PDXP Human

Pyridoxal phosphatase is an enzyme that plays a crucial role in the metabolism of vitamin B6. It is responsible for the dephosphorylation of pyridoxal 5’-phosphate (PLP) to pyridoxal, which is a vital step in the vitamin B6 metabolic pathway. This enzyme belongs to the family of hydrolases, specifically those acting on phosphoric monoester bonds .

The systematic name of pyridoxal phosphatase is pyridoxal-5’-phosphate phosphohydrolase. It is also known by several other names, including vitamin B6 (pyridoxine) phosphatase, PLP phosphatase, and PNP phosphatase . The enzyme catalyzes the reaction:

$$\text{pyridoxal 5'-phosphate + H}_2\text{O} \rightarrow \text{pyridoxal + phosphate}$$

Human pyridoxal phosphatase has been successfully cloned and expressed in various systems. The cDNA encoding this enzyme predicts a protein of 296 amino acids with a molecular weight of approximately 31,698 Da . The gene encoding pyridoxal phosphatase is located on human chromosome 22q12.3 and consists of two exons .

Recombinant pyridoxal phosphatase has been expressed in Escherichia coli, and its characteristics have been studied extensively. The recombinant enzyme displays kinetic parameters similar to those of the native enzyme found in human erythrocytes. Specifically, the enzyme has a Km value for pyridoxal of 2.5 µM and a kcat value of 1.52 s^-1 .

The expression of pyridoxal phosphatase is tissue-specific. It is highly abundant in the brain, but it is also expressed in other tissues such as the liver and testis . This differential expression suggests that the enzyme may have specialized functions in different tissues.

As of late 2007, several structures of pyridoxal phosphatase have been solved, providing insights into its catalytic mechanism and substrate specificity. These structural studies have been instrumental in understanding how the enzyme interacts with its substrates and how it is regulated .