Caries enzymes

Molybdenum, recognized as an essential trace element for plants, animals, and most bacteria, is present in a variety of metaHo enzymes (44—46). Indeed, the absence of Mo, and in particular its co-factor, in humans leads to severe debility or early death (47,48). Molybdenum in the diet has been impHcated as having a role in lowering the incidence of dental caries and in the prevention of certain cancers (49,50). To aid the growth of plants. Mo has been used as a fertilizer and as a coating for legume seeds (51,52) (see FERTILIZERS Mineral NUTRIENTS). 

Mutans streptococci are the major pathogenic organisms of dental caries in humans. The pathogenicity is closely related to production of extracellular, water-insoluble glucans from sucrose by glucosyltransferase and acid release from various fermentable sugars. Poly(catechin) obtained by HRP catalyst in a phosphate buffer (pH 6) markedly inhibited glucosyltransferase from Streptococcus sorbrinus 6715, whereas the inhibitory effect of catechin for this enzyme was very low. 

An excess of zinc will cause problems in humans. Excessive doses can lead to biochemical control system damage, while doses slightly higher than optimal can cause disorders in iron and copper metabolism, resulting in incurable anemia, decrease in activity of zinc protein enzymes, and pancreas and kidney damage (Boularbah et ah, 1999 Seiler et ah, 1994). Increased levels of zinc have been observed in nuclei of neoplastic cells and in cases of acute dental caries, however its role in these diseases has not been explained. 

Clarkson BH, Hall DL, Heilman JR and Wefel JS (1986) Effect of proteolytic enzymes on caries lesion formation in vitro. J Oral Pathol 15, 423-429. 

Cimasoni G, ishikawa i and Jaccard F (1977) Enzyme activity in the gingival crevice, in The borderland between caries and periodontal disease (ed. Lehner T), pp. 13-41. Academic, London UK. 

In Chapter 5, it is concluded that release of intracellular bacterial metabolites after cell lysis may have been responsible for fhe increases in advanced Maillard products. Lysis of bacteria can deliberately be induced by, for example, lysogenic enzymes and phages. In addifion fo fhe direcf targeting of cariogenic microorganisms, lysis could thus contribute indirectly to caries arrestment by causing an extensive Maillard reaction. However, the problem of the concomitant unaesthetic discoloration will need to be considered before practical application becomes feasible. 

Aside from the Maillard reaction, other covalent modifications of amino acids and proteins are possible within the caries lesion, which merit future investigation. For example, certain oral microorganisms excrete y-glutamyl transferases. These enzymes catalyse the formation of cross-links between glutamic acid and lysine residues of proteins. In addition, N-acyl amino acids are present in plaque, which adsorb to mineral surfaces. 

Unfortunately, however, there is evidence that achieving sufficient fluoride levels in vivo to impair enzyme activity and inhibit bacterial growth is difficult [44], It may therefore be that such potential action of fluoride, for example on car-iogenic bacteria such as S. mutans, has little or no part to play in practical caries prevention. 

Fluoride therapy and fluoridation of drinking water has played a significant role in deccreasing the dental caries. The incidence of dental caries can be significantly decreased by adding fluorides into the drinking water supply. Fluorides prevent decalcification of the structure of tooth by inhibiting bacterial enzymes which produce lactic acid. Fluorides also increase the tooth resistance to acid decalcification. 

Sucrose and Dental Caries The most prevalent infection in humans worldwide is dental caries, which stems from the colonization and destruction of tooth enamel by a variety of acidifying microorganisms. These organisms synthesize and live within a water-insoluble network of dextrans, called dental plaque, composed of (al 6)-linked polymers of glucose with many (a 1 >3) branch points. Polymerization of dextran requires dietary sucrose, and the reaction is catalyzed by a bacterial enzyme, dextran-sucrose glucosyltransferase. 

