pyridoxine transport

Definition

Target type: biologicalprocess

The directed movement of pyridoxine into, out of or within a cell, or between cells, by means of some agent such as a transporter or pore. Pyridoxine, 2-methyl-3-hydroxy-4,5-bis(hydroxymethyl)pyridine, is one of the vitamin B6 compounds. Pyridoxal, pyridoxamine and pyridoxine are collectively known as vitamin B6, and are efficiently converted to the biologically active form of vitamin B6, pyridoxal phosphate. [GOC:mah]

Pyridoxine, also known as vitamin B6, is an essential nutrient that plays a crucial role in various metabolic processes within the body. Its transport involves a complex interplay of membrane proteins and carrier molecules that facilitate its absorption, distribution, and utilization. The primary route of pyridoxine intake is through dietary sources, and its absorption primarily occurs in the small intestine. Once ingested, pyridoxine undergoes a series of transformations to form its active coenzyme forms, pyridoxal phosphate (PLP) and pyridoxamine phosphate (PMP). The transport process involves the following key steps:

1. **Absorption:** Pyridoxine is taken up from the intestinal lumen into enterocytes (intestinal cells) through a passive diffusion mechanism. This process is facilitated by the presence of specific membrane transporters, such as the sodium-dependent multivitamin transporter (SMVT). SMVT, a member of the SLC5A6 family, is a high-affinity transporter responsible for the absorption of various water-soluble vitamins, including pyridoxine.

2. **Conversion to Active Forms:** Within the enterocytes, pyridoxine is converted to its active coenzyme forms, PLP and PMP, through a series of enzymatic reactions catalyzed by pyridoxine kinases. These enzymes phosphorylate pyridoxine to form pyridoxal 5'-phosphate (PLP), the most active form of vitamin B6.

3. **Distribution:** PLP and PMP are then transported from the enterocytes into the bloodstream. The mechanism of transport across the intestinal epithelium is not fully understood but is believed to involve both active and passive diffusion. Once in the bloodstream, PLP and PMP are bound to plasma proteins, primarily albumin, for distribution to various tissues throughout the body.

4. **Cellular Uptake:** The active coenzyme forms of pyridoxine, PLP and PMP, are taken up by cells through specific membrane transporters. These transporters, known as pyridoxal phosphate transporters (PLPT), are members of the SLC38 family and are responsible for the active transport of PLP into various cells, including neurons, muscle cells, and erythrocytes.

5. **Metabolic Functions:** Once inside the cell, PLP and PMP participate in a wide range of metabolic reactions, including:
- **Amino acid metabolism:** PLP acts as a coenzyme for numerous enzymes involved in the synthesis, degradation, and transamination of amino acids.
- **Carbohydrate metabolism:** PLP is essential for the conversion of glycogen to glucose.
- **Lipid metabolism:** PLP is involved in the synthesis of sphingolipids, which are important components of cell membranes.
- **Neurotransmitter synthesis:** PLP is required for the synthesis of neurotransmitters, such as dopamine, serotonin, and norepinephrine.

6. **Excretion:** Excess pyridoxine is excreted primarily in the urine, primarily as pyridoxic acid, a metabolic byproduct of PLP.

The transport of pyridoxine is a tightly regulated process that ensures adequate levels of vitamin B6 are available for various metabolic functions. Deficiencies in pyridoxine can lead to various health issues, including anemia, seizures, and neurological disorders. Therefore, it is essential to consume adequate dietary sources of pyridoxine to maintain optimal health.
'"

Proteins (1)

Compounds (1)