Apparent ionization constants, spectral properties and metal chelation of the cotransaminases and related compounds

Williams, Virginia R.; Neilands, J. B.

doi:10.1016/0003-9861(54)90233-7

Cited by 78 publications

(17 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…for this change estimated from the excitation and fluorescence wavelengths is 94-9-6. This value is about half-way between the reported pK1 values for the ionizations of (XXXIV) to (XXXV) and of (XXXV) to (XXXVI), which are given by Williams & Neilands (1954) as 8-21 and 10-63 respectively. Again at pH9-4, the fluorescence intensity falls to a low value.…”

Section: The Fluorescence Wavelength Changes At Aboutmentioning

confidence: 52%

“…It is immediately apparent that pyridoxal 5-phosphate is but weakly fluorescent, being only about 10% as fluorescent as the 3-hydroxypyridine anion. According to Williams & Neilands (1954), pyridoxal phosphate (aldehyde hydrate form) shows four pK. values, namely <2-5, 4-14, 6-20 and 8-69, which correspond to the equilibria between structures (XXXVIII)-(XLII).…”

Section: The Fluorescence Wavelength Changes At Aboutmentioning

confidence: 99%

“…525mu and A.. 400m,u. This may be due to the trianion of the free aldehyde form (XLIV), since Williams & Neilands (1954) have recorded an absorption peak at 390m,u for pyridoxal phosphate in alkaline solution that may be due to the free aldehyde form (Metzler & Snell, 1955). Pyridoxic acid and its lactone.…”

Section: The Fluorescence Wavelength Changes At Aboutmentioning

confidence: 99%

“…and pK*, from the Forster cycle (see Jaff6, Beveridge & Jones, 1964) for absorption and fluorescence, which is: pK.-pK*, = 107hc (A'-A) (1959). ¶1 Williams & Neilands (1954). where A and A' are the maximum absorption or fluorescence wavelengths of the acid and anion (or conjugate base) respectively. Substituting the known values for the constants h, c and k, and taking T as 2930A (20°c), eq.…”

Section: The Fluorescence Wavelength Changes At Aboutmentioning

confidence: 99%

See 3 more Smart Citations

Fluorescence studies on some hydroxypyridines including compounds of the vitamin B6 group

Bridges¹,

Davies²,

Rd³

1966

Biochemical Journal

123

View full text Add to dashboard Cite

1. The variations with pH (from 36n-sulphuric acid to 10n-sodium hydroxide) of the excitation and fluorescence wavelengths and fluorescence intensity of 2-, 3- and 4-hydroxypyridine and their O- and N-methyl derivatives were investigated. 2. 4-Hydroxy- and 4-methoxy-pyridine were non-fluorescent at all pH values. 3. The cations and dipolar ions of the 3-hydroxypyridine derivatives and the anion of 3-hydroxypyridine were fluorescent, but the neutral forms were not. 4. All the forms of the 2-hydroxypyridine derivatives were fluorescent. 5. Pyridoxol, pyridoxal and its 5-phosphate, pyridoxamine and pyridoxic acid and its lactone were studied similarly. All these compounds, except pyridoxal 5-phosphate, were more fluorescent than 3-hydroxypyridine. 6. The most fluorescent forms of these compounds are the anions, except for pyridoxol, where the dipolar ion was the most fluorescent form. The least fluorescent forms are the neutral molecules. The dipolar ions were appreciably fluorescent in all cases. 7. The most fluorescent form examined was the dianion of pyridoxic acid lactone. 8. The cations were all fluorescent except the cations of 2- and 3-methoxypyridine. All the cations showed excited-state ionization. The excited pK(a) values of these cations were determined and the results are discussed with reference to Weller's (1952) equation relating ground- and excited-state dissociation constants. 9. The pK(a) values for all ionizations undergone by the compounds examined were determined from fluorescence data. 10. Stokes shifts for the various ionic and neutral species of the compounds examined were calculated and are discussed.

show abstract

Section: The Fluorescence Wavelength Changes At Aboutmentioning

confidence: 52%

Section: The Fluorescence Wavelength Changes At Aboutmentioning

confidence: 99%

Section: The Fluorescence Wavelength Changes At Aboutmentioning

confidence: 99%

Section: The Fluorescence Wavelength Changes At Aboutmentioning

confidence: 99%

See 2 more Smart Citations

Fluorescence studies on some hydroxypyridines including compounds of the vitamin B6 group

