KIN 343 - 11.23 Vitamin B6 - Functions
Vitamin B6 Functions: Pyridoxal Phosphate
Main Active Form
Pyridoxal phosphate (PLP) is the active cofactor from vitamin B6 involved in various enzymatic reactions.
It serves as a cofactor for over 100 different enzymes in the human body.
Amino Acid Metabolism
PLP plays a significant role in amino acid metabolism.
Key metabolic pathways include entry of amino acids into the TCA cycle.
Heme Synthesis
First Enzyme in Heme Synthesis
PLP is a cofactor for Delta Aminolevulinic Acid Synthase, the first enzyme in heme synthesis (involved in hemoglobin production).
Vitamin B6 deficiency leads to impaired hemoglobin production, resulting in microcytic (small) and hypochromic (low color) red blood cells.
Symptoms of deficiency include anemia due to lack of hemoglobin.
Niacin Synthesis
Conversion of Tryptophan to Niacin
PLP is involved in the metabolic pathway converting tryptophan to niacin.
60 mg of tryptophan can produce about 1 mg of niacin.
Deficiency in vitamin B6 can impair niacin synthesis, leading to similarities between niacin deficiency symptoms and vitamin B6 deficiency symptoms.
Neurotransmitter Synthesis
Role in Neurotransmitter Production
PLP is essential for synthesizing important neurotransmitters:
Serotonin:
Synthesized from 5-hydroxytryptophan.
Deficiencies are linked to mood disorders, including depression.
Gamma Aminobutyric Acid (GABA):
Produced from glutamate; critical for memory and learning.
Impairment can lead to neurological issues.
Glycogen Degradation
Additional Functions of PLP
Required in glycogen degradation pathways.
Important in the interconversion of amino acids to substrates (e.g., pyruvate) for energy production or gluconeogenesis.
Summary of Key Points
Pyridoxine vs. Pyridoxal
Pyridoxine is the stable form of vitamin B6 found in plants, often confused in literature with pyridoxal.
PLP is critical for various enzymatic reactions, specifically in body metabolism, neurotransmitter synthesis, and energy production.