Degradation of Insulin and Glucagon in Isolated Liver Endosomes: Functional Relationships with ATP-Dependent Endosomal Acidification and Partial Characterization of Degradation Products

During the cooking, processing, and storage of food products, a whole range of browning reactions occurs, initiated by the reaction of a carbohydrate with a compound possessing a free amino group. Melanoidins formed, influence food quality, mainly their colour, their flavour, and their antioxidant activities. Melanoidins are complex Maillard reaction products. We developed a method to isolate coffee melanoidins and melanoidins from toasted oak wood. We noted that coffee is richer in melanoidin compounds than oak wood. We presented a partial characterization of melanoidins fractions from toasted oak heartwood, and a comparison with melanoidins from roasted coffee. Mass spectra of the fractions isolated from toasted oak wood indicate the presence of pentose and hexose-based oligosaccharides with different degrees of polymerisation. The presence of the oligosaccharide moieties, as well as their degradation products found in the oak wood melanoidins, supports the postulated carbohydrate-based origin of melanoidins.

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Degradation of glucagon in isolated liver endosomes. ATP-dependence and partial characterization of degradation products

Biochemical Journal ◽

10.1042/bj2800211 ◽

1991 ◽

Vol 280 (1) ◽

pp. 211-218 ◽

Cited By ~ 17

Author(s):

F Authier ◽

B Desbuquois

Keyword(s):

Degradation Products ◽

Glucagon Receptor ◽

Free System ◽

Chloroquine Treatment ◽

Endosomal Acidification ◽

A Cell ◽

Poly Ethylene ◽

Gradient Fractionation

Endosomes have recently been identified as one major site of glucagon degradation in intact rat liver. In this study, a cell-free system has been used to assess the role of ATP-dependent acidification in endosomal glucagon degradation and identify the glucagon products generated. Percoll gradient fractionation of Golgi-endosomal fractions prepared 10-30 min after injection of [125I]iodoglucagon showed a time-dependent shift of the radioactivity towards high densities. Regardless of time, the radioactivity was less precipitable by trichloroacetic acid (Cl3Ac) at high densities than at low densities. Chloroquine treatment slightly increased the density shift of the radioactivity and decreased its Cl3Ac-precipitability throughout the gradient. Incubation of endosomal fractions containing [125I]iodoglucagon in 0.15 M-KCl at 30 degrees C resulted in a time- and pH-dependent generation of Cl3Ac-soluble radioactivity, with a maximum at pH 4 (t1/2, 7 min). At pH 5, 1,10-phenanthroline, bacitracin and p-chloromercuribenzoic acid partially inhibited [125I]iodoglucagon degradation. At pH 6-7, ATP stimulated [125I]iodoglucagon degradation by 5-10-fold and caused endosomal acidification as judged from Acridine Orange uptake. The effects of ATP were inhibited by chloroquine, monensin, N-ethylmaleimide and dansylcadaverine. Poly(ethylene glycol) (PEG) precipitation of the radioactivity associated with endosomes showed that lowering the pH below 5.5 caused dissociation of the glucagon-receptor complex, and that, regardless of incubation conditions, all degraded [125I]iodoglucagon diffused extraluminally. On h.p.l.c., at least three products less hydrophobic than [125I]iodoglucagon were identified in incubation mixtures along with monoiodotyrosine. Radiosequence analysis of the products revealed one major cleavage located C-terminally to Tyr-13 and two minor cleavages affecting Thr-5-Phe-6 and Phe-6-Thr-7 bonds. It is concluded that glucagon degradation in liver endosomes is functionally linked to ATP-dependent endosomal acidification and involves several cleavages in the glucagon sequence.

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Characterization of dissolved material during the initial phase of softwood kraft pulping

TAPPI Journal ◽

10.32964/tj12.1.37 ◽

2013 ◽

Vol 12 (1) ◽

pp. 37-43 ◽

Cited By ~ 1

Author(s):

HANNU PAKKANEN ◽

TEEMU PALOHEIMO ◽

RAIMO ALÉN

Keyword(s):

Mass Transfer ◽

Molecular Mass ◽

Initial Phase ◽

Degradation Products ◽

Kraft Pulping ◽

Reaction Products ◽

Cooking Temperature ◽

Molecular Masses ◽

Aliphatic Carboxylic Acids

The influence of various cooking parameters, such as effective alkali, cooking temperature, and cooking time on the formation of high molecular mass lignin-derived and low molecular mass carbohydrates-derived (aliphatic carboxylic acids) degradation products, mainly during the initial phase of softwood kraft pulping was studied. In addition, the mass transfer of all of these degradation products was clarified based on their concentrations in the cooking liquor inside and outside of the chips. The results indicated that the degradation of the major hemicellulose component, galactoglucomannan, typically was dependent on temperature, and the maximum degradation amount was about 60%. In addition, about 60 min at 284°F (140°C) was needed for leveling off the concentrations of the characteristic reaction products (3,4-dideoxy-pentonic and glucoisosaccharinic acids) between these cooking liquors. Compared with low molecular mass aliphatic acids, the mass transfer of soluble lignin fragments with much higher molecular masses was clearly slower.

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ISOLATION AND PARTIAL CHARACTERIZATION OF SALMONELLA PHAGE FROM MAROJARM PLANTS

Al-Azhar Journal of Pharmaceutical Sciences ◽

10.21608/ajps.2012.7156 ◽

2012 ◽

Vol 45 (1) ◽

pp. 113-120

Author(s):

Eman Marie

Keyword(s):

Partial Characterization ◽

Salmonella Phage

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Synthesis and Characterization of Potential and Degraded Impurities of Regadenoson

Current Pharmaceutical Analysis ◽

10.2174/1573412915666190819095255 ◽

2020 ◽

Vol 16 (8) ◽

pp. 1130-1139

Author(s):

Singaram Sathiyanarayanan ◽

Chidambaram Subramanian Venkatesan ◽

Senthamaraikannan Kabilan

Keyword(s):

Mass Spectra ◽

Degradation Products ◽

Hplc Method ◽

Forced Degradation ◽

Spectroscopic Techniques ◽

A2a Adenosine Receptor ◽

Degradation Study ◽

Related Substances ◽

Adenosine Receptor Agonist

Background: Regadenoson is an A2A adenosine receptor agonist that is a coronary vasodilator and commonly used as a pharmacologic cardiac stressing agents. Methods: HPLC method was used for the analysis of related substances. The degraded impurities during the process were isolated and characterized by IR, Mass and NMR spectral analysis. Results: Forced degradation study of regadenoson under conditions of hydrolysis (neutral, acidic and alkaline) and oxidations suggested in the ICH Q1A(R2) was accomplished. The drug showed significant degradation under all the above conditions. On the whole, five novel degradation products were found under diverse conditions along with process related impurities which were not reported earlier. Conclusion: All the degradation products were well characterized by using advanced spectroscopic techniques like IR, 1H NMR, 13C NMR and Mass spectra. The identification of these impurities will be productive for the quality control during the production and stability behavior of the regadenoson drug substance.

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