L5 Glycan Metabolism Flashcards
Where do glycans get broken down
Colon
Whaf is dietary fibre eg from plants
Glycans which are indigestible by our enzymes
Gice some plant cell wall polysaccharides
Xylan
Pectin
Are plant cell wall glycans soluble or insoluble
Both
Give some oligo saccharide vegetable examples
Broccoli and beans have raffinose
What type of starch isnt digested by our amylqses
Resistant starch
What are fructans and where can you find them
Fructose polysaccharides wg in garlic but also put into probiotics
What process produces waste products scfa
Anaerobic fermentation
What are the 3 types of scfa and who makes them
Butyrate - firmicutes
Proprionate- bacteroidetes
Acetate- all
What are the major functions of butyrate by firmicutes
Anti cancer effects and providing energy for colonocytes
What are the major functions of proprionate by bacteroidetes
Anti inflam (smith et al 2013)
Glucose homeostasis
Reduce appetite
What is the function of acetate
Lower ph to block pathogens
Also affects lipogenesis
Which article discusses butyrate anti cancer functions
Chen et al 2018
What does chen et al 2018 outline
By blocking hdacs, butyrate hyperacetylayes histones which helps regulate apoptotic and cell survival enzymes
Interferes with apoptotic pathways
Why does ulcerstive colitis occur in rectum and distal colon
Lower levels of scfa there
Why is there a smaller mucus layer with mucin in si and stomach
Erosion due to lack of anaerobic fermembration there for glycan utilisation so they start to use mucins
Which articel outlines wrosion of mucin layer due ti low dietary fibre
Desai 2017
Give an example of bacteria which can utilise o glycan mucins (desai 2017)
Bacteroides theta
What does muc2 deficiency on epi cells cause
Colon cancer and inflammation (desai 2017)
What happens where theres low fietary fibre to the microbiota diversity which happens in ibd
The mucin utlising bacteria outcompete the rest (usually bacteroides)
Why can some utlisie mucins
Express cazymes which can degrade mucus polysaccharides
Give some examples bacteroidetes (-)
Bacteroides theta,ovatus,fragilis, prevotella
Give some dxamples of firmicutes (+)
Clostridium, roseburia, eubacterium
Which other bacteria are for fermentation
Actinobscteria like bifido
Which bacteria tend to have more specialised roles
Firmicutes and actino
What bacteroides prefer mucins for energy
B. Thetaiotaomicron
Which bacteroides prefer plant polysaccharides like xylan
Bacteroides ovatus
Can bacteroides use mog
Yes
Which part of genome is responsible for bacteroidetes utlisation of glycan from OM
Puls - polysaccharide utilisation loci
What do puls encode
Different SUS like systems (starch utilisation systems) which allow import and degradation of glycans.
Why is there many puls
Nrcause many different sus like systems speicfic for specific glycans
How many puls do b thetaiotaomicron encode
88 for diff glycans
What sus protein is the importer transembrane protein
Sus C
What does sus c form complex with and why
Sus d lipoprotein which bunds glycan larger than 5 sugars long. Sits on top of sus C like a lid
What is sus G like proteuns
The surface enzymes hsed to degrade larger polysaccharides into smaller
What enzyme is susG
Gh13 for starch
What associates with sus c and d which allows sensing of glycans by bacteroidetes
The sensor regulators all for diff glycans
What do glycans further get degraded by from puls
Periplasmic enzymes
What is needed on c/d complex ti bind glycans wkth high affinity unlike susD so that glycans wre available
SGBP - surface glycan binding proteins (SusE like)
Give an exmaple of a surface cazyme needed for the cd mechanism
B theta need dextranase to breakdown dextran so rhag it gets imported. Witjout it the b theta couldnt grow
Why are firmicutes more specialised
Less gh and pl
What type of mechanism instwad of puls do firmicutes have
Abc atp birning cassettes on inner mmebrnae usint atp hydrlysis
In larhe cell wall have Glycanases like gh13 for starch. Theyre upregulated accordingly
What do the glycanssws in cell walls of firmicutes have to bind glycans
Carbohydrate binding molrcules CBM
What do firmicutes prefer over bacteroidetes and give an exmaple
Insoluble polysaccharides. Eg ruminococci have multienzyme complexes which breakdown starch and cellulose called cellulosome and amylosome
Which bacteria need firmicutes and bacteroudetes ti break down poly into okigo for use
Bifidonacterium
Do bifido have similar to abc transporter mechanism
Yes. Rhey also have glycansses and the surface binding proteins
What is the bifido interaction with f and b called
Cross feeding
Give an example of how bacteroides ovatus is used to co culture bifido asolescentis on simple xylans/ wheat
B ovatus can utlisie complrx and simple wheat xylans from planr polysaccharides. This breakdown into simple oligo xylans can be used to grow bifido adolescentis
