vitamin B6 pyrodoxine Flashcards
what is vitamin b6 originally described as?
anti-dermatitis and anti-anemia factor
what are symptoms of b6 pyridoxine deficiency?
seborrheic dermatitis (flaky scales), microcytic anemia, depression, confusion, seizures
What are pyridoxine forms?
4 of them, (all 4 forms w/o phosphate bound), animal tissues contain pyridoxal phosphate and pyridoxamin phosphate, but important COENZYME FORM PARTICIPATE IN >100 reactions
What are food sources of B6?
meat, fish, poultry, non citrus fruits, fortified grains, light sensitive and loss of vitamin by heating or leaching into water?
digestion/absorption of b6?
prior to absorption, phosphate group is removed from PLP, PMP; absorption of pyridoxamine, pyridoxal, and pyridoxine in jejunum, non saturable PASSIVE DIFFUSION, carrier. carrier-mediated process for phosphorylated forms described but not yet clear. we need gastric acidity to release the vitamin. and phosphate to absorb it in upper small intestine
metabolism of b6?
hepatic metabolism to major coenzyme form
vitamin cannot cross membranes freely, ability of liver to accumulate PLP limited by tissue capacity to bind protein
- -(with high intake, PLP converted to pyridoxal)
- -protein binding protects against loss of phosphate group
BASICALLY you flip off the phosphate and you get a phosphate group back when it comes to the liver, and becomes an active coenzyme. depends on capacity to bind protein.
distribution of B6?
pyridoxal and PLP secreted form liver into circulation? PLP as PLP albumin complex, requires dissociation from albumin and hydrolysis to pyridoxal before taken up tissue
STORAGE AND EXCRETION OF B6
primarily in skeletal muscle
bound to glycogen phosphorylase (enzymes that helps break down glycogen to get energy out of glycogen stores), excreted in urine, but some in stool
functions of b6
coenzyme form pyridoxal phosphate participates in >100 reactions in protein and 1-carbon metabolism
transamination, deamination reactions
decarboxylation
heme synthesis – synthesis of mitochondcrial gamma-aminolevulinate is rat e limiting step
one carbon metabolism(methionine synthase pathway)
carb and lipid metabolism
NT synthesis
glycogen to glucose needs b6(remember it comes from liver), all AA rxns too
inflammation impact on B6
alters metabolism and distribution of b6, causing lower PLP in blood –> muscle PLP unaffected, due to hypoalbuminemia, but varied hepatic handling of PLP
health effects of bb6?
low b6 associated with CVD, lung cancer, reduced elderly cognition, malabsorption –> supplementation may benefit pregnancy morning sickness
b6 summary?
bioavailability is high, anemia of b6 deficiency is microcytic compared to b12 and folate, stored in muscle, UL due to potential toxicity
