Pteroylglutamic acid assay

One patient has been found with this deficiency (All). Hie patient, an infant, was mentally retarded, had a megaloblastic anemia and abnormally high levels of serum and erythrocyte folate. In spite of the high serum folate concentration there was a marked rise in the reticulocyte count when the patient was treated with folate. It was thought that the patient had impaired utilization of -methyltetrahydrofolate. Assay of liver W -methyltetrahy-drofolate transferase showed it to be reduced. It was suggested that folate accumulated at the N -methyltetrahydrofolate block and could therefore not be further utilized. Treatment with pteroylglutamic acid provided a means of producing active folate up to the point of the block. Unfortunately this patient was also treated with pyridoxine, and it is not clear which vitamin was responsible for the reticulocyte response. Further studies are required to determine the precise nature of this metabolic disorder. 

Chemical Methods. Assay of these peptides by chemical methods is based upon the following reactions. Pteroylglutamic acid is reduced by metallic zinc in acid solution, and the liberated arylamine is diazotized and coupled with Bratton and Marshall reactant (90). The coupled compound is colored and therefore determined by photometry (305). p-Aminobenzoylpolyglutamic acid is also determined by the same method. 

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