Saccharopine dehydrogenase (EC 1.5.1.7) from bakers’ yeast was reversibly inactivated by pyridoxal and pyridoxal 5’-phosphate. The inactivation by pyridoxal 5’-phosphate was accompanied by the appearance of a peak at 428 nm, which was shifted to 325 nm upon reduction with NaBH4. Paper chromatography of an acid hydrolysate of the pyridoxal 5’-phosphate-treated, NaBH4-reduced enzyme showed the pr...

To understand the catalytic mechanism of glycogen phosphorylase (EC 2.4.1.1), pyridoxal(5')phospho(1)-beta-D-glucose was synthesized and examined as a hypothetical intermediate in the catalysis. Pyridoxal phosphoglucose bound stoichiometrically to the cofactor site of rabbit muscle phosphorylase b in a similar mode of binding to the natural cofactor, pyridoxal 5'-phosphate. The rate of binding ...

The stimulation of the carboxylase reaction by effectors of ribulose 1,5-bisphosphate carboxylase/oxygenase displays higher sensitivity towards pyridoxal 5'-pyridoxal 5'-phosphate inhibition than the catalytical process itself. Pyridoxal 5'-phosphate binding to the enzyme is not affected by the modulators 6-phosphogluconate and fructose 1,6-bisphosphate at low concentrations at which these agen...

Using purified enzymes of human origin and patients' sera, we examined factors influencing the in vitro association of pyridoxal phosphate with aspartate aminotransferase (EC 2.6.1.1). The rate of association was markedly retarded by phosphate buffer in comparison with tris(hydroxymethyl)aminomethane or six other buffers. Pyridoxal phosphate at an incubation concentration of 130 mumol/liter rea...

The r&e of vitamin Bg in amino acid metabolism has been well established through enzyme studies (l-3) and by the substitution for various amino acids in growth studies (4-6). The coenzyme form, synthetic pyridoxal phosphate (7), functions as the coenzyme for amino acid decarboxylases (S-10), transaminases (2, 3), tryptophan formation (11)) and tryptophan breakdown by tryptophanase (12). The rea...

The concentrations of pyridoxal 5'-phosphate, and the holoenzyme activities and apoenzyme contents of alanine aminotransferase and aspartate aminotransferase in plasma were determined simultaneously in healthy individuals, patients with renal insufficiency with and without chronic haemodialysis and in patients with acute myocardial infarction. Plasma pyridoxal 5'-phosphate is significantly dimi...

Commercial control sera contain varying amounts of pyridoxal-5'-phosphate. Normalization of aminotransferase activity measurement with enzyme "standards" is possible only when pyridoxal-5'-phosphate is added to the reaction medium. Pyridoxal-5'-phosphate addition should be compulsory in national recommendations.

Yeast tRNAPhe, Yeast tRNATyr, Pyridoxal-5'-phosphate Yeast tRNAPhe and tRNATyr were reacted with the fluo­ rescent reagent pyridoxal-5'-phosphate and the modified tRNAs were analysed with respect to the number and posi­ tion of modified nucleosides and with respect to aminoacylation. a) Following the intrinsic fluorescence of pyridoxal-5'phosphate, the treatment of tRNATyr with increasing amoun...

Lathyrogens decrease collagen and elastin cross-linking by inhibiting lysine oxidase. The lathyrogens isoniazid and semicarbazide decrease liver pyridoxal phosphate and are teratogenic; all their effects are reversed by pyridoxal. beta-Aminopropionitrile, another lathyrogen, does not affect liver pyridoxal phosphate, and its lathyrogenic and teratogenic effects are not reversed by pyridoxal. Ti...

Tritium-labeled pyridoxamine, pyridoxal S/-phosphate, and pyridoxine 5’-phosphate were prepared and administered intravenously to mice, and the distribution of isotope in liver and carcass between pyridoxine, pyridoxine 5’-phosphate, pyridoxal, pyridoxal S/-phosphate, pyridoxamine, and pyridoxamine 5’-phosphate was determined at different times after administration. The vitamin B6 forms were ex...