PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “PYRIDOXAL PHOSPHATE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35Linked to original sources
PubMed1980

Transport and metabolism of pyridoxine in rat liver.

Evidence, obtained with in situ perfused rat liver, indicated that pyridoxine is taken up from the perfusate by a non-concentrative process, followed by metabolic trapping. These conclusions were reached on the basis of the fact that at low concentrations (0.125 microM), the 3H of [3H]pyridoxine accumulated against a concentration gradient, but high concentrations (333 microM) of pyridoxine or 4-deoxypyridoxine prevented this apparent concentrative uptake. Under no conditions did the tissue water:perfusate concentration ratio of [3H]pyridoxine exceed unity. The perfused liver rapidly converted the labeled pyridoxine to pyridoxine phosphate, pyridoxal phosphate and pyridoxamine phosphate and released a substantial amount of pyridoxal and some pyridoxal phosphate into the perfusate. Since muscle and erythrocytes failed to oxidize pyridoxine phosphate to pyridoxal phosphate, it is suggested that the liver plays a major role in oxidizing dietary pyridoxine and pyridoxamine as their phosphate esters to supply pyridoxal phosphate which then reaches to other organs chiefly as circulating pyridoxal.

Absorption↗
PubMed1981

Function of the phosphate group of pyridoxal 5'-phosphate in the glycogen phosphorylase reaction.

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 of pyridoxal phosphoglucose was only 1/100 compared with that of pyridoxal phosphate. The enzyme reconstituted with pyridoxal phosphoglucose showed no enzymatic activity at all even after prolonged incubation of the enzyme with substrates and activator. The present data would contradict participation of the phosphate group of pyridoxal phosphate in a covalent glucosyl-enzyme intermediate even if the covalent intermediate was formed during the catalysis.

Animals↗
PubMed1999

A simple, sensitive and reproducible assay for pyridoxal 5'-phosphate and 4-pyridoxic acid in human plasma.

We describe a procedure for the measurement of pyridoxal 5'-phosphate and of 4-pyridoxic acid in human plasma samples. It is based on the conversion of pyridoxal 5'-phosphate to 4-pyridoxic acid 5'-phosphate by cyanide in alkaline medium, followed by a high pressure liquid chromatographic separation, with fluorescence detection at acid pH. The assay is robust, sensitive, linear over a wide range, reproducible, and simple to perform. Samples stored at -80 degrees C are stable. Satisfactory agreement was obtained with results from the tyrosine decarboxylase-based assay for pyridoxal 5'-phosphate, in two other laboratories. Plasma samples from a National Survey of older British people were analyzed, and reference intervals for plasma pyridoxal 5'-phosphate intervals were derived. From the lower 2.5 percentile of the reference group, taken as the lower cut-off of the normal range, ca. 20% of elderly men and 11% of elderly women in the UK showed evidence of biochemical deficiency.

Aged↗
PubMed1983

Modification of pyruvate, phosphate dikinase with pyridoxal 5'-phosphate: evidence for a catalytically critical lysine residue.

Pyruvate, phosphate dikinase from Bacteroides symbiosus is strongly inhibited by low concentrations of pyridoxal 5'-phosphate. The inactivation follows pseudo-first-order kinetics over an inhibitor concentration range of 0.1-2 mM. The inactivation is highly specific since pyridoxine and pyridoxamine 5'-phosphate, analogues of pyridoxal 5'-phosphate, which lack an aldehyde group, caused little or no inhibition even at high concentrations. The unreduced dikinase-pyridoxal 5'-phosphate complex displays an absorption maxima near 420 nm, typical for Schiff base formation. Following reduction of the Schiff base with sodium borohydride, N6-pyridoxyllysine was identified in the acid hydrolysate. When the enzyme was incubated in the presence of pyridoxal 5'-phosphate and reducing agent, the ATP/AMP, Pi/PPi, and pyruvate/phosphoenolpyruvate isotopic exchange reactions were inhibited to approximately the same extent, suggesting that the modification of the lysyl moiety causes changes in the enzyme that affect the reactivity of the pivotal histidyl residue. Phosphorylation of the histidyl group appears to prevent the inhibitor from attacking the lysine residue. On the other hand, addition of pyridoxal 5'-phosphate to the pyrophosphorylated enzyme promotes release of the pyrophosphate and yields the free enzyme which is subject to inhibition.

