Biochemistry of saliva

• Objectives

• Describe the composition of saliva

• Mention its functions

Dr/ Ragaa Salama 1

Dr/ Ragaa Salama

Clinical Highlights

• Understanding of salivary mechanisms prerequisite for – effective treatment of salivary gland

dysfunctions– modulation of bacterial colonization– development of artificial saliva

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Dr/ Ragaa Salama

Saliva Definition: Secretions of salivary glands (parotid and

submandibular/sublingual) Composition of Saliva : 4 major components

1-mucus that serves as a lubricant. 2-amylase →initiates the digestion of starch. 3-lingual lipase → begins digestion of fat. 4-electrolyte solution (Na+,Cl- , K+, HCO3- → moistens food. 5-proteins& enzymes: Statherins, Proline-rich

Proteins (PRPs), Histatins, Cystatins, Lysozyme, Salivary peroxidase

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Dr/ Ragaa Salama

saliva is hypotonic to plasma -Na+ and Cl- ↓ in saliva than plasma -K+ and HCO3- ↑in saliva than in

plasma. - pH changes from being slightly

acidic (pH 6-7 ,at rest) to basic (pH 8) at ultimate stimulation ↑ ↑ HCO3- in the saliva

-Amylase and mucus also increase in concentration after stimulation.

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Dr/ Ragaa Salama

functions of saliva

SalivarySalivaryFamiliesFamilies

Anti-Anti-BacterialBacterial

BufferingBuffering

DigestionDigestion

Mineral-Mineral-izationization

Lubricat-Lubricat-ion &Visco-ion &Visco-elasticityelasticity

TissueTissueCoatingCoating

Anti-Anti-FungalFungal

Anti-Anti-ViralViral

Carbonic anhydrases,Carbonic anhydrases,HistatinsHistatins

Amylases,Amylases,Mucins, LipaseMucins, Lipase

Cystatins,Cystatins,Histatins, Proline-Histatins, Proline-rich proteins,rich proteins,StatherinsStatherins

Mucins, StatherinsMucins, Statherins

Amylases, Cystatins, Mucins, Amylases, Cystatins, Mucins, Proline-rich proteins, StatherinsProline-rich proteins, Statherins

HistatinsHistatins

Cystatins,Cystatins,MucinsMucins

Amylases, Cystatins,Amylases, Cystatins,Histatins, Mucins,Histatins, Mucins,PeroxidasesPeroxidases

Dr/ Ragaa Salama

Mucin Functions• Tissue Coating

– Protective coating about hard and soft tissues– Primary role in formation of acquired pellicle– Concentrates anti-microbial molecules at mucosal interface

• Lubrication– Increases lubricating qualities (film strength)

• Aggregation of bacterial cells– Bacterial adhere to mucins may result in surface attachment, or– Mucin-coated bacteria may be unable to attach to surface

• Bacterial adhesion– React with bacterial adhesins, thereby blocking them

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Dr/ Ragaa Salama

Amylases

• digestive function• Hydrolyzes starches → amylose ,amylopectin,Maltose ,glucose,• in tears, serum, bronchial, and male and female urogenital

secretions• role in modulating bacterial adherence

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Dr/ Ragaa Salama

Lingual Lipase• Secreted by von Ebner’s glands of tongue

• Involved in first phase of fat digestion

• Hydrolyzes medium- to long-chain triglycerides

• Important in digestion of milk fat in new-born

• highly hydrophobic enters fat globules

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Dr/ Ragaa Salama

Statherins• Produced by acinar cells in salivary glands

• Statherins prevent precipitation or crystallization of supersaturated calcium phosphate in ductal saliva and oral fluid

• Lubricant.

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Dr/ Ragaa Salama

Proline-rich Proteins (PRPs)• Inhibitors of calcium phosphate crystal

growth

• Present in the initially formed enamel pellicle and in “mature” pellicles

• Acquired enamel pellicle is 0.1-1.0 µm thick layer of macromolecular material on the dental mineral surface

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Dr/ Ragaa Salama

Histatins• A group of small histidine-rich proteins

• Potent inhibitors of Candida albicans growth

Cystatins•Are inhibitors of cysteine-proteases

•protective against unwanted proteolysis (bacterial proteases, lysed leukocytes)

•inhibit proteases in periodontal tissues

•effect on calcium phosphate precipitation

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Dr/ Ragaa Salama

Lysozyme ( LZ )• Present in numerous organs and most body fluids• Oral LZ is derived from at least four sources

– major and minor salivary glands, phagocytic cells and gingival crevicular fluid (GCF)

• Biological function• anti-microbial activity by:• Inhibition of bacterial adhesion to tooth surfaces• Inhibition of glucose uptake and acid production• Muramidase activity (lysis of peptidoglycan layer)

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Dr/ Ragaa Salama

Salivary peroxidase systems• Sialoperoxidase (SP, salivary peroxidase)

– Readily adsorbed to various surfaces of mouth• enamel, salivary sediment, bacteria, dental plaque

• Myeloperoxidase (MP)– From leukocytes entering via gingival crevice– 15-20% of total peroxidase in whole saliva

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Dr/ Ragaa Salama

Regulation of oral microorganisms by SP/MP

UnstimulatedUnstimulated

bacteriabacteria

InhibitedInhibitedbacteriabacteria

ActiveActivebacteriabacteria

Food IngestionFood Ingestioncarbohydratescarbohydrates

StimulationStimulationStimulationStimulation

MetabolismMetabolismMetabolismMetabolism

HH++

RecoveryRecoveryRecoveryRecovery

OO22

thiolsthiols

InhibitionInhibitionInhibitionInhibition

Salivary GlandsSalivary GlandsSalivary GlandsSalivary Glands

SCNSCN-- + H + H22OO22

OSCNOSCN--/HOSCN/HOSCN

AutoinhibitionAutoinhibition

spontaneousspontaneous

+SP+SP14

Dr/ Ragaa Salama

Other anti-microbial activities of LZ

• Muramidase activity (lysis of peptidoglycan layer)

• Cationic-dependent activation of bacterial autolysins

• Aggregation of bacteria

• Inhibition of bacterial adhesion to tooth surfaces

• Inhibition of glucose uptake and acid production

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Dr/ Ragaa Salama

Anti-microbial activities of saliva

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• thiocyanate ions and another• is several proteolytic enzymes—most important,• lysozyme—that (a) attack the bacteria, (b) aid the thiocyanate• ions in entering the bacteria where these ions• in turn become bactericidal, and (c) digest food particles,• thus helping further to remove the bacterial metabolic• support.• protein antibodies that can destroy oral bacteria

Dr/ Ragaa Salama 17