Define Absorption, Storage and Elimination of Pyridoxine?

Pyridoxine, pyridoxal and pyridoxamine (along with their phosphorylated forms) occur in plant and animal foods. The phospborylated B₆ vitamers are dephosphorylated by membrane bound alkaline phosphatase (found at' the intestinal brush border) and absorption occurs primarily in the intestine (jejunum) by passive diffusion as illustrated in Figure.

After absorption, each form of the vitamin is again phosphorylated (i.e. PLP, PNP, PMP)  and retained. This process is called metabolic trapping. Thus, free vitamers enter by passive diffusion, facilitated by metabolic trapping. The vitamin is transported in blood both in plasma and in red cells, mainly bound to albumin (refer to Figure) in plasma and haemoglobin in erythrocytes. Eighty percent of vitamin B₆ is present in muscle. Excretion is through the urinary pathway.