scholarly journals Dolichol is not a necessary moiety for lipid-linked oligosaccharide substrates of the mannosyltransferases involved in in vitro N-linked-oligosaccharide assembly

1995 ◽  
Vol 310 (3) ◽  
pp. 909-916 ◽  
Author(s):  
I B H Wilson ◽  
M C Webberley ◽  
L Revers ◽  
S L Flitsch
Keyword(s):  
Biosynthetic Pathway ◽  
Substrate Recognition ◽  
Liver Microsomes ◽  
Rat Liver Microsomes ◽  
Enzyme Substrate ◽  
Low Concentrations ◽  
Enzyme Substrate Recognition

Dolichol is utilized in vivo as an unusually large anchor on which the precursor for N-linked oligosaccharides is assembled by a series of glycosyltransferases. The role of dolichol in enzyme substrate recognition is investigated. Thus the biosynthetic intermediate NN′-diacetylchitobiose was chemically linked to either dolichol or the much shorter fully saturated tetraisoprenoid phytanol. Both lipids were used as substrates by a recombinant, soluble beta-1,4-mannosyltransferase. beta-[3H]Mannosylated lipids from this reaction were then used as substrates for the subsequent mannosyltransferases from yeast or rat liver microsomes. It was found that both the dolichyl- and phytanyl-linked substrates were easily mannosylated to form Man5GlcNAc2, with some further mannosylation to Man7GlcNAc2 and Man9GlcNAc2 at low concentrations of lipid-linked substrate. It is concluded that dolichol is not necessary in vitro as part of the substrate for the mannosyltransferases in the biosynthetic pathway for N-glycosylation.

In Vitro Metabolism of E2, G2: Novel Bile Acid-Coupling Camptothecin Analogues, in Rat Liver Microsomes

2021 ◽  
Vol 16 ◽  
Author(s):  
Xiangli Zhang ◽  
Qin Shen ◽  
Yi Wang ◽  
Leilei Zhou ◽  
Qi Weng ◽  
...  
Keyword(s):  
Bile Acid ◽  
Phase I ◽  
Rat Liver ◽  
Deoxycholic Acid ◽  
Liver Microsomes ◽  
Intrinsic Clearance ◽  
Rat Liver Microsomes ◽  
Camptothecin Analogues

Background: E2 (Camptothecin - 20 (S) - O- glycine - deoxycholic acid), and G2 (Camptothecin - 20 (S) - O - acetate - deoxycholic acid) are two novel bile acid-derived camptothecin analogues by introducing deoxycholic acid in 20-position of CPT(camptothecin) with greater anticancer activity and lower systematic toxicity in vivo. Objective: We aimed to investigate the metabolism of E2 and G2 by Rat Liver Microsomes (RLM). Methods: Phase Ⅰ and Phase Ⅱ metabolism of E2 and G2 in rat liver microsomes were performed respectively, and the mixed incubation of phase I and phase Ⅱ metabolism of E2 and G2 was also processed. Metabolites were identified by liquid chromatographic/mass spectrometry. Results: The results showed that phase I metabolism was the major biotransformation route for both E2 and G2. The isoenzyme involved in their metabolism had some difference. The intrinsic clearance of G2 was 174.7mL/min. mg protein, more than three times of that of E2 (51.3 mL/min . mg protein), indicating a greater metabolism stability of E2. 10 metabolites of E2 and 14 metabolites of G2 were detected, including phase I metabolites (mainly via hydroxylations and hydrolysis) and their further glucuronidation products. Conclusion: These findings suggested that E2 and G2 have similar biotransformation pathways except some difference in the hydrolysis ability of the ester bond and amino bond from the parent compounds, which may result in the diversity of their metabolism stability and responsible CYPs(Cytochrome P450 proteins).

Inhibitory Effect of Resveratrol on the Pharmacokinetics of Ticagrelor in Vivo and Vitro

2021 ◽  
Author(s):  
Peng Wang ◽  
Xiao-Xia Hu ◽  
Ying-hui Li ◽  
Nan-Yong Gao ◽  
Guo-quan Chen ◽  
...  
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
In Vitro Study ◽  
Inhibitory Effect ◽  
Control Group ◽  
Rat Liver Microsomes ◽  
Sprague Dawley ◽  
Group B

