KIN 343 - 11.17 Vitamin B5 Digestion and Absorption

Coenzyme A is the primary form in which pantothenic acid (Vitamin B5) is available in the diet.
In most foods, pantothenate (the form of Vitamin B5) is attached to Coenzyme A.
To utilize pantothenic acid, Coenzyme A must be hydrolyzed, which occurs through a series of biochemical steps.
This process results in the production of free pantothenic acid, which can then be absorbed.

Pantothenic acid absorption occurs via an active process linked to sodium-potassium ATPase.
The sodium-dependent multivitamin transporter actively transports pantothenic acid into cells by coupling its uptake with sodium transport.
This process utilizes the natural sodium gradient established by ATP expenditure, although ATP is not directly used by the transporter itself.

The sodium-dependent vitamin transporter is present in both the small intestine and large intestine.
The presence of this transporter is crucial as bacteria in the large intestine also synthesize pantothenate, which can be absorbed.
The bacterial synthesis of pantothenic acid occurs during fermentation processes in the colon.
The uptake of synthesized pantothenate is facilitated by the sodium-dependent multivitamin transporter located on enterocytes and colonocytes.

The absorption of pantothenic acid can be regulated by dietary intake.
At the Adequate Intake (AI) levels, about 50% of dietary pantothenate is absorbed.
However, when the intake reaches 10 times the AI, absorption efficiency drops significantly to about 10%.
This indicates a capacity to modulate absorption efficiency in response to varying dietary levels of pantothenic acid.