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Oral biology > OB S - Salivary pellicle 1 > Flashcards

OB S - Salivary pellicle 1 Flashcards

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1
Q

Name some salvia components.

A
  • histatins
  • lysozyme
  • proline-rich proteins
  • amylases
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2
Q

How can protein shape change?

A

according to conditions

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3
Q

what are the 2 functions of proteolytic cleavage?

A

1 function as a long molecule but can have another function as a peptide

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4
Q

what does localisation determine ?

A

what happens i.e can be localised to an area that favours its role

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5
Q

Name some salivary functions.

A
  • Antibacterial i.e amylases/mucins
  • Anti-viral i.e cystitis
  • Anti-fungal i.e histatins
  • Buffering -carbonic anhydrases
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6
Q

what is understanding natural processes linked to?

A

therapeutic innovations

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7
Q

Describe the formation of a pellicle.

A

Material deposited rapidly on freshly cleaned tooth:

  • Forms in minutes
  • 20 mins tooth surface covered
  • 120 mins 1-10 μms thick
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8
Q

what does the pellicle contain?

A

Peptides, proteins, enzymes, glycoproteins, lipids and glycolipids:

  • -ve charged enamel surface
  • -ve charged salivary proteins
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9
Q

what does the composition and structure of the pellicle vary with?

A

time and local microenvironment

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10
Q

What is the pellicle?

A

0.1 - 1.0 μm thick layer of macromolecular material on the mineral surface of teeth
– cell-free proteinaceous layer
– forms rapidly on cleaned tooth surfaces

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11
Q

what are the 3 functions of the pellicle?

A

• Selective adsorption of hydroxyapatite-reactive salivary
proteins, serum proteins and microbial products – contains most salivary proteins and lipids
• Diffusion barrier
– protects against bacterial acids
– slows loss of dissolved calcium and phosphate ions
• Renewable lubricant, helps protect teeth from attrition and abrasion

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12
Q

what ions does the enamel surface contain?

A

cations (Ca++) & anions (OH-) (PO4- -)

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13
Q

what is the net charge of the enamel surface?

A

net -ve charge

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14
Q

what does contact with salvia do to the pellicle?

A

produces a charged layer :

  • hydration layer or stern layer
  • counter ions 90% Ca++
  • remains while animal is in contact with liquid
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15
Q

what is at high concentration at the tooth surface?

A

F-

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16
Q

where does pellicle formation occur?

A

HA discs -dics of hydroxyapatite so the charge varies across the surface

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17
Q

what gives protection of the tooth?

A

calcium phosphate

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18
Q

what is an impure form of calcium HA?

A

tooth mineral

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19
Q

what does mass action of calcium phosphate govern?

A

dissociation

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20
Q

what does loss of calcium phosphate depend on ?

A

amount of Ca, PO4 & 2OH in

solution

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21
Q

what happens in low pH?

A

supersaturation decreases

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22
Q

what happens at critical pH?

A

salvia no longer supersaturated

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23
Q

what happens in high pH (alkaline)?

A

calcium phosphate can precipitate

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24
Q

what does precipitation require?

A

nucleation sites

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25
Q

what does the pellicle mask?

A

the underlying HA crystals from acting as nucleation sites

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26
Q

what can act as a nucleation site?

A

plaque

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27
Q

Discuss pH:salivary bicarbonate.

A
  • Salivary bicarbonate (HCO3-) stabilised by gaseous CO2
  • HCO3- most unstable (high) near salivary ducts
  • May result in higher pH can result near duct openings making Calcium Phosphate more likely to precipitate
28
Q

what is the key function of bicarbonate?

A

mop up protons and protects the tooth

29
Q

what is unique to salvia?

A

carbonic anhydrase IV

30
Q

what does carbonic anhydrase IV do?

A

Drives the process pf bicarbonate binding to protons and turning them into water

31
Q

How does carbonic anhydrase IV act as phase buffering?

A

– Phase conversion of dissolved CO2 into a volatile gas

– Contributes to neutralising acid

32
Q

Describe carbonic anhydrase IV.

A

– Secreted from aciner cells as isoenzyme
– No direct role in buffering saliva
– DMTF index links its concentration to caries
– Binds to pellicle
– Localised protection through removal of H+

33
Q

what has an affinity for apatitic surfaces suggests it binds before the pellicle formation?

A

Statherin

34
Q

what does statherin prevent?

A

both primary and secondary calcium phosphate disposition

35
Q

What is statherin and what does it occupy?

A

• Acidicphosphoprotein
– N-terminal basic residues
– NMR helical structure
– mimics periodicity of acid phosphate clusters on HAp

• Occupies sites that would otherwise be used for nucleating crystallisation?

36
Q

what does PRPs stand for?

A

proline-rich proteins

37
Q

Describe proline-rich proteins.

A 
•  Family of proteins
–  70% of total salivary protein
•  Rich in Proline (25-40%), Glutamic acid glutamine & glycine
•  Amphiphilic
–  80% hydrophobic 
–  20% hydrophilic
•  3 groups
–  acidic (16 kD)
–  basic (6-9 kD)
–  glycosylated (36 kD)
38
Q

what characteristic can proline give a molecule?

