• BMB Reports
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• v.55 no.9
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• pp.439-446
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• 2022

Pyridoxal 5'-phosphate (PLP)-dependent enzymes are ubiquitous, catalyzing various biochemical reactions of approximately 4% of all classified enzymatic activities. They transform amines and amino acids into important metabolites or signaling molecules and are important drug targets in many diseases. In the crystal structures of PLP-dependent enzymes, organic cofactor PLP showed diverse conformations depending on the catalytic step. The conformational change of PLP is essential in the catalytic mechanism. In the study, we review the sophisticated catalytic mechanism of PLP, especially in transaldimination reactions. Most drugs targeting PLP-dependent enzymes make a covalent bond to PLP with the transaldimination reaction. A detailed understanding of organic cofactor PLP will help develop a new drug against PLP-dependent enzymes.

• Nutritional Sciences
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• v.3 no.1
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• pp.31-35
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• 2000

The purpose of this study was to compare the changes in PLP concentrations induced by regular, moderate, and abrupt, high-intensity exercise in the plasma and tissues of vitamin B6 deficient and normal rats. Forty-eight rats were fed either a vitamin B6 deficient (-B6) diet or a normal (+B6) diet for 5 weeks and were subdivided into 4 groups:non-exercise(NE) group: regular, moderate-intensity exercise (RME) group; abrupt, high-intensity exercise (AIE) group; abrupt, high-intensity exercise and recuperation(IRE) group. The RME group was exercised on treadmill ($10^{\circ}$, 0.5-0.8km/h) for 2 hours just before sacrifice at the end of 5th week on the diet and the IER group was recuperated for three days on the diet after being exercised like the AIE group. Pyridoxal 5 -phosphate(PLP) levels were compared in the plasma, liver and skeletal muscle of the rats. Plasma PLP concentration tended to decrease in -B6 rats and tended to increase in +B6 rats with AIE. Plasma PLP concentration in both +B6 rats with AIE and no change in both -B6 and +B6 rats with RME. Muscle PLP concentration decreased in +B6 rats, showed no change in -B6 rats with AIE. Muscle PLP concentrations in both +B6 and -B6 rats did not change with RME. Plasma PLP, liver PLP and muscle PLP concentration of IER returned to those of NE in both +B6 and -B6 rats. These results suggest that changes in PLP concentration in plasma, liver and muscle occur with exercise and are affected by exercise intensity and vitamin B6 status. These changes may be due to interorgan redistribution of PLP.

• Journal of Nutrition and Health
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• v.28 no.5
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• pp.426-434
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• 1995

The purpose of this study were to investigate the effect of fasting and vitamin B6 repletion on tissue concentration of pyridoxal 5-phosphate and urinary excreteion of 4-pyridoxic acid in vitamin B6 deficient rats. Sixty six rats(6 per group) were fed either a vitamin B6 deficient diet (-B6) or a control diet (+B6) for 6 weeks and then rats were repleted with +B6 diet for 2 weeks. Rats were fasted for 1 and 3 days and for 3 days after repletion. Pyridoxal 5-phosphate (PLP) concentration in plasma, liver, skeletal muscle, and heart muscle and urinary 4-pyridoxic acid (4-PA) excretion were compared. Fasting resulted in a significant increase in PLP concentration in the plasma, liver and heart muscle of rats fed the -B6 diet. Skeletal muscle PLP concentration was significantly decreased in +B6 rats but not in -B6 rats. Following vitamin B6 repletion, PLP concentration in the plasma, liver and heart muscle in previously -B6 rats was similar to the respective concentration in +B6 rats while PLP concentration in the skeletal muscle of previously -B6 rats increased, but it was not reached to that of +B6 rats. At day 1 and 2 of the fast, urinary 4-PT excretion increased in both +B6 and -B6 rats although there was no supply of vitamin B6 due to fasting. These results suggest that vitami B6 is redistributed as PLP when there is a caloric deficit and PLP is supplied by an endogenous source, possibly PLP bound to skeletal muscle glycogen phosphorylase.

