Biology of Streptococcus mutans-Derived Glucosyltransferases: Role in Extracellular Matrix Formation of Cariogenic Biofilms

The importance of Streptococcus mutans in the etiology and pathogenesis of dental caries is certainly controversial, in part because excessive attention is paid to the numbers of S. mutans and acid production while the matrix within dental plaque has been neglected. S. mutans does not always dominate within plaque; many organisms are equally acidogenic and aciduric. It is also recognized that glucosyltransferases from S. mutans (Gtfs) play critical roles in the development of virulent dental plaque. Gtfs adsorb to enamel synthesizing glucans in situ, providing sites for avid colonization by microorganisms and an insoluble matrix for plaque. Gtfs also adsorb to surfaces of other oral microorganisms converting them to glucan producers. S. mutans expresses 3 genetically distinct Gtfs; each appears to play a different but overlapping role in the formation of virulent plaque. GtfC is adsorbed to enamel within pellicle whereas GtfB binds avidly to bacteria promoting tight cell clustering, and enhancing cohesion of plaque. GtfD forms a soluble, readily metabolizable polysaccharide and acts as a primer for GtfB. The behavior of soluble Gtfs does not mirror that observed with surface-adsorbed enzymes. Furthermore, the structure of polysaccharide matrix changes over time as a result of the action of mutanases and dextranases within plaque. Gtfs at distinct loci offer chemotherapeutic targets to prevent caries. Nevertheless, agents that inhibit Gtfs in solution frequently have a reduced or no effect on adsorbed enzymes. Clearly, conformational changes and reactions of Gtfs on surfaces are complex and modulate the pathogenesis of dental caries in situ, deserving further investigation

Role of asparagine 1134 in glucosidic bond and transglycosylation specificity of reuteransucrase from Lactobacillus reuteri 121

Glucansucrases from lactic acid bacteria convert sucrose into various α-glucans that differ greatly with respect to the glucosidic bonds present (e.g. dextran, mutan, alternan and reuteran). This study aimed to identify the structural features of the reuteransucrase from Lactobacillus reuteri 121 (GTFA) that determine its reaction specificity. We here report a detailed mutational analysis of a conserved region immediately next to the catalytic Asp1133 (putative transition-state stabilizing) residue in GTFA. The data show that Asn1134 is the main determinant of glucosidic bond product specificity in this reuteransucrase. Furthermore, mutations at this position greatly influenced the hydrolysis/transglycosylation ratio. Changes in this amino acid expands the range of glucan and gluco-oligosaccharide products synthesized from sucrose by mutant GTFA enzymes.

Lipase-Catalyzed Synthesis of Fatty Acid Esters of Trisaccharides

First Online: 15 August 2018.-- Sandoval G. (eds).Carbohydrate fatty acid esters have a broad spectrum of applications in the food, cosmetic, and pharmaceutical industries. The enzyme-catalyzed acylation is significantly more selective than the chemical process and is carried out at milder conditions. Compared with mono- and disaccharides, the acylation of trisaccharides has been less studied. However, trisaccharide esters display notable bioactive properties, probably due to the higher hydrophilicity of the sugar head group. In this chapter, we describe the acylation of two trisaccharides, maltotriose and 1-kestose, catalyzed by different immobilized lipases, using vinyl esters as acyl donors. To illustrate the potential of such compounds, the antitumor activity of 6″-O-palmitoyl-maltotriose is shown.We thank CONACYT (Mexico) and Kuragobiotek Holdings for the economic support received. The projects BIO2013-48779-C4-1-R and BIO2016-76601-C3-1-R from the Spanish Ministry of Economy and Competitiveness also supported this research.Peer reviewe