Pyridoxal phosphate can act as a specific photosensitizer for amino acid residues in rabbit muscle and spinach leaf aldolases, but the residues affected depend on the pH of the reaction. Below pH 8 one histidine residue per enzyme subunit is destroyed; above pH 8.5 there is little loss of histidine, and photoinactivation is associated with the destruction of specific tyrosine residues, particul...

1. Pig heart mitochondrial malate dehydrogenase incubated with pyridoxal 5'-phosphate at pH 8.0 and 25 degrees C gradually loses activity. Such inactivation can be largely reversed by dialysis or by addition of L-lysine or L-cysteine, and can be made permanent by NaBH4 reduction. 2. Modification of malate dehydrogenase with pyridoxal 5'-phosphate at 35 degrees C involves two phases, an initial ...

of pyridoxal 5 -phosphate. Biochim Biophys Acta 1973;304:765–73. 13. Dalton K, Dalton MT. Characteristics of pyridoxine overdose neuropathy syndromes. Acta Neurol Scand 1987;76:8–11. 14. Ubbink JB, Serfontein WJ, De Villiers LS. Stability of pyridoxal 5 -phosphate semicarbazone: applications in plasma vitamin B6 analysis and population surveys of vitamin B6 nutritional status. J Chromatogr B Bi...

Rats with vitamin B6 deficiency excrete cystathionine in the urine (Hope, 1957). Cystathionine is an amino acid in the pathway of synthesis of cysteine from methionine (Fig. 1). A methyl group is removed from methionine to produce homocysteine, which condenses with serine to yield cystathionine. This condensation is catalysed by a transulphurase enzyme requiring pyridoxal phosphate as a co-enzy...

There are 16 epsilon-amino groups of lysyl residues which are essential for the activity of ribulose-1,5-bisphosphate carboxylase/oxygenase. These lysyl residues formed a Schiff base with pyridoxal 5'-phosphate which was stabilized by NaBH4 reduction. The stoichiometry of covalently bound pyridoxal 5'-phosphate after NaBH4 reduction was determined spectrophotometrically with a derived molar ext...

on pyridoxine or pyridoxamine as a sole source of carbon and nitrogen (1, 2). This transaminase contains no pyridoxal phosphate, and hence provides a simpler system for mechanistic studies than do the more complex, pyridoxal phosphate-containing transaminases. The enzyme binds pyridoxamine and pyridoxal with almost equal avidity; the latter is bound in part by an azomethine Iinkage to the e-ami...

A procedure is described for obtaining crystalline o-serine dehydrase from a mutant of Escherichia coli which produces this enzyme constitutively. The enzyme appears pure by ultracentrifugal and electrophoretic criteria. In sucrose gradients, serine dehydrase sediments to the same position as horseradish peroxidase, indicating a molecular weight of about 40,000. This corresponds closely to its ...

L-Alanine:glyoxylate aminotransferase was isolated from human liver and purified 900-fold. Pyridoxal phosphate was required for catalytic activity and enhanced the stability of the enzyme during purification and storage. The enzyme underwent activation when heated for 10 min in 10 PM pyridoxal phosphate. Activation resulted in the formation of a nondialyzable pyridoxal phosphate complex with th...

Treatment of 1 microM wheat-germ aspartate transcarbamoylase with 1 mM-pyridoxal 5'-phosphate caused a rapid loss of activity, concomitant with the formation of a Schiff base. Complete loss of activity occurred within 10 min when the Schiff base was reduced with a 100-fold excess of NaBH4. Concomitantly, one amino group per chain was modified. No further residues were modified in the ensuing 30...

The coenzyme function of pyridoxal-phosphate in cysteine desulfhydration and in the mechanistically similar serine and threonine dehydration (deamination) processes has been a subject of discussion in a number of recent publications (see, for example, Snell, 1952, and Braunstein and Shemyakin, 1953). A chemical model reaction has been proposed (Metzler and Snell, 1952). Evidence for pyridoxal-p...