SALIVA & SALIVARY PROTEINS

what is saliva

a secretion of proteins and glycoproteins in a buffered electrolyte solution

what are the functions of saliva (7)

• lubricant for:

  • mastication

  • swallowing

  • speech

• oral hygiene - washes away debris

• defensive function - has anti-bacterial/ viral/ fungal properties

• maintenance of oral pH - pH ≈ 7.2

  • bicarbonate/ carbonate buffer system for rapid acid neutralisation

• contains digestive enzymes

• a solvent necessary for taste

• remineralisation - contains Ca²⁺ and PO₄^3-

what is saliva dysfunction associated with (3)

• oral pain

• infections

• increased risk of dental caries

what is the average flow rate in ml/ min

0.3-7ml per minute (depends on activity)

what is the daily salivary secretion volume in adults from both major and minor salivary glands

800-1500ml from major and minor salivary glands

what does the pH of saliva range from

6.2-7.4

serous saliva VS mucous saliva

serous saliva

• mainly contains enzymes like alpha amylase for starch digestion

mucous saliva

• contains mucins for lubrication of mucosal surfaces

what type of salivary glands are the parotid, submandibular, sublingual and minor salivary glands

• parotid = serous

• submandibular = seromucous

• sublingual = seromucous but predominantly mucous

• minor salivary glands (> 600) = mainly mucous

what factors affect the composition and amount of saliva produced (8)

• flow rate

• circadian rhythm - we produce less saliva at nighttime

• type and size of gland

• duration and type of stimulus

• diet

• drugs

• age

• gender

what is mucositis and how is it classified

mucositis: the painful inflammation and ulceration of the mucosa lining the digestive tract i.e. mouth and GI tract (xerostomia can increase the risk of mucositis)

• classified by Grades 1-4

outline Grade 1 mucositis

• soreness

• ± erythema

• mild symptoms

• intervention not needed

outline Grade 2 mucositis

• erythema

• ulcers

• moderate pain

• patient can still swallow

outline Grade 3 mucositis

• considered severe mucositis

• extensive pain

• ulcers with extensive erythema

• patient cannot swallow food

outline Grade 4 mucositis

• considered severe mucositis

• life-threatening consequences

• alimentation is not possible

what is mucositis often caused by

chemotherapy/ radiotherapy

what type of salivary gland are Von Ebner’s

serous

outline the protein composition of saliva

proteomics and peptidomics used to analyse saliva

• 3652 protein detected

• 12,562 peptides detected

• 51% of proteins and 79% of peptides also contained in plasma proteins

  • proteins in saliva are similar to proteins in plasma just in smaller amounts

what proteins are found in saliva

• amylase

• mucin - MG1

• mucin - MG2

• histatin

• statherin

• proline rich protein (PRP)

• cystatin

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what are the main types of mucins and outline each

MG1

• 78% CHO

• 15% protein

• 7% sulphate

• O-glycosylated

• N- and C termini are rich in cysteine

MG2

• glycosylated

• contains threonine-rich tandem repeats

what characteristics do MG1 and MG2 share

• terminal sialic acid groups

• form complexes with other salivary molecules

• glycosylated

which salivary proteins are antimicrobial

• lysozyme

• sialoperoxidase/ lactoperoxidase

• lactoferrin

• histatins

• secretory IgA

• IgG

outline lysozyme

• also known as muramidase

• cleaves bacterial peptidoglycan - major component of Gram positive bacterial cell walls

outline sialoperoxidase/ lactoperoxidase

sialoperoxidase/ lactoperoxidase

• cleaves terminal sialic acid groups of bacteria

• peroxidase enzyme

• produce oxidised intermediates through catalysis of hydrogen peroxide

outline lactoferrin

• present in body secretions like breast milk and neutrophil granules

• binds to free iron ions (Fe3+) which bacteria use for nutrients - removes the substrate needed for bacterial growth

• binds to LPS of bacterial cell walls (major component of Gram negative bacteria outer membrane)

outline histatins

• unique to saliva

• very small proteins

• antifungal and antibacterial as well

• disrupt membrane function

• bind to LPS and other receptors causing formation of reactive oxygen species

• binds to tanins, mucins and enamel

what is the main immunoglobulin found in mucous secretions

• secretory IgA - antimicrobial

where is secretory IgA found

• tear glands

• salivary glands

• mammary glands

• respiratory system

• GU tract

• GI tract

what is secretory IgA produced by

B-lymphocytes adjacent to mucosal cells

what is the structure of secretory IgA

• heavy chain

• light chain

• joining chain - not found in serum IgA

• secretory component - not found in serum IgA

which glands have the highest secretory IgA

saliva in minor salivary glands have the highest level of secretory IgA

when are levels of sIgA highest

• highest levels in the morning

• lowest levels in the evening

» follows circadian rhythm (gradually decreases as day goes on)

why do levels of sIgA vary

• levels vary in response to physical and psychological stress through interactions with the autonomic nervous system

• also affected by flow rates - concentration normally decreases as flow rates increase

outline IgG

• derived from serum

• mainly neutralises and inhibits microbial adhesion

• may opsonise

outline the function of alpha amylase

• enzyme that degrades starches to amylose and amylopectin (polysaccharides)

• causing release of a sweet taste

what is the structure of amylose

• linear, unbranched chain of alpha glucose

• coiled structure

• D-glucose molecules in an alpha 1,4 linkage

what is the structure of amylopectin

• long chain

• branched chain with alpha 1,6 linkages

what are dextrins

short chains of glucose units resulting from starch breakdown

what stimulus increases the levels of salivary alpha amylase

stress - action of sympathetic nervous system

which salivary proteins are involved in enamel protection

• statherin

• proline rich proteins

• cystatins

outline statherin

• inhibits CaPO₄ precipitation and crystal growth (component of pellicle)

• helps maintain Ca²⁺ supersaturation

outline proline rich proteins

• glycosylated form - lubrication

• acidic form - inhibits CaPO₄ precipitation

• mediates bacterial adhesion

• binds to tannins

outline cystatins

• cysteine rich proteins

• inhibits CaPO₄ precipitation

• inhibits cysteine proteases

which salivary proteins help remineralisation and how do they do so

• PRPs and statherin helps remineralisation

  • they keep enamel pores open so calcium and phosphate ions can diffuse into enamel

do PRPs and statherin prevent calculus formation

• no

• because they are not found in plaque so if degraded, does not prevent calculus formation

why is saliva an effective diagnostic tool

• non-invasive

• rapid

• cost-effective

• precise

• simple

what conditions can saliva be used to test for

• stress

• Alzheimer’s

• Parkinson’s

• sleep disorders

• TB

• periodontal disease - based on IL-1 protein

• concussion