BACKGROUND Homocysteine, a risk factor of cardiovascular disease, cognitive disorders, and pregnancy complications, exists at a point of metabolic convergence of several B vitamins, including vitamins B(6) and B(2) (riboflavin). Measurement of the various forms of these vitamins may be useful for the study of hyperhomocysteinemia as well as for the assessment of vitamin status. METHODS Plasma...

y-Aminobutyric acid is present in the free form in large amounts in brain (l-3), where it is formed from glutamic acid by a L-glutamic acid decarboxylase (2, 4, 5). The enzyme requires pyridoxal phosphate as coenzyme (5), which can be synthesized in brain from adenosinetriphosphate and pyridoxal (6). This decarboxylase has a high degree of substrate and coenzyme specificity (6). The concentrati...

The importing of vitamin B6 by renal proximal tubular cells from the rat is facilitated and Na(+)-dependent and reflects specificity for the meta-phenolate pyridinium structure with a 5-hydroxymethyl function. This transporter can, however, accept competitively each of the natural nonphosphorylated vitamers (pyridoxine, pyridoxamine, and pyridoxal) and other B6 analogues differing only in the g...

The neurocirculatory responses to exercise are exaggerated in hypertension, increasing cardiovascular risk, yet the mechanisms remain incompletely understood. The aim of this study was to examine the in vitro effectiveness of pyridoxal-5-phosphate as a purinergic (P2) receptor antagonist in isolated murine dorsal root ganglia (DRG) neurons and the in vivo contribution of P2 receptors to the neu...

Although pyridoxal, pyridoxamine, and pyridoxine are all known to occur naturally (l), almost no information concerning the distribution of these individual forms of vitamin Bs is available. Use of three microorganisms for the individual detection of these three substances has been previously suggested (1, 2). Since Lactobacillus casei responds only to pyridoxal,’ this substance could be determ...

Streptococcus faecalis 8043 concentrates extracellular [3H]pyridoxal or [3H]pyridoxamine primarily as the corresponding 5'-phosphates. Accumulation of pyridoxamine requires an exogenous energy source and is inhibited by glycolysis inhibitors. A membrane potential is not required for transport of pyridoxamine, and an artificially generated potential does not drive uptake in this organism. Based ...