Bacteroides↗
PubMed2004

Clinical analysis of vitamin B(6): determination of pyridoxal 5'-phosphate and 4-pyridoxic acid in human serum by reversed-phase high-performance liquid chromatography with chlorite postcolumn derivatization.

A reversed-phase high-performance liquid chromatography (HPLC) method with fluorometric detection was developed for the routine determination of pyridoxal 5'-phosphate (PLP) and 4-pyridoxic acid (4-PA) in serum. Chlorite postcolumn derivatization was used to oxidize PLP to a more fluorescent carboxylic acid form. Sensitivity improved fourfold for PLP using chlorite postcolumn derivatization over traditional bisulfite postcolumn derivatization. The HPLC injection cycle was 15 min, facilitating a throughput of 60 patient samples (72 injections that included standards and quality control (QC) samples) in 18.5h. Method precision was evaluated using three serum QC pools with PLP and 4-PA concentrations of 11.5-34.8 nmol/L and 10.4-21.0 nmol/L, respectively. Within-run (n=7) repeatabilities were 0.6-1.2% for PLP and 0.9-1.8% for 4-PA. Run-to-run (n=23) reproducibilities were 3.6-6.7% for PLP and 3.7-5.6% for 4-PA. Relative detection (3sigma(0)) and quantitation (10sigma(0)) limits were 0.3 and 0.9 nmol/L, respectively, for both PLP and 4-PA using a 10-microl sample injection volume. Analytical recoveries ranged from 97 to 102%. Patient-matched serum and plasma specimens (n=25) were analyzed to evaluate specimen-type bias. Of the plasma types evaluated, heparinized plasma introduced the lowest relative bias for PLP (-5.3%) and minimal bias for 4-PA (-2.3%) compared with serum. Ethylenediaminetetraacetic acid (EDTA) plasma showed the lowest bias for 4-PA (0.7%) but a relatively high bias for PLP (13.0%) due to a chromatographic interference. Human serum samples from a non-representative population subset (n=303) were commensurate with values published for other vitamin B(6) HPLC methods. These values gave geometric means of 42.4 nmol/L for PLP and 27.3 nmol/L for 4-PA. Medians for PLP and 4-PA were 40.1 and 21.8 nmol/L, respectively. The high sensitivity, precision, and throughput of this method, combined with its minimal serum specimen (150 microl) and sample injection (10 microl) volume requirements, make it well suited for routine clinical vitamin B(6) analysis.

Calibration↗
PubMed2001

Effect of phosphate on stability of pyridoxal in the presence of lysine.

The stability of the biologically active compound vitamin B(6) in aqueous solution was investigated. Schiff base formation is the major reaction between the epsilon-amino group of lysine and the aldehyde group of both pyridoxal and pyridoxal phosphate. Model systems composed of equal molar concentrations of lysine with either pyridoxal or pyridoxal phosphate were used to study the effect of proton transfer on Schiff base formation. Pyridoxylidenelysine was found to be the major product in both lysine/pyridoxal and lysine/pyridoxal phosphate systems. Quantitation of residual pyridoxal and pyridoxal phosphate was conducted using an HPLC to evaluate the degradation of pyridoxal and pyridoxal phosphate. The results indicate both the free phosphate ion in the buffer system and the bound phosphate on pyridoxal phosphate can enhance the formation of the Schiff base. The phosphate group serves as both proton donor and acceptor, which catalyzes the Schiff base formation. The aldehyde group on pyridoxal phosphate was found to be much more reactive than that on pyridoxal. The bound phosphate group on pyridoxal phosphate, with proton donating and accepting groups in close proximity, can simultaneously donate and accept protons, thus enhancing Schiff base formation between the aldehyde group and the epsilon-amino group. The deterioration rate of pyridoxal phosphate was faster than that of pyridoxal in an aqueous system.

Drug Stability↗