Effect Of Pyridoxal Phosphate Research Articles

The effects of pyridoxal phosphate on rabbit liver and kidney fructose 1,6-diphosphatases

Rabbit liver and kidney fructose 1,6-diphosphatases (FDPases) rapidly become desensitized to inhibition by AMP and are partially inactivated when treated with pyridoxal 5′-phosphate. Pyridoxal is somewhat less active than pyridoxal 5′-phosphate and pyridoxamine is inactive. Inactivation and desensitization are reversed by dilution. AMP protects both enzymes against desensitization. It also protects the liver enzyme against loss of catalytic activity, but not the kidney enzyme, which is more sensitive. Pyridoxal 5′-phosphate reacts with approximately 8 ϵ-amino lysine groups in liver FDPase, but the extent of desensitization is complete after incorporation of 4–5 equivalents. The amount of pyridoxal 5′-phosphate that is incorporated is increased when AMP is present. With kidney FDPase, approximately 11 equivalents of pyridoxal 5′-phosphate are incorporated, and this number is not increased by the presence of AMP. The product of the reaction with pyridoxal phosphate was characterized by spectral studies and N 6-pyridoxyllysine was isolated from hydrolyzates of pyridoxal 5′-phosphate-enzyme complexes that had been reduced with sodium borohydride. In addition to differences in their reactions with PLP, rabbit liver and kidney FDPases differ significantly in amino acid composition. However, they appear to be similar in molecular weight and subunit structure.

The effect of pyridoxal phosphate on rabbit muscle aldolase

Rabbit muscle aldolase loses activity when exposed to low concentrations of pyridoxal 5′-phosphate. The inactivation is specifically prevented by substrates and substrate analogues, and is reversed by dilution, or by addition of amino thiols. Pyridoxal 5′-phosphate reacts with approximately six ϵ-amino lysine groups in the enzyme. The product was identified by spectral studies and by reduction with NaBH 4 followed by hydrolysis and isolation of N 6-pyridoxyllysine. Peptides containing N 6-pyridoxyllysine were obtained after cyanogen bromide cleavage of the reduced complex, and the lysine residues that reacted with PLP were shown to be distinct from those involved in Schiff base formation with the substrate. The evidence suggests that pyridoxal 5′-phosphate reacts at one of the phosphate-binding sites of rabbit muscle aldolase. Most of the bound pyridoxal phosphate was located in the amino-terminal peptide, which contained one equivalent of pyridoxyl-P per subunit. Smaller quantities, about one-half equivalent per subunit, were incorporated into the carboxyl-terminal peptide. The lysine residue that forms the Schiff base with dihydroxyacetone phosphate was present in a third peptide located near the center of the chain.

An effect of pyridoxal phosphate on the experimental liver injury by thioacetamide

An effect of pyridoxal phosphate on the experimental liver injury by thioacetamide

A specific interaction of pyridoxal 5′-phosphate and 6-phosphogluconic dehydrogenase

The enzymic activity of crystalline 6-phosphogluconic dehydrogenase from Candida utilis is inhibited by incubation at neutral pH with very low concentrations of pyridoxal 5′-phosphate. No inactivation is observed when the enzyme is incubated with pyridoxal itself, or with pyridoxine or pyridoxamine phosphate. The inhibition is reversed by addition of 6-phosphogluconate, by dilution or dialysis, or upon addition of amino acids. The effect of pyridoxal phosphate is competitive with 6-phosphogluconate. The inhibition of the enzymic activity is due to the formation of a Schiff base between the aldehydric group of the inhibitor and the ϵ-amino group of a single lysine residue at the active center of the enzyme. This was established by reduction with sodium borohydride and the isolation of N 6-pyridoxyllysine from acid hydrolyzates. Pyridoxal also forms a Schiff base derivative with the enzyme, but in this case both the Schiff base and the reduced complex are enzymically active. The presence of a phosphate group appears to be important in directing the inhibitor to the particular sensitive lysine residue at the active center of the enzyme.

THE EFFECT OF PYRIDOXAL PHOSPHATE ON SGO-T ACTIVITY IN MYOCARDIAL INFARCTION.

In order to investigate the mechanism that high SGO-T level caused by acute myocardial infarction return to the normal level, the influence of the co-enzyme, pyridoxal phosphate (PAL-P), on SGO-T activity was studied. The changes of SGO-T activity with the addition of PAL-P in the cases with elevated SGO-T level produced experimentally was entirely different from that in the normal. In all of the former cases, a marked increase of SGO-T activity with the addition of PAL-P was recognized. In two clinical cases of acute posterior infarction, an increase of SGO-T activity to abnormal level was observed when PAL-P was added to the serum samples taken in the early stage of myocardial infarction. Therefore, measurement of the increase of SGO-T activity by adding PAL-P was considered to be useful for unveiling minimal discharge of GO-T into the blood.

Effect of Pyridoxal-5′-Phosphate Upon the Histochemical Reaction for Phosphorylase in Tissue Sections

Pyridoxal phosphate decreased in intensity of the histochemical reaction for phosphorylase in tissue sections. It was difficult to prove histochemically that a combination of pyridoxal phosphate with apophosphorylase might be demonstrated through the phosphorylase reaction. It was assumed that the effect of pyridoxal phosphate upon apophosphorylase and upon phosphorylase itself is different respectively.

Effect of pyridoxal 5-phosphate in the presende of vanadyl ions on the de-iodination of thyroxine.

IN the course of a recent investigation of the effects of metal ions on the de-iodination of thyroxine, it was suggested that sulphydryl groups are involved in the regulatory mechanism of de-iodination on the cellular level1,2.

Effects of pyridoxal phosphate on blood coagulation and fibrinolytic system.

Effects of pyridoxal phosphate on blood coagulation and fibrinolytic system.

Effects of pyridoxal phosphate and serine in conversion of indole glycerol phosphate to indole by extracts from tryptophan mutants of [formula omitted][formula omitted

Effects of pyridoxal phosphate and serine in conversion of indole glycerol phosphate to indole by extracts from tryptophan mutants of [formula omitted][formula omitted

The effect of pyridoxal phosphate and its inhibition by carnosine on the ATPase activity and syneresis of myofibrils

Pyridoxal phosphate inhibits the adenosinetriphosphatase activity of myofibrils. The inhibition is greatest at the optimal adenosine triphosphate (ATP) level. The inhibition does not depend on Mg ++ concentration and increases with increasing pH. Carnosine antagonizes the inhibition. The ATP-induced syneresis of myofibrils is likewise inhibited by pyridoxal phosphate, and this effect, too, is reversed by carnosine. The bearing of the results on the relaxing factor system of muscle has been discussed.