This study was to evaluate the effect of resveratrol on the pharmacokinetics of ticagrelor in rats and the metabolism of ticagrelor in human CYP3A4 and liver microsomes. Eighteen Sprague-Dawley rats were randomly divided into three groups: group A (control group), group B (50mg/kg resveratrol), and group C (150mg/kg resveratrol ). After 30 minutes administration of resveratrol, a single dose of ticagrelor (18mg/kg) was administered orally. The vitro experiment was performed to examine the influence of resveratrol on ticagrelor metabolism in CYP3A4*1, human, and rat liver microsomes. Serial biological samples were assayed by validated UHPLC-MS/MS methods. In vivo study, the AUC and Cmax of ticagrelor in group B and C appeared to be significantly higher than the control group, while Vz/F and CLz/F of ticagrelor in group B and C were significantly decreased. In vitro study, resveratrol exhibited an inhibitory effect on CYP3A4*1, human and rat liver microsomes. The IC50 values of resveratrol were 56.75μM，69.07μM and 14.22μM, respectively. Our results indicated that resveratrol had a inhibitory effect on the metabolism of ticagrelor in vitro and vivo. It should be paid more attention to the clinical combination of resveratrol with ticagrelor and ticagrelor plasma concentration should be monitored to avoid the occurrence of adverse reaction.

scholarly journals Impact of Deoxycholic Acid on Oesophageal Adenocarcinoma Invasion: Effect on Matrix Metalloproteinases

2020 ◽  
Vol 21 (21) ◽  
pp. 8042
Author(s):  
Fran Quilty ◽  
Anne-Marie Byrne ◽  
John Aird ◽  
Sheeren El Mashad ◽  
Adolfo Parra-Blanco ◽  
...  
Keyword(s):  
Matrix Metalloproteinases ◽  
Deoxycholic Acid ◽  
Therapeutic Strategies ◽  
Oesophageal Adenocarcinoma ◽  
Low Concentrations ◽  
Cancer Invasiveness ◽  
Mrna And Protein Expression

Bile acids (BAs) have been implicated in the development of oesophagitis, Barrett’s oesophagus and oesophageal adenocarcinoma (OAC). However, whether BAs promote cancer invasiveness has not been elucidated. We evaluated the role of BAs, in particular deoxycholic acid (DCA), in OAC invasion. Migration and invasiveness in untreated and BA-treated oesophageal SKGT-4 cancer cells were evaluated. Activity and expression of different matrix metalloproteinases (MMPs) were determined by zymography, ELISA, PCR and Western blot. Finally, human OAC tissues were stained for MMP-10 by immunohistochemistry. It was found that SKGT-4 cells incubated with low concentrations of DCA had a significant increase in invasion. In addition, MMP-10 mRNA and protein expression were also increased in the presence of DCA. MMP-10 was found to be highly expressed both in-vitro and in-vivo in neoplastic OAC cells relative to non-neoplastic squamous epithelial cells. Our results show that DCA promotes OAC invasion and MMP-10 overexpression. This study will advance our understanding of the pathophysiological mechanisms involved in human OAC and shows promise for the development of new therapeutic strategies.

scholarly journals The role of divalent cations in the regulation of microtubule assembly. In vivo studies on microtubules of the heliozoan axopodium using the ionophore A23187.

1976 ◽  
Vol 70 (3) ◽  
pp. 527-540 ◽  
Author(s):  
M Schliwa
Keyword(s):  
Divalent Cations ◽  
Light And Electron Microscopy ◽  
Microtubule Assembly ◽  
In Vivo Studies ◽  
Ionophore A23187 ◽  
Low Concentrations ◽  
Microtubule Formation

Low concentrations of calcium and magnesium ions have been shown to influence microtubule assembly in vitro. To test whether these cations also have an effect on microtubules in vivo, specimens of Actinosphaerium eichhorni were exposed to different concentrations of Ca++ and Mg++ and the divalent cation ionophore A23187. Experimental degradation and reformation of axopodia were studied by light and electron microscopy. In the presence of Ca++ and the ionophore axopodia gradually shorten, the rate of shortening depending on the concentrations of Ca++ and the ionophore used. Retraction of axopodia was observed with a concentration of Ca++ as low as 0.01 mM. After transfer to a Ca++-free solution containing EGTA, axopodia re-extend; the initial length is reached after about 2 h. Likewise, reformation of axopodia of cold-treated organisms is observed only in solutions of EGTA or Mg++, whereas it is completely inhibited in a Ca++ solution. Electron microscope studies demonstrate degradation of the axonemal microtubular array in organisms treated with Ca++ and A23187. No alteration was observed in organisms treated with Mg++ or EGTA plus ionophore. The results suggest that, in the presence of the ionophore, formation of axonemal microtubules can be regulated by varying the Ca++ concentration in the medium. Since A23187 tends to equilibrate the concentrations of divalent cations between external medium and cell interior, it is likely that microtubule formation invivo is influenced by micromolar concentrations of Ca++. These concentrations are low enough to be of physiological significance for a role in the regulation of microtubule assembly in vivo.

