Pyridoxal(5')diphospho(1)-alpha-D-glucose was used to reconstitute glycogen phosphorylase beta (1,4-alpha-D-glucan:orthophosphate alpha-D-glucosyltransferase, EC 2.4.1.1) from rabbit muscle, replacing the natural pyridoxal 5'-phosphate coenzyme. Incubation of the reconstituted enzyme alone resulted in the gradual cleavage of the synthetic cofactor to pyridoxal 5'-phosphate, which caused slow re...

The classical studies of Rabinowitz and Snell (1) demonstrated that vitamin Be exists in at least three forms in the tissues of animals and plants: pyridoxine, pyridoxamine, and pyridoxal. Their assay procedure, a differential growth response of microorganisms to pyridoxine, pyridoxamine, and pyridoxal, would not differentiate between the phosphorylated and the nonphosphorylated forms of the vi...

Pyridoxal 5’.phosphate labeled to the extent of 90%’ with 13C in the 4’ (aldehyde) and 5’ (methylene) positions has been synthesized. 13C NMR spectra of this material and of natural abundance pyridoxal 5’.phosphate are reported, as well as r3C NMR spectra of the Schiff base formed by reaction of pyridoxal 5’.phosphate with n-butylamine, the secondary amine formed by reduction of this Schiff bas...

The pyridoxal phosphate reactivation of the apo form of aspartate aminotransferase (EC 2.6.1.1) in human serum has been studied with "normal" and above-normal activity of this enzyme. The extent of the reactionation did not depend on the presence of the substrates, L-aspartate or 2-oxoglutarate. Reactivation was greatest with 110 mumol of added pyridoxal phsophate present per liter during a pre...

The gene (pykA) encoding pyridoxal kinase which converts pyridoxal (vitamin B(6)) to pyridoxal phosphate was isolated from Dictyostelium discoideum using insertional mutagenesis. Cells of a pykA gene knockout grew poorly in axenic medium with low yield but growth was restored by the addition of pyridoxal phosphate. Sequencing indicated a gene, with one intron, encoding a predicted protein of 30...

[3H]Pyridoxamine was orally administered to mice in physiological amounts, and the distribution of isotope between the six recognized forms of vitamin B6 and pyridoxic acid was determined at different times in the intestine, liver, blood, and brain. After 7 min about 50% of the radioactivity in pyridoxamine had been absorbed by the intestine and transported to the blood and other organs. Labele...

1. Pyridoxal 5'-phosphate is a cofactor essential for the enzymic activity of aminolaevulinate synthetase from Rhodopseudomonas spheroides. It also aids activation of the low-activity enzyme by trisulphides such as cystine trisulphide, whereas inactivation of enzyme is facilitated by its absence. 2. The fluorescence spectrum of purified high-activity enzyme is that expected for a pyridoxal phos...

(1) showed that pyridoxal-5'-phosphate (a phos-phorylated derivative of vitamin B6) is essential for serum aspartate trans-aminase (AST) activity.This coen-zyme is bound to an amino group of the enzyme during transfer,becoming pyridoxamine phosphate (2). In 1954, Karmen et al. (3) described a practical method of measuring AST activity. Although they gave no data, they did add buffered pyridoxal...

1. The effect of pyridoxal 5'-phosphate on the activity of ox liver glutamate dehydrogenase towards different amino acid substrates was investigated. 2. Both alanine and glutamate activities decreased steadily in the presence of pyridoxal 5'phosphate. 3. The alanine/glutamate activity ratio increased as a function of inactivation by pyridoxal 5'-phosphate, indicating that glutamate activity is ...