REGULATION OF SUGAR TRANSPORT AND METABOLISM IN LACTIC ACID AND ORAL BACTERIA

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The primary goal(s) of this program are to understand the molecular basis, and the roles of microorganisms in the etiology and pathogenesis of oral diseases. The products of microbial metabolism, including organic acids and sulfur-containing compounds, are either causative or contributory agents to the development of dental caries, gingivitis and periodontitis. Consequently, our research efforts are concerned with the elucidation of the biochemical, enzymatic, and genetic factors, responsible for the fermentation of sugars and amino acids by oral microorganisms. Major accomplishments during the past year include: 1. The identification of a novel phosphoenolpyruvate-dependent maltose:phosphotransferase system in Fusobacterium mortiferum. 2. The purification to homogeneity of two enzymes required for the metabolism of sugars by lactic acid bacteria. Fructokinase II catalyzes the ATP-dependent phosphorylation of fructose, whereas triosephosphate isomerase is a key enzyme for the fermentation of sugars via the Embden-Meyerhof-Parnas (glycolytic) pathway. 3. Site-directed mutagenesis has facilitated identification of substrate binding and catalytically functional residues in N5- (carboxyethyl)ornithine synthase. 4. Beta-Cystathionase has been purified, cloned and sequenced from Bordetella avium. The biochemical basis for the toxicity of this (pyridoxal-phosphate containing) protein toward osteogenic cells has been established. Site-directed mutagenesis experiments have provided evidence for participation of the lysyl residue K214 in co-factor binding, and for the role(s) of cysteine residues in the catalytic process. 5. Antibodies prepared against Beta-cystathionase from B. avium have been used to screen for the same (or, related) enzyme(s) in extracts of oral pathogens including Fusobacteria and Bacteroides species. Results from this research program have been published in peer- reviewed Journals, and have also been discussed in a textbook chapter dealing with the regulation of sugar transport and metabolism by lactic acid bacteria.