Regulation of Glucosyl- and Fructosyltransferase Synthesis by Continuous Cultures of Streptococcus mutans

Abstract

117Streptococcus mutans strain Ingbritt, and its derivative B7 which had been passaged through monkeys, have been used to investigate how the synthesis of extracellular glucosyl-and fructosyltransferases is regulated. The most active enzyme from carbon-limited continuous cultures was a fructosyltransferase ; enzymes catalysing the formation of water-insoluble glucans from sucrose were relatively inactive. Dextransucrase (EC 2.4.1 .5), which catalyses soluble glucan synthesis, was most active in the supernatant fluid from cultures grown with excess glucose, fructose or sucrose, but full activity was detected only when the enzyme was incubated with both sucrose and dextran. Little dextransucrase activity was detected in carbon-limited cultures. It is concluded that glucosyl-and fructosyltransferases are constitutive enzymes in that they are synthesized at similar rates during growth with an excess of the substrate or of the products of the reactions which they catalyse. Although the Ingbritt strain was originally isolated from a carious lesion, it is now a poor source of glucosyltransferase activity. Glucosyltransferases were extremely active in cultures of a recent clinical isolate, strain 3209, and were apparently induced during growth with excess glucose.

Purification and characterization of an extracellular levansucrase from Pseudomonas syringae pv. phaseolicola

“…This proposal is mainly based on the striking similarity in the Nterminal amino acid sequences of E. amylovora, Z. mobilis, and P. syringae pv. phaseolicola, in contrast to the nearly completely missing similarity to those of the gram-positive bacteria B. subtilis, B. amyloliquefaciens, and S. mutans, which are very similar to each other in activity and sequence (3,43,45,49,51). A comparison of the Z. mobilis and E. amylovora enzymes shows a high similarity in the first 75 amino acids: 55% are identical.…”

“…phaseolicola are of nearly the same molecular weight, about 47,000. Also, all of them are secreted constitutively, in contrast to the mostly substrate-dependent expression of levansucrases in gram-positive bacteria (38,43,51).…”

Multilevel control of extracellular sucrose metabolism in Streptococcus salivarius by sucrose

“…1 l), which partially degrades glucan ; and fructanase (p-D-fructan fructohydrolase; EC 3.2.1.80), which releases free fructose by hydrolysing fructan polymers. Since these enzymes are produced in the absence of substrate, they have been assumed to be constitutive in oral streptococci (Janda & Kuramitsu, 1978;Wenham et al, 1979). Although there have been suggestions in the literature that this might not be the case (Keevil et al, 1983;Walker et al, 1983;Walker & Jacques, 1987), it has been difficult to show conclusively that these enzymes are under any kind of regulatory control.…”

Sequence analysis of the Streptococcus mutans fructosyltransferase gene and flanking regions

“…Growth of S. mutans Ingbritt in continuous culture indicated that the enzyme is constitutively expressed (27). In contrast, another enzyme catalyzing the synthesis of fructan from sucrose, levansucrase from Bacillus subtilis, was shown to be inducible by sucrose (12).…”