Human pyridoxal phosphatase. Molecular cloning, functional expression, and tissue distribution

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Pyridoxal phosphatase (PLP phosphatase) dephosphorylates pyridoxal 5'-phosphate (PLP) and pyridoxine 5'-phosphate.
• Vitamin B6 metabolism is essential for numerous physiological processes.
• Understanding PLP phosphatase is key to elucidating vitamin B6 pathways.

Purpose of the Study:

• To identify and characterize the human PLP phosphatase.
• To investigate the molecular properties and expression of human PLP phosphatase.
• To explore the enzyme's role in vitamin B6 metabolism.

Main Methods:

• Human brain cDNA cloning and sequencing.
• Gene mapping to human chromosome 22q12.3.
• Isolation and characterization of mouse PLP phosphatase.
• Recombinant expression in E. coli.
• Enzyme kinetics (Km, kcat) determination.
• Tissue-specific mRNA expression analysis.

Main Results:

• A human cDNA predicted a 296-amino acid protein (31,698 Da) for PLP phosphatase, encoded by two exons on chromosome 22q12.3.
• Human and mouse PLP phosphatases share 93% sequence identity, with homologs found across various organisms.
• Recombinant human PLP phosphatase exhibited kinetic properties similar to the erythrocyte enzyme (Km=2.5 µM, kcat=1.52 s⁻¹ for pyridoxal).
• Human PLP phosphatase mRNA is highly abundant in the brain and expressed in a tissue-specific manner.

Conclusions:

• The molecular characterization of human PLP phosphatase provides a foundation for further research.
• The enzyme's high abundance in the brain suggests a significant role in neurological vitamin B6 metabolism.
• Further investigation into PLP phosphatase may offer new insights into vitamin B6 metabolic pathways.