Spectroscopic studies of quinonoid species from pyridoxal 5'-phosphate.


:To establish the state of protonation of quinonoid species formed nonenzymically from pyridoxal phosphate (PLP) and diethyl aminomalonate, we have studied absorption spectra of the rapidly established steady-state mixture of species. We have evaluated the formation constant and the spectrum of the mixture of Schiff base and quinonoid species. For N-methyl-PLP a singly protonated species with a peak at 464 nm is formed from the unprotonated aldehyde and the conjugate acid of diethyl aminomalonate with a formation constant Kf of 240 M-1. The very intense absorption band with characteristic vibrational structure (most evident as a shoulder at 435 nm) is accompanied by a weaker, structured band at about 380 nm and a weak, broad band at 330 nm. We suggest that the 380-nm band may represent a tautomeric form of the quinonoid compound. Protonation of the phosphate group appears to affect the spectrum only slightly. The corresponding mixture of Schiff base and quinonoid species formed from PLP has a very similar spectrum at pH 6-7. It has a formation constant Kf of 230 M-1 and a pKa of 7.8, which must be attributed to the ring nitrogen atom. The dissociated species, which may be largely carbanionic, has a strong structured absorption band at 430 nm and a weaker one, again possibly a tautomer, in the 330-nm region. The analysis establishes that in all species a proton remains on either the phenolic oxygen or the imine nitrogen. Proton NMR spectroscopy, under some conditions, reveals only two components: free PLP and what appears to be Schiff base. However, we suggest that the latter may, in fact, be a quinonoid form, either alone or in rapid equilibrium with the Schiff base. Absorption spectra of quinonoid species formed in enzymes are analyzed and compared with the spectra of the nonenzymic species.






Metzler CM,Harris AG,Metzler DE




Has Abstract


1988-06-28 00:00:00












  • Heparin binding domain of antithrombin III: characterization using a synthetic peptide directed polyclonal antibody.

    abstract::Antithrombin III (ATIII) is a plasma-borne serine protease inhibitor that apparently forms covalent complexes with thrombin. The interaction between ATIII and thrombin is enhanced several thousandfold by the glycosaminoglycan, heparin. We have previously proposed that the heparin binding site of ATIII resides within a...


    pub_type: 杂志文章


    authors: Smith JW,Dey N,Knauer DJ

    更新日期:1990-09-25 00:00:00

  • Physical properties of myosin from aortic smooth muscle.

    abstract::Porcine aortic myosin is a smooth muscle contractile protein similar to its striated muscle counterpart. Electrophoresis in sodium dodecyl sulfate indicates that the molecule consists of three classes of subunits with polypeptide chain molecular weights of 192,000, 19,000, and 15,000. At 277 nm the absorption spectrum...


    pub_type: 杂志文章


    authors: Frederiksen DW

    更新日期:1979-05-01 00:00:00

  • Interaction of alpha-dansylated peptide inhibitors with porcine pepsin: detection of complex formation by fluorescence energy transfer and chromatography and evidence for a two-step binding scheme.

    abstract::Peptide inhibitors, specifically labeled at the alpha-amino terminus by dansylation, have been prepared by utilizing solid-phase peptide synthesis. Changes in fluorescence have been observed upon mixing these peptides with porcine pepsin that can be attributed to the formation of at least two complexes. Energy transfe...


    pub_type: 杂志文章


    authors: Dunn BM,Pham C,Raney L,Abayasekara D,Gillespie W,Hsu A

    更新日期:1981-12-08 00:00:00

  • Structure and mechanism of the 6-oxopurine nucleosidase from Trypanosoma brucei brucei.

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    authors: Vandemeulebroucke A,Minici C,Bruno I,Muzzolini L,Tornaghi P,Parkin DW,Versées W,Steyaert J,Degano M

    更新日期:2010-10-19 00:00:00

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    pub_type: 杂志文章


    authors: Mazzoni MR,Hamm HE

    更新日期:1989-12-12 00:00:00

  • An appraisal of multiple NADPH binding-site models proposed for cytochrome P450 reductase, NO synthase, and related diflavin reductase systems.

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    authors: Daff S

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    pub_type: 杂志文章


    authors: Hutchens TW,Porath J

    更新日期:1987-11-03 00:00:00

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  • A novel delta(3),delta(2)-enoyl-CoA isomerase involved in the biosynthesis of the cyclohexanecarboxylic acid-derived moiety of the polyketide ansatrienin A.

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    pub_type: 杂志文章


    authors: Patton SM,Cropp TA,Reynolds KA

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  • Thermal, chemical, and enzymatic stability of the cyclotide kalata B1: the importance of the cyclic cystine knot.

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    pub_type: 杂志文章


    authors: Colgrave ML,Craik DJ

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  • Oligonucleotide-directed switching of DNA polymerases to a dead-end track.

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    pub_type: 杂志文章


    authors: Guieysse AL,Praseuth D,Grigoriev M,Harel-Bellan A,Hélène C

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  • Expression, purification, characterization, and reconstitution of the large and small subunits of yeast acetohydroxyacid synthase.

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    pub_type: 杂志文章


    authors: Pang SS,Duggleby RG

    更新日期:1999-04-20 00:00:00

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    pub_type: 杂志文章


    authors: Kosen PA,Creighton TE,Blout ER

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  • Kinetics of binding of oligosaccharides to a homogeneous pneumococcal antibody: dependence on antigen chain length suggests a labile intermediate complex.

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    pub_type: 杂志文章


    authors: Maeda H,Schmidt-Kessen A,Engel J,Jaton JC

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  • A novel phosphoprotein inhibitor of protein type-1 phosphatase holoenzymes.

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    pub_type: 杂志文章


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    authors: Newton DL,Klee CB

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    pub_type: 杂志文章


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    authors: Li SJ,Burkey KO,Luoma GA,Alben JO,Marshall AG

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  • Porcine proparathyroid hormone. Identification, biosynthesis, and partial amino acid sequence.

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    pub_type: 杂志文章


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    更新日期:1975-08-12 00:00:00

  • Reduction of ferrylmyoglobin and ferrylhemoglobin by nitric oxide: a protective mechanism against ferryl hemoprotein-induced oxidations.

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  • 1H NMR sequential resonance assignments, secondary structure, and global fold in solution of the major (trans-Pro43) form of bovine calbindin D9k.

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    pub_type: 杂志文章


    authors: Kördel J,Forsén S,Chazin WJ

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  • Beta-elimination of indole from L-tryptophan catalyzed by bacterial tryptophan synthase: a comparison between reactions catalyzed by tryptophanase and tryptophan synthase.

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    pub_type: 杂志文章


    authors: Ahmed SA,Martin B,Miles EW

    更新日期:1986-07-29 00:00:00

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    pub_type: 杂志文章


    authors: Casabon I,Couture M,Vaillancourt K,Vadeboncoeur C

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    pub_type: 杂志文章


    authors: Okret S,Wikström AC,Gustafsson JA

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    pub_type: 杂志文章


    authors: Carlisle TL,Suttie JW

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    pub_type: 杂志文章,评审


    authors: Holt NE,Fleming GR,Niyogi KK

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    pub_type: 杂志文章


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    pub_type: 杂志文章


    authors: Scoville CD,Abraham GN,Turner DH

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    pub_type: 杂志文章


    authors: Yang XY,Schulz H,Elzinga M,Yang SY

    更新日期:1991-07-09 00:00:00