OB S- pellicle 2 Flashcards
what is the enamel pellicle?
the layer of material acquired by a cleaned tooth
what is included in the enamel pellicle?
– Mucins – Acidic Proline-rich proteins – Statherin – Amylase – Lysozyme
what are mucin functions?
- forming buffer between 2 surfaces
- allowing movement of materials across and providing protection
- tissue coating (aggregate microbes for removal and concentrates anti-microbial molecules at mucosal interface)
- lubrication
Describe the bacterial interactions of MG1 .
– Attracts some species S. sanguinis, S. mitis & Actinomyces spp.
– Associated with soluble phase, and rapid flushing out of material
Describe the bacterial interactions of MG2.
– Attracts many bacterial species;
• S. sanguinis, S. gordonii, E. corrodens, S. aureus, P. aeruginosa
– Long protein core with short CHO chains that often end in sialic acid
• S. sanguinis, S. mitis (sialic acid adhesins)
– Neuraminidase cleaves sialic acid exposing galactose
– Galactose binding bacteria
(sides chains can be modified , can take carbohydrates which can be used as binding sites for certain bacteria (reveal sites)
Describe the proteolytic cleavage of MG2.
-peptides assessed in vitro kill bacteria (streptococci, P. gingivalis)
- potent anti fungal peptides characterised (kill azole & amphotericin B resistant Candida & Crytpotoccus sp.
, Crosses fungal membrane and accumulates within the cell, Effective in animal models of Candidiasis)
Cleavage that goes on can release antimicrobial properties
what does proteolytic cleavage cause a release of?
Release of peptides derived (in particular) from Acidic & Basic PRPs, Statherin & Histatins
Describe acidic (16kD) PRPs.
– unique to saliva – affinity for hydroxyapatite – newly formed pellicle – important for Ca2+ & PO4- levels – degradation products (peptides) have antibacterial activity -Conformational change - C-terminus exposed as receptor
Describe basic (6-9kD) PRPs.
– found in saliva & nasal/ bronchial secretions
– complex with tannin & tannic acid
Describe glycosylated (36kD) PRPs.
-newly formed pellicle
– bind to hydroxyapatite
– binds S. mutans efficiently
what do salivary proteins appear to be involved in?
Preventing or promoting bacterial adhesion to oral soft and hard tissues
What are PRPs strong promoters of?
bacterial adhesion:
- Amino terminal :control calcium phosphate chemistry
- Carboxy terminal :interaction with oral bacteria
Describe how interactions of oral bacteria with PRPs and other pellicle proteins is highly specific.
– Depends on proline-glutamine carboxy-terminal dipeptide
• e.g. P. gingivalis preference for HA coated with PRPs
– PRPs in solution do not inhibit adhesion of bacteria
What does statherin prevent?
both primary and secondary calcium phosphate disposition
what does Statherin aid?
Aids A. viscosus & F. nucleatum binding to HAp
What is the C-terminal of statherin involved in?
only upon binding to pellicle & conformational change
What are the functions of alpha- amylase?
• α-amylase – α 1-4 glycosidic bonds • Digestivefunction – e.g. starch, amylose • Essential component of salivary pellicle • Bacterial Receptor – S. sanguinis, S. gordonii • Forms heterotypic mixed micelle like structures
what are glucans?
glucose polysaccharides with glucose molecules joined by 1,3-α- or 1,6-α- linkages
Name water-soluble glucans with 1,6-α- links.
dextrans
Name water-insoluble glucans with 1,3-α- links and 1,6-α- links.
Mutans
Describe binding pellicle-attached glucosyltransferases .
- Such immobilized enzymes are still active and continue to produce sticky polysaccharide
- Bound GTFs also act as binding sites for bacterial adhesion
what immunoglobulins are found in the pellicle?
IgA and IgG
what immunoglobulin predominates?
IgA2 -shorter hinge resists proteases
what does pellicle -attached immunoglobulins inhibit?
Inhibits growth of some species & contributes to adherence of other species
what underpins the idea of immunising against S.mutans?
presence of antiseptic paint
Describe cystatins.
• Inhibitors of cysteine proteases (e.g. bacterial & viral)
• Include unique cystatins restricted to oral
environment
• Cystatin SA linked with pellicle formation & remineralisation
• May function in control of periodontal disease
• Protect other salivary proteins from degradation
(protective role -reducing microbial population)
Describe histatins.
• Histidine rich cationic (+ve ) peptides
– family of at least 12 (1,3&5major saliva forms)
• Incorporated into acquired pellicle
What 2 properties does histatins have?
- antifungal properties
- antibacterial properties
Describe the antifungal properties of histatins.
– Histatin 5 anti-candidal
• binds receptor, target mitochondria, inhibit respiration & leads to production of reactive O2 species
Describe the antibacterial properties of histatins.
– bactericidal against S.mutans
– Inhibits co-aggregation of P.gingivalis & S.mitis
-Disrupt in vitro biofilms produced by a number of oral bacteria
Name other components of the pellicle.
• Lysozyme
• Lactoferrin,
– (globular protein with antimicrobial/antifungal properties)
• albumin
• Other bacterial enzymes & products
where is lysozyme present?
present in numerous organs and most body fluids
where is oral lysozyme derived from?
at least 4 sources:
-major and minor salivary glands, phagocytic cells and gingival crevicular fluid (GCF)
Describe the actions of lysozyme.
• Cleaves β-1,4 linkage between N- acetylmuramic acid (NAM) & N- acetylglucosamine (NAG)
– Gram negative bacteria are generally more resistant due to outer LPS layer
• Activates bacterial autolysins - ‘suicide packages’
(attacking cell wall and causing its degredation)
What is lactoferrin?
• Iron chelating glycoprotein
– Single polypeptide, MW 80 kD
– Member of transferrin family of iro-binding antibacterial proteins
what does lactoferrin have a high affinity for?
Fe+3
what is the principal action of lactoferrin?
blocks growth of iron dependent organisms with bacteriostatic effect
what does lactoferrin do?
– N-terminal peptide product of pepsin (contains no Fe binding sites).
– Broad spectrum bactericidal, antiviral & antifungal
– Binds to LPS & inhibits endotoxin activity
Describe antimicrobial activity of HOSCN/OSCN-
• Product of Salivary Peroxidase activity
– Enzymes absorb onto Hydroxyapatite
• Against a variety of microorganisms
– e.g. S. mutans, lactobacilli, yeasts, even some viruses
• Can oxidize sulfhydryl groups of enzymes
• Block glucose uptake
• Inhibit amino acid transport
• Damage inner membrane, leading to leakage of cell
• Disrupt electrochemical gradients
• Inhibits hexokinase (essential for Glycolysis)
What are antimicrobial components of salvia?
• Lactoferrin • IgA • Mucins • Antimicrobial peptides • Enzymes – Lysozyme, glycosidases, peroxidase, esterase, transferase • Proteins – Glycoproteins – Statherins – Histidine-rich Proteins – Proline-rich Proteins
what binds carbohydrates and what does this allow?
Group of adhesins- called lectins , binding allows build up of bacteria, insoluble phae its good cause it collect bacteria for removal
Describe the stages of pellicle formation.
• Molecules attach immediately • 1-2 μMs thick before bacteria attach – 1 hour • Transition from pellicle to plaque – MG1, sIgA, lysozyme all bind to bacterial cell walls – Pioneer species – S. gordonii, S. sanguinis etc. • Rapid increase up to 2 hours • Slower growth until reaches 5-10 μMs
