New rapid determination of pyridoxal phosphate using tyrosine phenol-lyase.

A rapid, specific, and precise spectrophotometric assay for the determination of pyridoxal phosphate is described. The assay allows for the determination of the cofactor between 0.1 and 1.0 microgram/ml. Its applicability to pyridoxal phosphate in biological fluids was demonstrated by a determination of the plasma half-life in BDF1 mice. Pyridoxal phosphate is absorbed rapidly from the peritoneal cavity and cleared from the plasma with a half-life of about 15 min.