. The Biochemistry of B vitamins. Vitamins; Vitamin B complex. H3C pyridoxal phosphate pyridoxamine phosphate Assay Methods. The method generally favored for the enzymatic determination of pyridoxal phosphate is the system in which tyrosine apodecarboxylase is reactivated. The source of apoenzyme is a dried cell powder prepared from Streptococcus faecalis R., which has been grown on an alanine-rich, vitamin B6-deficient medium. A detailed description of the assay procedure has been The powder is easily pre- pared and is stable over long periods of time. When preparations are assa
. The Biochemistry of B vitamins. Vitamins; Vitamin B complex. H3C pyridoxal phosphate pyridoxamine phosphate Assay Methods. The method generally favored for the enzymatic determination of pyridoxal phosphate is the system in which tyrosine apodecarboxylase is reactivated. The source of apoenzyme is a dried cell powder prepared from Streptococcus faecalis R., which has been grown on an alanine-rich, vitamin B6-deficient medium. A detailed description of the assay procedure has been The powder is easily pre- pared and is stable over long periods of time. When preparations are assayed with the powder and a substrate, the rate of carbon dioxide evolution is a measure of the amount of pyridoxal phosphate in the preparations. More elaborate procedures are needed to prepare the apo- enzymes of decarboxylases, transaminases, and tryptophanases from normal cells or tissues; this makes their use as testing agents less con- venient than the procedure employing deficient cells. A microorganism which responds only to the phosphorylated deriva- tives of either pyridoxal or pyridoxamine has been The amine phosphate is three to five times as active as the aldehyde ester. The individual determination of each of the unphosphorylated com- ponents of the B6 group—pyridoxine, pyridoxal, and pyridoxamine— can be accomplished by a differential method in which samples are analyzed by use of three organisms which respond differently to the three If materials are tested by such a procedure both before and after dilute acid hydrolysis (which cleaves the phosphate ester linkage), it is possible to get a reasonably accurate estimate of both the pyridoxal phosphate and the pyridoxamine phosphate contents of crude The ease with which the amine and aldehyde forms can be interconverted, by nonenzymatic as well as enzymatic reactions, should always be considered when interpreting results obtained by this method. The formation of the amine
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