The pathogenesis of dental caries may involve three distinct processes (1) adherence of the bacteria to the tooth, (2) formation of glycocalyx due to synthesis of a sticky glucan by the action of the bacterial enzyme glucosyl transferase on sucrose, and (3) accumulation of biobUm (plaque), within which there is continuing acid production by constituent bacteria (including streptococci and lactobacflli) able to metabolize carbohydrates at low pH values. This acid demineralizes an enamel. 

Harteneck C, Wedel B, Koesling D, Malkewitz J, Bohme E, Schultz G. Molecular cloning and expression of a new alpha-subunit of soluble guanylyl cyclase. Interchangeability of the alpha-subunits of the enzyme. FEES Lett. 1991 292 217-222. Cary SP, Winger JA, Derbyshire ER, Marietta MA. Nitric oxide signaling no longer simply on or off. Trends Biochem. Sci. 2006 31 231-239. 

Fig. 28. Hate of deacetylation of C -labeled acetylchymotrypsin (ACHT). (A) Acetylchymotrypsin prepared from NBS-oxidized enzyme with 47% of original activity (B) acetylchymotrypsin prepared from NBS-oxidized enzyme with 10% activity (C) acetylchymotrypsin from unoxidized enzyme. O, buffer pH 8.0 A> buffer pH 8.0 containing ATEE (fifty-fold molar excess of ATEE over the enzyme). The C -content of the various trichloroacetic acid (TCA) precipitates appears to be a true measure of the deacetylation process prior to the addition of TCA. Further dialysis of acid solutions of TCA precipitates against dilute HCl did not lead to any significant change in the C -activity. (D) Appearance of enzyme activity. Acetylchymotrypsin added to a solution of ATEE of pH 8.0 (the figure shown is traced from the actual record of the Cary spectrophotometer). ATEE, 2 X 10 Af ACHT, 10 yug pH 8.0. From Viswanatha and Lawson (1961).

Few studies have investigated links between salivary enzymes and caries or calculus. Neither Ruan et al. [97] nor Stuchell and Mandel [114] could find differences in lysozyme levels between caries-resistant and caries-susceptible subjects. On the other hand, Mandel [84] found significantly less lysozyme in submandibular saliva from heavy calculus-formers than from non-calculus formers, and a similar trend in acid phosphatase level was almost significant. Mandel speculated that lysozyme, by its interaction with cell walls [106], might modify initial calcification processes. 

Fluorine is present on earth only as fluoride, a negatively charged anion that is especially important in dentistry because of its ability to mediate protection from dental caries (Chapter 16, section 16.2.1.). Although metabolites of chlorine and iodine are ubiquitous, few biological products contain fluoride because of its tight hydration shell. The few enzymes that utilize fluoride as a cofactor must overcome an exceptionally high desolvation energy barrier. 

Starch and sucrose, key substrates for the development of dental caries, are exclusively synthesized by plants. They are made in plant leaves by a process called photosynthesis, which utilizes sunlight as the energy source. This chapter outlines the light and dark reactions of photosynthesis and compares the light reaction with mitochondrial electron transport (Sect. 1). The key dark reaction, the production of phosphoglycerate by the enzyme ribulose bisphosphate carboxylase (rubisco), is described along with the production of fructose, sucrose, and starch (Sect. 2). The chapter concludes with a detailed discussion of the roles of starch and sucrose in plant metabolism (Sect. 3). 

The salivary glands also secrete urea, which some oral bacteria convert to ammonia and carbon dioxide with an enzyme, urease. The greater content of ammonia results in the oral cavity being better buffered to acids and better protection from caries (Chap. 15, Sect. 3). Calcium and phosphate are also present in saliva at supersaturating concentrations but do not precipitate due to protein chelation. Whole saliva also contains small amounts of various other proteins proteases, protease inhibitors (cystatins), type IV carbonic anhydrase, statherin, histatins, lysozyme, salivary agglutinin, and immunoglobulin A. 

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