Search results for "Substrate specificity"
showing 10 items of 217 documents
Differential Enantioselectivity of Murine GlutathioneS-Transferase Isoenzymes in the Glutathione Conjugation ofTrans-3,4-dihydroxy-1,2-oxy- 1,2,3,4-t…
1998
Abstract The kinetics of the glutathione (GSH) conjugation of (+)- and (−)-enantiomers ofanti- as well assyn-3,4-dihydroxy-1,2-oxy-1,2,3,4-tetrahydrobenzo[c]phenanthrene (B[c]PDE) catalyzed by murine GSHS-transferase (GST) isoenzymes has been investigated. Murine GSTs exhibited significant differences in their enantioselectivity toward B[c]PDE stereoisomers. For example, while pi class isoenzyme mGSTP1-1 was virtually inactive toward stereoisomers with 1Sconfiguration [(−)-syn-and (+)-anti-B[c]PDE], these stereoisomers were good substrates for alpha class isoenzyme mGSTA1-2. When GST activity was measured as a function of varying B[c]PDE concentration (10–320 μM) at a fixed saturating conce…
Structural Basis and Enzymatic Mechanism of the Biosynthesis of C9- from C10-Monoterpenoid Indole Alkaloids
2009
Cutting carbons: The three-dimensional structure of polyneuridine aldehyde esterase (PNAE) gives insight into the enzymatic mechanism of the biosynthesis of C(9)- from C(10)-monoterpenoid indole alkaloids (see scheme). PNAE is a very substrate-specific serine esterase. It harbors the catalytic triad S87-D216-H244, and is a new member of the alpha/beta-fold hydrolase superfamily. Its novel function leads to the diversification of alkaloid structures.
Ciprofibrate stimulates protein kinase C-dependent phosphorylation of an 85 kDa protein in rat Fao hepatic derived cells
2000
The effect of ciprofibrate on early events of signal transduction was previously studied in Fao cells. Protein kinase C (PKC) assays performed on permeabilized cells showed a more than two-fold increase in PKC activity in cells treated for 24 h with 500 microM ciprofibrate. To show the subsequent effect of this increase on protein phosphorylation, the in vitro phosphorylation on particulate fractions obtained from Fao cells was studied. Among several modifications, the phosphorylation of protein(s) with an apparent molecular mass of 85 kDa was investigated. This modification appeared in the first 24 h of treatment with 500 microM ciprofibrate. It was shown to occur on Ser/Thr residue(s). It…
Aβ Oligomers and Fibrillar Aggregates Induce Different Apoptotic Pathways in LAN5 Neuroblastoma Cell Cultures
2009
Fibril deposit formation of amyloid beta-protein (Abeta) in the brain is a hallmark of Alzheimer's disease (AD). Increasing evidence suggests that toxicity is linked to diffusible Abeta oligomers, which have been found in soluble brain extracts of AD patients, rather than to insoluble fibers. Here we report a study of the toxicity of two distinct forms of recombinant Abeta small oligomers and fibrillar aggregates to simulate the action of diffusible Abeta oligomers and amyloid plaques on neuronal cells. Different techniques, including dynamic light scattering, fluorescence, and scanning electron microscopy, have been used to characterize the two forms of Abeta. Under similar conditions and …
A novel and rapid prediction assay for the effectiveness of IL-6 receptor specific antisense oligonucleotides by proliferation inhibition of an inter…
2001
Interleukin-6 (IL-6) belongs to a family of cytokines that use receptors consisting of a common signal-transducing chain (gp130). Baf/3 cells transfected with the human IL-6 receptor (IL-6R) and gp130 (Baf/3-gp130/IL-6R) can only grow in medium containing IL-6. We attempted to interrupt the signal transducing pathway of IL-6 with the help of antisense oligonucleotides (ASOs) designed against the IL-6R. We used 18 different kinds of antisense oligonucleotides of overlapping sequences around the translational start codon of the human IL-6R. Sense ASOs were used as a control. The proliferation of cells was analysed by H-thymidine incorporation. Cell surface expression of the IL-6R was assessed…
Enzymatic, physicochemical, nutritional and phytochemical profile changes of apple (Golden Delicious L.) juice under supercritical carbon dioxide and…
2018
The impact of supercritical carbon dioxide (SCCD) (10-60 MPa/45 °C/30 min) and subsequent 10 weeks storage at 4 °C on polyphenol oxidase (PPO), peroxidase (POD) activities, phenolic profile, vitamin C, sugars, physicochemical properties of cloudy apple juices was investigated. No significant changes in sugars and total polyphenols were observed, whereas significant degradation (≈28%) of vitamin C and individual polyphenols (≈18%) was noted after SCCD treatment. After 4 weeks storage only 34% of vitamin C was retained and no vitamin C was detected after this time. Ten weeks of storage caused hydrolysis of sucrose in 15%, whereas degradation of individual polyphenols ranged from 43 to 50% dep…
Addressing substrate glutamine requirements for tissue transglutaminase using substance P analogues
1999
AbstractWe have investigated the effect on the substrate requirements for guinea pig liver (tissue) transglutaminase of a set of 11 synthetic glutamine substitution analogues making up the full sequence of the naturally occurring tissue transglutaminase substrate substance P. While a number of peptide sequences derived from proteins that are well-recognized as tissue transglutaminase substrates have been studied, the enzyme activity using substitution analogues of full-length natural substrates has not been investigated as thoroughly. Thus, our set of substance P analogues only differs from one to other by one amino acid mutation while the length (of the peptide) is maintained as in the nat…
Protease-mediated processing of Argonaute proteins controls small RNA association
2020
SummarySmall RNA pathways defend the germlines of animals against selfish genetic elements and help to maintain genomic integrity. At the same time, their activity needs to be well-controlled to prevent silencing of ‘self’ genes. Here, we reveal a proteolytic mechanism that controls endogenous small interfering (22G) RNA activity in the Caenorhabditis elegans germline to protect genome integrity and maintain fertility. We find that WAGO-1 and WAGO-3 Argonaute (Ago) proteins are matured through proteolytic processing of their unusually proline-rich N-termini. In the absence of DPF-3, a P-granule-localized N-terminal dipeptidase orthologous to mammalian DPP8/9, processing fails, causing a cha…
Enantioselective Zirconium-Catalyzed Friedel−Crafts Alkylation of Pyrrole with Trifluoromethyl Ketones
2009
The first catalytic enantioselective Friedel-Crafts alkylation of pyrrole with 2,2,2-trifluoroacetophenones to give pyrroles with a trifluoromethyl-substituted tertiary alcohol moiety bearing a quaternary stereogenic center is described. The reaction is achieved in the presence of a 3,3'-dibromo-BINOL-Zr(IV) complex to give the expected products with high yields (up to 98%) and good enantioselectivities (up to 93% ee). The absolute stereochemistry of the products has been determined by chemical correlation.
Switch between tyrosinase and catecholoxidase activity of scorpion hemocyanin by allosteric effectors
2008
AbstractPhenoloxidases and hemocyanins have similar type 3 copper centers although they perform different functions. Hemocyanins are oxygen carriers, while phenoloxidases (tyrosinase/catecholoxidase) catalyze the initial step in melanin synthesis. Tyrosinases catalyze two subsequent reactions, whereas catecholoxidases catalyze only the second one. Recent results indicate that hemocyanins can also function as phenoloxidases and here we show for the first time that hemocyanin can be converted to phenoloxidase. Furthermore, its substrate specificity can be switched between catecholoxidase and tyrosinase activity depending on effectors such as hydroxymethyl-aminomethan (Tris) and Mg2+-ions. Thi…