Pyridoxine, pyridoxal, pyridoxamine, pyridoxal phosphate (PLP)
Adequate Intake ?:
Variety of reactions for nutrient metabolism and energy production; gene expression. Dermititis, cheilosis, glossitis, angular stomatitis, nervous system dysfunction. Major Food Sources: Beef, fish, legumes, potato, banana, whole grains. RDA: 1.3 mg
Pyridoxine = Pyridoxal = Transamination (TRANSfering an amino group (NH2) to a keto acid), deamination, decarboxylation , glycogen degradation, transelenation
History & Discovery:
In 1933, Kuhn isolated lactoflavin from milk and described the structure of riboflavin for the first time.
In 1938, Kuhn and Szent-Gyorgyi, who a Hungarian professor in biochemistry, isolated Vitamin B6 using photo-spectrometry and the use of reducing agents.
PN, PNP most common forms in plant foods
PL, PLP, PM, PMP most common forms in animal foods and our bodies
Most adults in the US consume 1.5-2 mg/day of Vitamin B6
Jejunum is the Primary Site of Absorption.
Phosphorylated vitamers must be dephosphorylated through alkaline phosphatase, a zinc-dependent enzyme.
Passive diffusion of PL, PM, PL through passive diffusion in jejunum and ileum.
Absorption and Storage:
Blood: 75-90% PL and PLP (animal forms)
Muscle: Main storage site - 75-80% mostly as PLP -> inside the cell stored as PLP, cannot escape the cell and act as a cofactor.
Vitamin B6 exists as 6 vitamers.
Pyridoxine (PN) -
Pyridoxal (PL) -
Pyridoxamine (PM) -
Pyridoxine phosphate (PNP)
Pyridoxal phosphate (PLP)
Pyridoxamine phosphate (PMP)
Decarboxylation reactions involve the removal of the carboxy (COO2) group from an amino acid or other compound. Many of these reactions are involved in the production of neurotransmitters for nervous system function.
Histidine -> Decarboxylase -> Histimine + CO2 "Chemical Messenger"
Tyrosine -> L-Dopa -> Decarboxylase -> Dopamine
Deamination - remove amino group from amino acids, typically so the molecule can be used for energy production. This requires PLP.
Plays a role in transelenation - selenoproteins play a role in anti-oxidant processes in our body.
Heme synthesis uses B6 to process glycine and succinyl-CoA
Serine hydroxymethyltransferase is a PLP-dependent enzyme involved in folate metabolism.
Deficiency Diseases, Detection, Cures:
Cheilosis and/or glossitis
Changes in reflexes
Nervous system - general effects