Introduction
Shayne C. Gad in Toxicology of the Gastrointestinal Tract, 2018
The water in saliva provides a medium for dissolving foods so that they can be tasted and digestive reactions can begin. Chloride ions in the saliva activate salivary amylase. Bicarbonate and phosphate ions buffer acidic foods that enter the mouth; as a result, saliva is only slightly acidic (pH 6.35–6.85). Urea and uric acid are found in saliva because salivary glands (like the sweat glands of the skin) help remove waste molecules from the body. Mucus lubricates the food so it can easily be moved about in the mouth, formed into a ball, and swallowed. Immunoglobulin A (IgA) is a secreted type of antibody that prevents attachment of microbes so they cannot penetrate the epithelium. The enzyme lysozyme kills bacteria. Even though these substances help protect the mucous membrane from infection and the teeth from decay, they are not present in large enough quantities to eliminate all oral bacteria.
Dental Caries: Resistance Factors — Enamel Chemistry and Saliva
Lars Granath, William D. McHugh in Systematized Prevention of Oral Disease: Theory and Practice, 2019
Three nonimmunological glycoproteins which have been identified as potential salivary defense factors are lysozyme, lactoperoxidase, and lactoferrin.8 Lysozyme is present in all body fluids and can cause cell wall disruption which leads to cell death. However, few species of bacteria have been shown to be susceptible to lysis by this substance under normal oral conditions. Lysozyme can still be bactericidal and cause aggregation without lysis, but its role in preventing caries is as yet equivocal. The lactoperoxidase system has been shown to inhibit growth and acid production by a number of organisms including streptococci and lactobacilli and reduce plaque accumulation.41 Lactoferrin is an iron-binding protein capable of exerting a bactericidal effect on several organisms including S. mutans.8 It has been postulated to enhance the antibacterial effect of lysozyme. These three antibacterial substances may act in concert with immunological factors to reduce the cariogenic challenge.
Phagocytosis By Human Neutrophils
Hans H. Gadebusch in Phagocytes and Cellular Immunity, 2020
Finally, there are a large number of acid hydrolases present in the azurophil granules that give this the characteristics of a true lysosome.337,339 These include acid phosphatases, nucleases, a wide variety of carbohydrases, proteases, phospholipase, 0-glucuronidase, neuraminidase, and arylsulfatase. Thus, the cell has the enzymatic capability for hydrolyzing virtually every type of biological compound. The function of these enzymes is generally considered to be digestive in nature, but they may also play a part in the actual bactericidal events. Neeman et al.340 have demonstrated that extracts of neutrophils are highly lytic toward several 14C-labeled bacteria with maximal activity seen at a pH of 5.0. This lytic effect is enhanced by lysozyme. Lahav et al.341 have extended these observations and shown that the effect is selective; some strains of bacteria, e.g., S. albus, are highly susceptible to lysis while others, e.g., group A Streptococcus are quite resistant.
Oral mucosa grafting in periorbital reconstruction
Published in Orbit, 2018
Andre Grixti, Raman Malhotra
MSG secretions are predominantly mucous or seromucinous, similar to natural tears.31,80 Mucin lubricates the ocular surface and coats the epithelium, reducing the high surface tension of the eye forming a more stable and durable wet layer. Mucins prevent evaporation of tears by forming a hydrophobic barrier along the lid margin and increase the tear film break-up time.31,68,71 High levels of antimicrobial proteins such as immunoglobulin A (IgA), lactoferrin, lysozyme, and human beta-defensin (hBD) are present in saliva and protect the ocular surface from infection. Labial MSGs are responsible for one-third of salivary IgA secretion and are the main source of Ig A in the oral cavity. IgA is immunologically active against viruses and bacteria, while lactoferrin acts as an iron chelating agent which inhibits bacterial growth. Lysozyme triggers bacterial agglutination and causes lysis of the bacterial cell wall through autolysin activation.68,80 MSGs secretions contain growth factors including epidermal growth factor and transforming growth factor-β, which promote normal growth and differentiation of the ocular surface epithelium as well as corneal reepithelization.31,90 Saliva plays a significant role in the digestion of carbohydrates and fats and is rich in two enzymes, ptyalin, an α-amylase, and lingual lipase. Bennett 91 did not identify any deleterious effect on the ocular surface from ptyalin because of its substrate specificity to polysaccharides.
Saliva proteomic profile of early childhood caries and caries-free children
Published in Acta Odontologica Scandinavica, 2023
Bethania Paludo Oliveira, Marília Afonso Rabelo Buzalaf, Natália Caldeira Silva, Talita Mendes Oliveira Ventura, Júlia Toniolo, Jonas Almeida Rodrigues
Lysozyme, Lysozyme C, Histones and Prolactin-inducible protein (PIP) were up-regulated in the ECC group. The higher level of Lysozyme in the ECC group may suggest a compensatory protective mechanism. In specific situations, such as in caries disease or high levels of S. mutans, Lysozyme secretion is stimulated [37]. Similar results for Lysozyme C were reported previously [31]. However, a recent study on the activity and distribution of pellicle enzymes, such as Lysozyme, in children did not reveal significant differences in enzyme activity associated with children’s caries activity [30]. Although, it is important to emphasize that the analysis of pellicles may not be used as a predictor of metabolite concentrations in saliva and vice versa. The formation of pellicles seems to be a specific process. Not all analytes found in saliva are detectable in the pellicle, and the ratio of analytes also differs in the saliva and in the AEP [38].
Lysozyme amyloidosis—a report on a large German cohort and the characterisation of a novel amyloidogenic lysozyme gene variant
Published in Amyloid, 2022
Sophie Anker, Katrin Hinderhofer, Julian Baur, Christian Haupt, Christoph Röcken, Jörg Beimler, Martin Zeier, Markus Weiler, Elke Wühl, Christoph Kimmich, Stefan Schönland, Ute Hegenbart
Human lysozyme is a globular folded protein that consists of 130 amino acids interconnected via four disulphide bridges. Its secondary structure elements are organised in two different structural domains, the α-domain which contains four helices, and the β-domain consisting of a β-sheet and a long loop [6]. All known amyloidogenic variants are located within the β-domain [6]. Detailed studies have been conducted on the effects of the variants on the protein properties, including its folding, stability, and aggregation behaviour to understand the molecular mechanism of lysozyme deposition [6–11]. The general concept emerging from these studies is that amyloid formation of lysozyme originates from a significant reduction in the stability and global cooperativity of the protein structure, which primarily results in the formation of aggregation-prone partially unfolded species [6].
Related Knowledge Centers
- Breast Milk
- Innate Immune System
- Lysis
- Mucus
- Secretion
- Saliva
- Antimicrobial
- Glycoside Hydrolase
- Gram-Positive Bacteria
- Tears