muramidase and 6-hydroxy-2-5-7-8-tetramethylchroman-2-carboxylic-acid

Chito-oligosaccharides (COS) are being used as important functional materials for many applications due to their bioactivities. The aim of this research has been to assess the relationship between the physico-chemical characteristics, average molecular weight (Mw), acetylation degree (DA), polymerization degree (DP) and specially sequence composition determined by MALDI-TOF MS and the antioxidant properties of COS. These oligosaccharides were obtained by enzymatic depolymerization with chitosanase and lysozyme using a specific chitosan and its reacetylated product. The COS fraction below 5 kDa obtained from chitosanase depolymerization showed the highest capacity to scavenge DPPH radicals and to reduce Fe(3+). A correlation was found between the relative amount of molecules with a given A/D (acetylated vs deacetylated units) ratio within the COS and their antioxidant activity, which could be used to predict the antioxidant behavior of a fraction of chito-oligosaccharides.

Topics: Animals; Antioxidants; Biphenyl Compounds; Chemical Phenomena; Chickens; Chromans; Chromatography, Gel; Chromatography, High Pressure Liquid; Free Radical Scavengers; Glycoside Hydrolases; Magnetic Resonance Spectroscopy; Molecular Weight; Muramidase; Oligosaccharides; Penaeidae; Picrates; Polymerization; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

Oxidative damage to proteins results in biological dysfunctions such as perturbed activity in enzymes, transport proteins, and receptors. Here, we investigated structural damage to proteins induced by free radicals. Structural alterations to lysozyme, human serum albumin (HSA) and beta-lactoglobulin A were monitored by capillary zone electrophoresis. Four well-known antioxidants (quercetin, melatonin, Trolox, and chlorogenic acid) were examined for their ability to inhibit protein damage and to bind to these proteins. Melatonin and chlorogenic acid, which did not bind to any of the three proteins under study, showed scavenging and protective activities well correlated with the amount of free radicals generated. Trolox, which bound only to HSA, was a better protector of HSA than of the two other proteins, indicating that its antioxidant capacity is increased by a shielding effect. Finally, quercetin was a good antioxidant in protecting lysozyme and beta-lactoglobulin A, but its binding to HSA resulted in a pro-oxidant effect that accelerated HSA fragmentation. These results demonstrate that binding of an antioxidant to a protein may potentiate protection or damage depending on the properties of the antioxidant.

Topics: Amidines; Animals; Antioxidants; Chlorogenic Acid; Chromans; Drug Interactions; Free Radicals; Lactoglobulins; Melatonin; Muramidase; Oxidation-Reduction; Protective Agents; Protein Binding; Quercetin

Free radicals derived from one-electron oxidation of the amino acids tryptophan, tyrosine, methionine and histidine have been found to be rapidly (k = 10(7) -10(9) dm3 mol-1 s-1) and efficiently repaired by Trolox C, a vitamin E analogue. The reactions form a relatively stable phenoxyl radical of Trolox C (lambda max = 440 nm; epsilon = 5.4 X 10(3) mol dm-3 cm-1). The radical cation of tryptophan is more rapidly repaired than the neutral tryptophan radical. Repair of tryptophanyl radicals in the enzyme lysozyme has also been observed. The results suggest that a function of alpha-tocopherol in membranes may be the repair of radicals of integral membrane proteins.

Topics: Amino Acids; Antioxidants; Benzopyrans; Chromans; Free Radicals; Histidine; Methionine; Muramidase; Oxidation-Reduction; Pulse Radiolysis; Tryptophan; Tyrosine