Microassay of Pyridoxal Phosphate Using Tyrosine Apodecarboxylase

  • Lawrence Lumeng
  • Alec Lui
  • Ting-Kai Li


Pyridoxal 5′-phosphate (PLP) assay based on the coenzyme-dependent decarboxylation of L-tyrosine by tyrosine apodecarboxylase (EC was the first enzymatic method developed in vitamin B-6 analysis. Originally isolated from Streptococcus faecalis and partially purified by Epps (1) in 1944, this apoenzyme was subsequently used by Umbreit et al. (2) and Baddiley and Gale (3) to identify the coenzyme role of PLP in decarboxylation reactions. In these early studies, manometry was employed to follow the generation of CO2 as a function of PLP and sensitivity was low. Although sensitivity was later improved by making certain rearrangements and mechanical changes in the assay system (4,5), it was still insufficient to detect PLP concentrations below 10 ng/ml of plasma.


Blood Plasma Supernatant Fraction Sodium Citrate Buffer Pyridoxal Phosphate Tyrosine Decarboxylase 
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Copyright information

© Springer Science+Business Media New York 1981

Authors and Affiliations

  • Lawrence Lumeng
    • 1
  • Alec Lui
    • 1
  • Ting-Kai Li
    • 1
  1. 1.VA Medical Center and Departments of Medicine and BiochemistryIndiana University School of MedicineIndianapolisUSA

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