Plastoquinone-9 biosynthesis in cyanobacteria differs from that in plants and involves a novel 4-hydroxybenzoate solanesyltransferase

2012 ◽  
Vol 442 (3) ◽  
pp. 621-629 ◽  
Author(s):  
Radin Sadre ◽  
Christian Pfaff ◽  
Stephan Buchkremer
Keyword(s):  
Biosynthetic Pathway ◽  
In Vitro Assays ◽  
Transport Chain ◽  
In Vivo Labelling ◽  
Membrane Bound ◽  
Transformation Processes ◽  
Synechocystis Sp

PQ-9 (plastoquinone-9) has a central role in energy transformation processes in cyanobacteria by mediating electron transfer in both the photosynthetic as well as the respiratory electron transport chain. The present study provides evidence that the PQ-9 biosynthetic pathway in cyanobacteria differs substantially from that in plants. We identified 4-hydroxybenzoate as being the aromatic precursor for PQ-9 in Synechocystis sp. PCC6803, and in the present paper we report on the role of the membrane-bound 4-hydroxybenzoate solanesyltransferase, Slr0926, in PQ-9 biosynthesis and on the properties of the enzyme. The catalytic activity of Slr0926 was demonstrated by in vivo labelling experiments in Synechocystis sp., complementation studies in an Escherichia coli mutant with a defect in ubiquinone biosynthesis, and in vitro assays using the recombinant as well as the native enzyme. Although Slr0926 was highly specific for the prenyl acceptor substrate 4-hydroxybenzoate, it displayed a broad specificity with regard to the prenyl donor substrate and used not only solanesyl diphosphate, but also a number of shorter-chain prenyl diphosphates. In combination with in silico data, our results indicate that Slr0926 evolved from bacterial 4-hydroxybenzoate prenyltransferases catalysing prenylation in the course of ubiquinone biosynthesis.

scholarly journals Inhibition and Induction by Poziotinib of Different Rat Cytochrome P450 Enzymes In Vivo and in an In Vitro Cocktail Method

2021 ◽  
Vol 11 ◽  
Author(s):  
Jinhui Wang ◽  
Feifei Chen ◽  
Hui Jiang ◽  
Jia Xu ◽  
Deru Meng ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Rat Liver ◽  
Clinical Investigation ◽  
Liver Microsomes ◽  
Pharmacokinetic Parameters ◽  
Rat Liver Microsomes ◽  
Cytochrome P450 Enzymes ◽  
Significant Difference

Poziotinib is an orally active, irreversible, pan-HER tyrosine kinase inhibitor used to treat non-small cell lung cancer, breast cancer, and gastric cancer. Poziotinib is currently under clinical investigation, and understanding its drug-drug interactions is extremely important for its future development and clinical application. The cocktail method is most suitable for evaluating the activity of cytochrome P450 enzymes (CYPs). As poziotinib is partially metabolized by CYPs, cocktail probes are used to study the interaction between drugs metabolized by each CYP subtype. Midazolam, bupropion, dextromethorphan, tolbutamide, chlorzoxazone, phenacetin, and their metabolites were used to examine the effects of poziotinib on the activity of cyp1a2, 2b1, 2d1, 2c11, 2e1, and 3a1/2, respectively. The in vitro experiment was carried out by using rat liver microsomes (RLMs), whereas the in vivo experiment involved the comparison of the pharmacokinetic parameters of the probes after co-administration with poziotinib to rats to those of control rats treated with only probes. UPLC-MS/MS was used to detect the probes and their metabolites in rat plasma and rat liver microsomes. The in vitro results revealed that the half-maximal inhibitory concentration values of bupropion and tolbutamide in RLMs were 8.79 and 20.17 μM, respectively, indicating that poziotinib showed varying degrees of inhibition toward cyp2b1 and cyp2c11. Poziotinib was a competitive inhibitor of cyp2b1 and cyp2c11, with Ki values of 16.18 and 17.66 μM, respectively. No time- or concentration-dependence of inhibition by poziotinib was observed toward cyp2b1 and cyp2c11 in RLMs. Additionally, no obvious inhibitory effects were observed on the activity of cyp1a2, cyp2d1, cyp2e1, and cyp3a1/2. In vivo analysis revealed that bupropion, tolbutamide, phenacetin, and chlorzoxazone showed significantly different pharmacokinetic parameters after administration (p < 0.05); there was no significant difference in the pharmacokinetic parameters of dextromethorphan and midazolam. These results show that poziotinib inhibited cyp2b1 and cyp2c11, but induced cyp1a2 and cyp2e1 in rats. Thus, poziotinib inhibited cyp2b1 and cyp2c11 activity in rats, suggesting the possibility of interactions between poziotinib and these CYP substrates and the need for caution when combining them in clinical settings.

