In addition to its role in bone mineralization, alkaline phosphatase (ALP) dephosphorylates pyridoxal 5’-phosphate (PLP, or vitamin B6) into pyridoxal (PL), allowing it to cross the plasma membrane into the central nervous system (CNS). Within the CNS, PL is rephosphorylated into PLP. Intracellular PLP is involved in neurotransmitter synthesis (eg, gamma aminobutyric acid [GABA], dopamine, serotonin).2,6
In patients with hypophosphatasia, PLP deficiency in the CNS can cause fatal vitamin B6–responsive seizures2,7,8