• BMB Reports
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• v.41 no.5
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• pp.408-413
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• 2008

Pyridoxal-5'-phosphate phosphatase (PLPP) catalyzes the dephosphorylation of pyridoxal-5'-phosphate (PLP). A human brain PLPP gene was fused with a PEP-1 peptide and produced a genetic in-frame PEP-1-PLPP fusion protein. The purified PEP-1-PLPP fusion protein was efficiently transduced into PC12 cells in a time- and dose-dependent manner when added exogenously to culture media. Once inside the cells, the transduced PEP-1-PLPP fusion protein was stable for 36 h. The concentration of PLP was markedly decreased by the addition of exogenous PEP-1-PLPP to media pretreated with the vitamin $B_6$ precursors; pyridoxine, pyridoxal kinase and pyridoxine-5'-phosphate oxidase into cells. The results suggest that the transduction of the PEP-1-PLPP fusion protein can be one mode of PLP level regulation, and to replenish this enzyme in the various neurological disorders related to vitamin $B_6$.

• Journal of Microbiology and Biotechnology
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• v.9 no.6
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• pp.695-703
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• 1999

We have studied the stereospecificities of various pyridoxal 5'-phosphate (PLP) dependent enzymes for the hydrogen transfer between the C-4' of a bound coenzyme and the C-2 of a substrate in the transamination catalyzed by the enzymes. Stereospecificities reflect the structures of enzyme active-sites, in particular the geometrical relationship between the coenzyme-substrate Schiff base and the active site base participating in an $\alpha$-hydrogen abstraction. The PLP enzymes studied so far catalyze only a si-face specific (pro-S) hydrogen transfer. This stereochemical finding suggests that the PLP enzymes have the same topological active-site structures, and that the PLP enzymes have evolved divergently from a common ancestral protein. However, we found that o-amino acid aminotransferase, branched chain L-amino acid aminotransferase, and 4-amino-4-deoxychorismate lyase, which have significant sequence homology with one another, catalyze a re-face specific (pro-R) hydrogen transfer. We also showed that PLP-dependent amino acid racemases, which have no sequence homology with any aminotransferases, catalyze a non-stereospecific hydrogen transfer: the hydrogen transfer occurs on both faces of the planar intermediate. Crystallographical studies have shown that the catalytic base is situated on the re-face of the C-4' of the bound coenzyme in o-amino acid aminotransferase and branched chain L-amino acid aminotransferase, whereas the catalytic base is situated on the si-face in other aminotransferases (such as L-aspartate aminotransferase) catalyzing the si-face hydrogen transfer. Thus, we have clarified the stereospecificities of PLP enzymes in relation with the primary structures and three-dimensional structures of the enzymes. The characteristic stereospecificities of these enzymes for the hydrogen transfer suggest the convergent evolution of PLP enzymes.

• BMB Reports
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• v.29 no.4
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• pp.321-326
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• 1996

Spinach glycolate oxidase was subjected to a series of chemical modifications aimed at identifying amino acid residues essential for catalytic activity. The oxidase was reversibly inactivated by treatment with pyridoxal 5'-phosphate (PLP). The inactivation by PLP was accompanied by the appearance of an absorption peak of around 430 nm, which was shifted to 325 nm upon reduction with $NaBH_4$. After reduction, the PLP-treated oxidase showed a fluorescence spectrum with a maximum of around 395 nm by exciting at 325 nm. The substrate-competitive inhibitors oxalate and oxaloacetate provided protection against inactivation of the oxidase by PLP. These results suggest that PLP inactivates the enzyme by fonning a Schiff base with lysyl residue(s) at an active site of the oxidase. The enzyme was also inactivated by tryptophan-specific reagent N-bromosuccinimide (NBS). However, competitive inhibitors oxalate and oxaloacetate could not protect the oxidase significantly against inactivation of the enzyme by NBS. The results implicate that the inactivation of the oxidase by NBS is not directly related to modification of the tryptophanyl residue at an active site of the enzyme. Treatments of the oxidase with cysteine-specific reagents iodoacetate, silver nitrate, and 5,5'-dithiobis-2-nitrobenzoic acid did not affect significantly the activity of the enzyme.

