MFD 22 Flashcards
Aim • To describe the key components and functions of the extracellular matrix of dental plaque. Content • Exopolysaccharide production. • Fructans • Glucans • Glucan binding proteins • Proteins and Nucleic acids. • Plaque fluid and enamel dissolution.
1) What macromolecules form the basic structure of dental plaque?
2) What Small molecules may be trapped within the matrix (ie the ‘plaque fluid’): ?
1) polysaccharides, proteins, nucleic acids
2) nutrients, metals, signalling molecules
What is responsible for the ‘crystalline’ colony appearance on sucrose-containing agar ?
Exopolysaccharides – glucans and fructans
What are the 2 types of exopolysaccharides?
2) what interesting about them?
3) Where does the energy come from?
1) glucans and fructans
2) they are formed outside the cell, synthetic reactions never occur outside the cell usually as require energy
3) sucrose has a high energy
are the exopolysaccharides soluble or insoluble?
2) What structure do they have?
1) either
2) varies, but very complex
What enzyme is used to make glucans?
Glucosyltransferase (GTF)
What enzyme is used to make fructans?
Fructosyltransferase (FTF)
watch a youtube video on numbering carbons in sugar
go over reactions in glucan synthesis
What is the function of Fructan Polymers: Inulins (β-2,1 bond type, 95%, beta-2,6 bond type 5%) ?
2) What synthesises it?
long term storage carbohydrate instead of starch
2) Only synthesised by Strep. mutans &
some strains of Strep. salivarius
Which is soluble and which is insoluble:
1) Fructan Polymers: Inulins (β-2,1 bond type, 95%, beta-2,6 bond type 5%)
2) Fructan Polymers: Levans (β-2,6 bond type)
1) insoluble
2) soluble
Fructan Polymers: Levans (β-2,6 bond type)
1) Is it made by strep. sanguinis
2) is it made by actinomyces
3) is it made by strep. mutans
4) FUNCTION:
1) yes
2) yes
3) no
4) adheres bacteria together in biofilm, but 1,3-linked, making it insoluble
What are the 2 types of fructan?
1) Levans (β-2,6 bond type) (possible there is a 1,3-linked form that is insoluble)
2) Inulins (β-2,1 bond type)
What is the name of the insoluble glucan polymer?
- water insoluble (mutan)
* core is α-1,3 linked
What the soluble glucan polymers?
- water soluble (dextran)
- core is α-1,6 linked
- many variations!
What is the only substrate for glucan synthesis?
2) Why?
1) sucrose
2) releases a high amount of free energy when bond broken, Free energy in the glycosidic bond of sucrose is 29 kj/mol (equiv. to phosphorylated precursors eg UDP- glucose) ,
energy used to make glycosidic bond in maltose which has a lower kj/mol
What is the common name given to a linear chain fo fructose joined by beta2,1 links?
2) What type of link is the cross links?
1) Inulins
2) beta 2,6 glycosidic bonds
What is the name of a linear polymer of fructose with beta 2,6 links?
2) Why is it called this?
levans
2) rotates polarised to the left
Describe the polymer structure of mutans:
In some bacteria almost entirely alpha 1,3, linear. with a few alpha 1,6 branches.
In other strains, 85%-90% is alpha 1,3 and the rest is alpha 1,6.
Which exopolysaccharide makes up 70% of plaque?
mutans
What makes glucose more cariogenic than sucrose?
glucose can be used to make mutans, which is insoluble so despite being more slowly produced and not forming as much acid per monomer, it has a lower turnover so sticks the bacteria to the teeth better.
1) What glycosidic bond present in dextrans?
2) describe the variation in structure from typical dextras to the one formed by strep sobrinus:
1) alpha- 1,6
2) • side branch is short compared with the backbone
• there is a side branch for about every 15 backbone residues. The side branch is an alpha-1,3 glycosidic bond.
Why is dextrans called dextrans?
rotates polarised light to the right
What adds to the complexity of structure of exopolysaccharides?
as they are synthesized in the external environment, the rate of enzymes is affected by environmental factors.
What can affect glycotransferase (GTFs)?
- presence of glucans ( as can act as an acceptor of unrelated GTF)
- proteseases (may modify GTF) and dextranases
Why are GTF and FTFs names so damn confusing and wird?
2) What should we use instead?
3) list them for step. mutans
name after role however,
A GTF is involved in forming things as well as breakng down sucrose.
There is another naming system to do with solubilities e.g. GTF-S = forms soluble polymer
2) the gene that forms them e.g. in strep mutans there is 3 GTF and 1 FTF. gtfA is not true GTD as makes an ezyme ( sucrose phosphorylase), gtfB makes insoluble mutan , gtfc makes a branched mutan thats partially soluble. gtfD makes a soluble dextran. ftf forms inulin
