Pyridine analogs inhibit the glucosyltransferase of Streptococcus mutans

Abstract

Soluble glucan synthesis catalyzed by dextransucrase preparations from Streptococcus mutans 6715 were inhibited by pyridoxal-5-phosphate and several other pyridine analogs, including pyridoxine, pyridoxamine, pyridoxamine-5-phosphate, pyridoxal, and 4-pyridoxic acid. Pyridine and pyridine-4-carboxaldehyde were not effective inhibitors of the enzyme. Kinetic analyses suggested that pyridoxal-5-phosphate is a noncompetitive inhibitor of dextransucrase. The inactivation was dependent on time, pyridoxal-5-phosphate concentration, and hydrogen ion concentration. Apparent Ki values were 4.9 mM at pH 7.0 and 4.2 mM at pH 5.5. Dextransucrase activity could be restored by dialysis to remove the inhibitors. Maximum inhibition was observed after a 120-min incubation of the enzyme with pyridoxal-5-phosphate. The pH optima for inhibition by pyridoxal-5phosphate were 4 and 7. The sucrose-dependent adherence of S. mutans cells to saliva-coated hydroxylapatite beads was also inhibited by pyridoxal-5-phosphate but only marginally by the other pyridine analogs. In addition, pyridoxal-5phosphate markedly reduced the rate of acid production by intact S. mutans cells from sucrose or glucose substrates. Another pyridoxal-5-phosphate analog, 2methyl-5-hydroxypyridine, was also effective in preventing the production of acid by S. mutans from sucrose or glucose. When S. mutans cells were preincubated with pyridoxal-5-phosphate or pyridine analogs, significant reductions in the rate of D-glucose uptake were observed. It is suggested that the inhibition of dextransucrase occurs because of a change in enzyme conformation which results from the binding of the pyridine derivatives. The results suggest that pyridoxal-5phosphate or structural analogs may ultimately be useful in reducing the incidence of dental caries. Streptococcus mutans is a name given to a group of oral bacteria believed to be involved in

Deficiency of PdxR in Streptococcus mutans affects vitamin B6 metabolism, acid tolerance response and biofilm formation

“…PLP at 10 mM was shown by Thaniyavarn et al . () to reduce Gtf activity in vitro (see below for more), although whether it affects GtfB activity and glucan production at micromolar levels remains unclear. It is also possible that PdxR‐deficiency influences the conformation and/or stability of GtfB protein, which consequently can affect the assembly of glucose polymer and biofilm formation of the deficient mutant.…”

“…It is well documented that micromolar vitamin B 6 is required for S. mutans to grow in chemically defined medium (Carlsson, 1970;Terleckyj et al, 1975). However, there is also evidence that pyridine analogs, including B 6 vitamers, could reduce glucose uptake and inhibit glucosyltransferase activity (Thaniyavarn et al, 1982). In an effort to further investigate the effects of vitamin B 6 on growth and biofilm formation by S. mutans, various concentrations of PL, PM and PN were included in BHI for growth studies and in BMGS for biofilm formation on 96-well plates.…”

“…The gtfB and gtfC genes are known to be linked, but as indicated in multiple reports (Goodman & Gao, 2000;Wen et al, 2005;Bitoun et al, 2013), our results again showed that these two genes could be differentially transcribed under the conditions studied. PLP at 10 mM was shown by Thaniyavarn et al (1982) to reduce Gtf activity in vitro (see below for more), although whether it affects GtfB activity and glucan production at micromolar levels remains unclear. It is also possible that PdxR-deficiency influences the conformation and/or stability of GtfB protein, which consequently can affect the assembly of glucose polymer and biofilm formation of the deficient mutant.…”

Purification, surfactant stabilization, molecular weight studies, and divalent metal ion kinetics of dextransucrase from Leuconostoc mesenteroides NRRL B-512F

“…Pyridoxal phosphate inhibits S. autans glucansucrase in a pure noncompetitive fashion [332]. The inhibition, which reaches 99+% at 30 mM pyridoxal phosphate, requires 2 h preincubation with the enzyme to develop fully and is reversed by dialysis.…”

“…The inhibition, which reaches 99+% at 30 mM pyridoxal phosphate, requires 2 h preincubation with the enzyme to develop fully and is reversed by dialysis. Other pyridine analogs than pyridoxal phosphate, such as 4-pyridoxic acid and 3-hydroxypyridine, are also inhibitory [332], although they do not contain aldehyde groups.…”