A

flexibility

39
Q

Describe proteolytic cleavage.

A

– Oral fluid & glandular
secretions are distinct
– Sterile to non-sterile
– Exposure to bacteria derived proteases.
– Release of peptides derived (in particular) from Acidic & Basic PRPs, Statherin & Histatins.

40
Q

Describe proline-rich proteins binding to the pellicle.

A

• Early binding to pellicle, and incorporated into mature
biofilms.
• N-terminus shows structural similarity to Statherin.
• First 30 amino acids negatively charged.
• Proposed to occupy sites where Calcium phosphate deposition would occur

41
Q

What else can PRPs interact with?

A

Calcium & phosphate ions away from the HA surface where they may act as ‘sink’ & limit growth of these complexes. Conformational changes may release Calcium & Phosphate ions when required

42
Q

what are 2 strong inhibitors of calcium phosphate?

A

– Stratherin

– Acidic Proline-rich proteins

43
Q

what are 2 moderate inhibitors of calcium phosphate?

A

– Histatins

– Cystatins

44
Q

what are 2 weak inhibitors of calcium phosphate?

A

– Mucins

– Amylase

45
Q

How is early caries repaired despite presence of mineralization inhibitors in saliva?

A
  • Surface layer of early carious lesion forms impermeable barrier to diffusion of high mol.wt. inhibitors.
  • Still permeable to calcium and phosphate ions
  • Inhibitors may encourage mineralization by preventing crystal growth on the surface of lesion by keeping pores open
  • Inhibitors could form complexes from which Ca2+ & PO4- can be released
46
Q

what is the most abundant salivary enzyme?

A

Alpha-amylase

47
Q

what does alpha -amylase do?

A

Hydrolyzes α(1-4) glycosidic bonds of polysaccharides;
– Insoluble (large) Starch broken down to soluble starches
– Clears carbohydrate debris on the tooth

48
Q

what is the major end product of alpha amylase?

A

maltose

49
Q

what is alpha amylase resistant to?

A

proteolytic cleavage

50
Q

what happens to alpha amylase on the pellicle?

A

Immobilised on pellicle, in association with mucin &/or antibodies

51
Q

what does von ebner’s glands of tongue secrete?

A

lingual lipase

52
Q

what is lingual lipase involved in?

A

• Involved in first phase of fat digestion

– i.e. dietary lipids

53
Q

what does lingual lipase hydrolyse?

A

Hydrolyzes medium- to long-chain triglycerides

– Diglycerides & free fatty acid are the primary products

54
Q

what constitutes 90% of acquired pellicle?

A

salivary glycoproteins :

26% of salivary proteins

55
Q

what does salivary glycoproteins contain?

A

acidic sugars (-ve) e.g sialic acid

56
Q

what are mucin functions?

A

Tissue Coating
– Protective coating about hard and soft tissues
– Primary role in formation of acquired pellicle

Lubrication
– Align themselves with direction of flow
• (characteristic of asymmetric molecules)
– Increases lubricating qualities
• Film strength determines how effectively opposed moving surfaces are kept apart

57
Q

what are the two forms of salivary mucins?

A
  • oligomeric mucin glycoprotein (MG1)

- Monomeric mucin glycoprotein (MG2)

58
Q

Describe oligomeric mucin glycoprotein (MG1).

A

– Mixture of two mucins (MUC5B & MUC4) >1 x 106 kDa
– Gel-forming mucin (MUC5B) & membrane-bound (MUC4)
– Disulfide linked multimers
– Mucosal & enamel surface coating (major role)

59
Q

Describe monomeric mucin glycoprotein (MG2).

A

– One gene product (MUC7) 200-250 kDa
– 170 O & N-linked side chains 68%
– Influence on oral microbiota (major role)

60
Q

what is the estimated hydrogen peroxide levels in whole salvia?

A

8-14 uM

61
Q

what is hydrogen peroxide a major source for?

A

Facultative anaerobes major source

– e.g. S. sanguinis & S. mitis

62
Q

what is hydrogen peroxide converted to in mammalian cels?

A

hydroxyl radicals

-damage DNA and lipids

63
Q

what is dismutation of hydrogen peroxide critical for?

A

Protecting mucosa fibroblasts etc:

  • bacterial catalases
  • salivary peroxidases
64
Q

Describe salivary peroxidase.

A

• Sialoperoxidase (hSPO, salivary peroxidase)
– 78 kD
– secreted by the parotid and submandibular glands
– Readily adsorbed to various surfaces of mouth: enamel, salivary sediment, bacteria, dental plaque

65
Q

what do salivary peroxidase do?

A

– Oxidise mainly salivary SCN- in the presence of H2O2

– Protect host from H2O2 toxicity

66
Q

Describe thiocyanate (SCN-).

A

– Electron donor in reaction
– normal component of saliva
– salivary concentration depends on diet and smoking habits

67
Q

Thiocyanate reactions .

A

look at slide

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