Bridges¹,

Davies²,

Rd³

1966

Biochemical Journal

123

View full text Add to dashboard Cite

show abstract

“…In enzymatic catalysis, the metal ion is not required because of stabilization by the amino acid side chains of the enzyme 8. The binding of metal by PM at physiological pH is possible because of the unusually acidic ionization constant of the phenolic hydroxyl, pK ∼3.4 9,10. PM can form complexes with a number of transition metal ions but has a preference for Cu 2+ and Fe 3+ 11,12.…”

Section: Introductionmentioning

confidence: 99%

Pyridoxamine: The Many Virtues of a Maillard Reaction Inhibitor

Voziyan

Hudson

2005

Annals of the New York Academy of Sciences

113

View full text Add to dashboard Cite

Pyridoxamine (PM) is one of three natural forms of vitamin B6. It is a critical transient intermediate in catalysis of transamination reactions by vitamin B6-dependent enzymes. The discovery eight years ago that PM can inhibit the Maillard reaction stimulated new interest in this B6 vitamer as a prospective pharmacological agent for treatment of complications of diabetes. PM application in diabetic nephropathy has now progressed to a phase III clinical trial. Investigation of the PM mechanism of action demonstrated that PM inhibits post-Amadori steps of the Maillard reaction by sequestering catalytic metal ions and blocking oxidative degradation of Amadori intermediate. PM also has the capacity to scavenge toxic carbonyl products of sugar and lipid degradation, and to inhibit reactive oxygen species. These multiple activities position PM as a promising drug candidate for treatment of multifactorial chronic conditions in which oxidative reactions and/or carbonyl compounds confer pathogenicity.

show abstract

Photo‐Induced Processes in Vitamin B₆ Compounds

Vilanova

Adrover

Muñoz

et al. 2004

Chemistry & Biodiversity

View full text Add to dashboard Cite

In this work, we applied multi-wavelength stopped-flow spectroscopy (MSFS) to study the chemical equilibria between tautomeric or hydrated forms of various vitamin B6 compounds and the Schiff base formed by epsilon-aminocaproic acid (= 6-aminohexanoic acid) with pyridoxal 5'-phosphate at 25 degrees and variable pH. Since some of these compounds are photosensitive, we analyzed the possible occurrence of any secondary photo-induced processes under the conditions of irradiation in the MSFS equipment (continuous irradiation with light from a 75-W Xe lamp spanning the wavelength range of 200-700 nm). To determine the tautomeric composition of these compounds, the electronic absorption spectra were analyzed by means of log-normal curves. Continuous irradiation of pyridoxamine and pyridoxal 5'-phosphate over the wavelength range of 200-700 nm displaces the chemical equilibrium between the tautomeric or hydrated forms of these compounds. However, the Schiff base of epsilon-aminocaproic acid with pyridoxal 5'-phosphate is insensitive to the radiation used. The photo-induced processes detected in pyridoxamine and pyridoxal 5'-phosphate should be taken into account in examining vitamers by MSFS. In fact, these additional processes should be considered in studying the mechanism of action of vitamin B6-dependent enzymes by the MSFS technique, whenever some free vitamer may be present in solution.

show abstract

Apparent ionization constants, spectral properties and metal chelation of the cotransaminases and related compounds

Cited by 78 publications

References 12 publications

Fluorescence studies on some hydroxypyridines including compounds of the vitamin B6 group

Fluorescence studies on some hydroxypyridines including compounds of the vitamin B6 group

Pyridoxamine: The Many Virtues of a Maillard Reaction Inhibitor

Photo‐Induced Processes in Vitamin B₆ Compounds

Contact Info

Product

Resources

About

Apparent ionization constants, spectral properties and metal chelation of the cotransaminases and related compounds

Cited by 78 publications

References 12 publications

Fluorescence studies on some hydroxypyridines including compounds of the vitamin B6 group

Fluorescence studies on some hydroxypyridines including compounds of the vitamin B6 group

Pyridoxamine: The Many Virtues of a Maillard Reaction Inhibitor

Photo‐Induced Processes in Vitamin B6 Compounds

Contact Info

Product

Resources

About

Photo‐Induced Processes in Vitamin B₆ Compounds