scholarly journals Extracellular endosulfatase Sulf-2 harbours a chondroitin/dermatan sulfate chain that modulates its enzyme activity

2021 ◽  
Author(s):  
Rana El Masri ◽  
Amal Seffouh ◽  
Caroline Roelants ◽  
Ilham Seffouh ◽  
Evelyne Gout ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Dermatan Sulfate ◽  
Post Translational Modification ◽  
New Paradigm ◽  
Extracellular Milieu ◽  
Enzyme Substrate ◽  
Enzyme Substrate Recognition ◽  
Substrate Binding Domain

AbstractSulfs represent a class of unconventional sulfatases, which differ from all other members of the sulfatase family by their structures, catalytic features and biological functions. Through their specific endosulfatase activity in extracellular milieu, Sulfs provide an original post-synthetic regulatory mechanism for heparan sulfate complex polysaccharides and have been involved in multiple physiopathological processes, including cancer. However, Sulfs remain poorly characterized enzymes, with major discrepancies regarding their in vivo functions. Here we show that human Sulf-2 (HSulf-2) features a unique polysaccharide post-translational modification. We identified a chondroitin/dermatan sulfate glycosaminoglycan (GAG) chain, attached to the enzyme substrate binding domain. We found that this GAG chain affects enzyme/substrate recognition and tunes HSulf-2 activity in vitro and in vivo using a mouse model of tumorigenesis and metastasis. In addition, we showed that mammalian hyaluronidase acted as a promoter of HSulf-2 activity by digesting its GAG chain. In conclusion, our results highlight HSulf-2 as a unique proteoglycan enzyme and its newly-identified GAG chain as a critical non-catalytic modulator of the enzyme activity. These findings contribute in clarifying the conflicting data on the activities of the Sulfs and introduce a new paradigm into the study of these enzymes.

scholarly journals Safety Assessment of Compounds after In Vitro Metabolic Conversion Using Zebrafish Eleuthero Embryos

2019 ◽  
Vol 20 (7) ◽  
pp. 1712 ◽  
Author(s):  
Arianna Giusti ◽  
Xuan-Bac Nguyen ◽  
Stanislav Kislyuk ◽  
Mélanie Mignot ◽  
Cecilia Ranieri ◽  
...  
Keyword(s):  
High Performance ◽  
Safety Assessment ◽  
Parent Compound ◽  
Liver Microsomes ◽  
Toxicity Testing ◽  
Rat Liver Microsomes ◽  
Metabolic Conversion ◽  
Toxic Potential

Zebrafish-based platforms have recently emerged as a useful tool for toxicity testing as they combine the advantages of in vitro and in vivo methodologies. Nevertheless, the capacity to metabolically convert xenobiotics by zebrafish eleuthero embryos is supposedly low. To circumvent this concern, a comprehensive methodology was developed wherein test compounds (i.e., parathion, malathion and chloramphenicol) were first exposed in vitro to rat liver microsomes (RLM) for 1 h at 37 °C. After adding methanol, the mixture was ultrasonicated, placed for 2 h at −20 °C, centrifuged and the supernatant evaporated. The pellet was resuspended in water for the quantification of the metabolic conversion and the detection of the presence of metabolites using ultra high performance liquid chromatography-Ultraviolet-Mass (UHPLC-UV-MS). Next, three days post fertilization (dpf) zebrafish eleuthero embryos were exposed to the metabolic mix diluted in Danieau’s medium for 48 h at 28 °C, followed by a stereomicroscopic examination of the adverse effects induced, if any. The novelty of our method relies in the possibility to quantify the rate of the in vitro metabolism of the parent compound and to co-incubate three dpf larvae and the diluted metabolic mix for 48 h without inducing major toxic effects. The results for parathion show an improved predictivity of the toxic potential of the compound.

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