• Nutritional Sciences
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• v.5 no.1
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• pp.20-25
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• 2002

The vitamin $B_{6}$ status of 49 healthy college student (women, aged 20-26 y) was estimated for evaluation of vitamin $B_{6}$ status and the Korean Recommended Dietary Allowance (RDA) for vitamin $B_{6}$. The average daily vitamin $B_{6}$ intake of the subjects was 0.86 $\pm$ 0.289 mg/d or 61.43 $\pm$ 24.10% of Korean RDA. The average ratio of vitamin $B_{6}$ intake to daily protein intake was 0.014 $\pm$ 0.003 mg/g protein. Foods from animal and plaint sources provided 34.25 $\pm$ 18.62% and 65.78 $\pm$ 18.72%, respectively, of total vitamin $B_{6}$. Plasma pyridoxal 5'-phosphate (PLP) concentration was significantly (p<.01 - p<.001) positively correlated to intakes of all other nutrients except vitamin C. However, no significant correlation was found between plasma PLP and nutrient intake. Vitamin $B_{6}$ intake only tended to have a positive correlation with plasma PLP concentration. Plasma total cholesterol was correlated to plasma PLP concentration (p<.05). Plasma PLP had no correlation with levels of glucose, triglyceride, and albumin. These results confirm that the present Korea RDA for vitamin $B_{6}$ of 1.4mg/d based on 0.02 mg/g protein is adequate.

• Journal of Nutrition and Health
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• v.28 no.4
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• pp.321-330
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• 1995

Concentrations of total vitamin B-6 in human milk as well as individual, B-6 vitamers have important implications for the nutritional management of breast-fed(BF) infants. Vitamin B-6 status was assessed in 3 groups of infants : two groups preterm (PT) BF infants whose mothers were supplemented with 2 or 27mg pyridoxine(PN)-HCI ; a sub group of formula-fed (FF) PT infants. Mothers and infants were assessed weekly during the 28-day post feeding. Throughout the neonatal period, levels of total vitamin B-6 and percentages of pyridoxal(PL) in breast milk were lower in PT than T mothers, even in mothers supplemented with 27mg PN-HCI. Total vitamin B-6 levels in PT milk paralleled maternal supplementation but percentage distributions of B-6 vitamers did not change. Vitamin B-6 intakes of BF preterm infants paralleled their mothers' level of infants in the 2mg group was suggested by vitamin status parameters. Vitamin B-6 inadequacy of infants correlated with their plasma pyridoxal-5-phosphate(PLP) levels and erythrocyte alanine aminotransferase(E-ALAT) activity; all parameters such as plasma PLP, PL/PLP ratio and stimulation % of E-ALAT were highest for FF PT infants. The positive correlation of vitamin B-6 levels in breast milk gestational age may contraindicate its adequacy for some PT infants.

• Journal of fish pathology
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• v.6 no.2
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• pp.133-142
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• 1993

Vitamin B6(pyridoxine, pyridoxamine. and pyridoxal) is a dietary requirement in relatively small quantities for growth, health, and function in animals and fish. The metabolically active B6 is pyridoxal-5-phosphate(PLP). It does function as a coenzyme in number of enzymes(PLP-dependent enzymes) in which amino acids are metabolized, including decarboxylases, aminotransferases, sulfhydrases, tryptophanase, and hydroxylases. Vitamin B6 requirement is higher for fish because fish are fed much higher protein diet than land animals. B6 is also involved in metabolism of carbohydrates and lipids and essential for the synthesis of heme and serotonin. Deficiency signs in fish develop quickly, in cluding nervous disorders, convulsions, poor swimming coordination, skin lesions, edema, exophthalmos, and tetany. The conversion of vitamin B6 to metabolically active form(PLP) is catalyzed by pyridoxal kinase and pridoxine(pyridoxamine) oxidase. In this review, we summarized in detail the enzymatic studies on vitamin B6 metabolism and about the mechanisms and properties of a PLP-dependent enzyme.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.736-738
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• 2003

Ornithine decarboxylase (ODC) is the key enzyme in the synthetic pathway of polyamines. This enzyme is a homodimeric and a pyridoxal 5-phosphate (PLP) dependent enzyme. We have isolated, a cDNA clone encoding ODC from brain cDNA library constructed from flounder (Paralichthys olivaceus). The ODC cDNA contained a complete ORF consisting of 460 amino acids and one stop codon with comparison to nucleotide sequences of the flounder, zebrafish and rat ODC genes, the ODC genes were highly conserved. The transcription of ODC was analyzed with reverse transcription-polymerase chain reaction (RT-PCR) species in brain, kidney, liver, and embryo.