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A novel source of methylglyoxal and glyoxal in retina: implications for age-related macular degeneration.
Aging of retinal pigment epithelial (RPE) cells of the eye is marked by accumulations of bisretinoid fluorophores; two of the compounds within this lipofuscin mixture are A2E and all-trans-retinal dim...Read More
Synthesis and characterization of model compounds of the lysine tyrosyl quinone cofactor of lysyl oxidase.
4-n-Butylamino-5-ethyl-1,2-benzoquinone (1(ox)) has been synthesized as a model compound for the LTQ (lysine tyrosyl quinone) cofactor of lysyl oxidase (LOX). At pH 7, 1(ox) has a lambda(max) at 504 n...Read More
Two amine oxidases from Aspergillus niger AKU 3302 contain topa quinone as the cofactor: unusual cofactor link to the glutamyl residue occurs only at one of the enzymes.
Amine oxidases (EC 188.8.131.52) from Aspergillus niger, AO-I (2 x 75 kDa) and AO-II (80 kDa), were examined to determine the cofactor structure. Inactivated with p-nitrophenylhydrazine, they showed absorp...Read More
Biosynthesis of topa quinone cofactor in bacterial amine oxidases. Solvent origin of C-2 oxygen determined by Raman spectroscopy.
Resonance Raman spectroscopy is an excellent technique for providing structural information on the 2,4, 5-trihydroxyphenylalanine quinone (TPQ) cofactor in copper-containing amine oxidases. This techn...Read More
The active site structure of quinohemoprotein amine dehydrogenase inhibited by p-nitrophenylhydrazine.
Quinohemoprotein amine dehydrogenase (QH-AmDH) catalyzes the oxidative deamination of aliphatic and aromatic amines. The enzyme from Pseudomonas putida has an alpha beta gamma heterotrimeric structure...Read More
Identification of topaquinone, as illustrated for pig kidney diamine oxidase and Escherichia coli amine oxidase.
Pig kidney diamine oxidase was purified to homogeneity. The reaction product of the cofactor with p-nitrophenylhydrazine (pNPH) was liberated with pronase treatment and purified. 1H NMR, uv/vis, and e...Read More
Half-site reactivity with p-nitrophenylhydrazine and subunit separation of the dimeric copper-containing amine oxidase from Aspergillus niger.
Structural properties of dimeric (2 x 75 kDa) copper-containing amine oxidase (EC 184.108.40.206) from Aspergillus niger were studied. The enzyme treated with SDS was dissociated into subunits which showed d...Read More
Spectrophotometric determination of decamethrin and its residues in insecticidal formulations and in water.
Three spectrophotometric methods were developed for the microdetermination of decamethrin in insecticidal formulations and in water. The methods are based on the hydrolysis of decamethrin with methano...Read More
Active-site covalent modifications of quinoprotein amine oxidases from Aspergillus niger. Evidence for binding of the mechanism-based inhibitor, 1,4-diamino-2-butyne, to residue Lys356 involved in the catalytic cycle.
Interactions of two distinct quinoprotein amine oxidases from Aspergillus niger, AO-I and AO-II, with active-site covalent modifiers have been investigated. Both enzymes are inhibited similarly by phe...Read More
An improved purification scheme for an amine oxidase from equine plasma (EPAO), a nonruminant source, is described and the protein's active-site is characterized. EPAO is dimeric and contains one...Read More
A comparative study of three methods for the estimation of total plasmalogens in lingual taste epithelium and other tissues.
The total plasmalogen content of lingual and other tissues was analyzed using the iodine-addition (Method 1), the p-nitrophenylhydrazone (Method 2), and the two-dimensional thin layer chromatography p...Read More
Analytical and mechanistic aspects of the electrochemical oxidation of keto steroids derivatized with phenylhydrazine, (4-nitrophenyl)hydrazine, and (2,4-dinitrophenyl)hydrazine.
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