Western blot of GCF show
Collagen only present in GCF in diseased sheep
What comprises ground substance
Non collagenous proteins
Hyaluronic acid
Proteoglycans
Glycoproteins such as fibronectin and these are protiase resistant
