T3A1 Flashcards
Lactose
a sugar that is common in milk and dairy products, can serve as a primary energy source
Lactase role
B-galactosidase hydrolyzes lactose to the monosaccharides glucose and galactose
Lactase present on
apical surface of absorptive intestinal enterocyte cells
Galactose gets converted into
glucose 6 phosphate
Galactokinase
enzyme that adds phosphate group to proteins
Gal-1-P Uridyltransferase and UDP-Gal Epimerase are
Galactose to glucose enzymes
Weaning
- adult mammals other than humans lactase production decreases significantly (environmental factors)
- 65% humans have reduced ability to digest lactose after weaning
Mutations that keep lactase gene permanently on common in
individuals whose ancestors has access to domesticated dairy animals
- 7500-9000 years ago in middle east and north africa, then brought to europe
Lactase mutations arose in what gene?
MCM6 (enhances lactase gene transcription through lifetime)
90% lactase gene expression through whole life populations
Swedes, Danes, pastoralist African
50% lactase gene expression through whole life populations
Spanish, French, Pastoralist Arab
Low in lactase gene expression through whole life populations
non-pastoralist Asian and African
Lactose intolerance
individuals born without the ability to express lactase gene that codes for lactase protein - congenital lactose deficiency
Lactose intolerance results
excessive lactose in intestine attracts water molecules, which prevents water from being properly absorbed into bloodstream. Bacteria ferments > bloating, diarrhea, dehydration
LCT gene on chromosome 2 codes for lactase enzyme > mutations in coding region
changes that alter single amino acids or lead to polypeptides that are too short
Galactosemia
galactose in the blood, individuals born without enzymes needed for galactose processing
Galactosemia type I gene
GALT gene (Galactose-1-phosphate uridylyltransferase)
Galactosemia type II gene
GALK1 gene (Galactokinase)
Galactosemia type III gene
UDP-Gal Epimerase
Galactosemia mutations in what genes?
GALT, GALE, GALK1 and genes on chromosome 9. Alter single amino acids or polypeptides too short
Galactosemia effects
toxic accumulation of galactose. Cataracts, kidneys, liver affected
Galactosemia clinical landmark
jaundice
Lactose intolerance treatment
- omitting lactose
- pretreating milk with purified lactase
Galactosemia treatment
omitting galactose consumption
Who pioneered the original modern hypothesis of the positive role of certain bacteria
Elie Metchnikoff
Elie Metchnikoff observed
populations in rural Europe that lived on fermented milk exceptionally long lived
Milk fermented with lactic acid producing bacteria inhibits
growth of proteolytic bacteria due to low pH produced by fermentation of lactose
Lactic acid producing bacteria
Lactobacillus
Lactococcus
Bfidobacteria
What does lactic acid producing bacteria do?
ferment carbs in milk (lactose>glucose and galactose)
Microbial B-galactosidase in yogurt is present
in active forms in duodenum
B-galactosidase enhances
lactose metabolism in lactase deficient individuals
Low pH environments reduce
enzyme activity (irreversible denaturing)
How does enzyme retain function in duodenum after passing through stomach?
protection by bacterial cell membrane
buffering capacity of yogurt
pH of stomach while yogurt passing through
4
Can lactase enzyme supplement help people experiment
after 4 people were given treatments to modify intestine bacterial contents (yogurt, capsules, mix of bacterial strains), measured feces, bifidobacteria has made it through.
Can lactase enzyme supplement help people results
supplementation with probiotics modified amount of bacteria and increased bgalac in feces of lactose intolerant subjects. probiotic cannot stimulate endogenous intestinal lactase enzyme activity in small intestine
