B6 Flashcards
Gyorgy
identifies factor that cures dermatitis in
rats, names it Vit B6. Chemical structure= pyridine
derivative with several methoxy groups.
Foods
Beef &
Nuts
Main circulating form=
pyridoxal phosphate (PLP) bound to albumin in plasma
Liver
Converts it
back to PLP
Peripheral tissue uptake
Plasma PLP taken up by muscle.
80-90% in muscle. Bound to glycogen phosphorylase (One
PLP at each of the 2 catalytic sites
Body stores
Body Stores: 60-170 mg
with a half-life of ~25 days.
Excretion
As metabolite 4-pyridoxic acid. ~50 of daily
intake is converted to this. Pyridoxal to 4-pyridoxic acid by
pyridoxal oxidase.
Function
PLP coenzyme in >100 enzymes (nonprotein
compound necessary for the functioning).
Transaminations, decarboxylations, Transfulrations, Rgroup
interconversions. Serine to Glycine by SHMT!
Dopamine
neurotransmitter, important in cognition,
motivation, reward. Motor control. Produced in neurons.
Parkinson’s due to death of neurons. (one of the many
neurotransmitters B6 synthesizes).
Transamination
Key process in AA Degradation.
Catabolism of nearly all amino acids involves transfers of
amino group to α-keto acids.
Major amino group
acceptors:
α-ketoglutarate and pyruvate.
PLP is bound to
the enzyme through
a Schiff base linkage to a Lys residue
at the active site.
Heme biosynthesis: Succinyl
Assessment:
Plasma PLP is best indicator.
RDA
1.3
Deficiency
Rare in US. Common in elderly, alcoholics,
individuals on therapy drugs
