Search results for "Substrate Specificity"
showing 10 items of 217 documents
Single Peptide Backbone Surrogate Mutations to Regulate Angiotensin GPCR Subtype Selectivity
2020
Mutating the side-chains of amino acids in a peptide ligand, with unnatural amino acids, aiming to mitigate its short half-life is an established approach. However, it is hypothesized that mutating specific backbone peptide bonds with bioisosters can be exploited not only to enhance the proteolytic stability of parent peptides, but also to tune its receptor subtype selectivity. Towards this end, four [Y]6-Angiotensin II analogues are synthesized where amide bonds have been replaced by 1,4-disubstituted 1,2,3-triazole isosteres in four different backbone locations. All the analogues possessed enhanced stability in human plasma in comparison with the parent peptide, whereas only two of them a…
Mono- and diglucuronide formation from benzo[a]pyrene and chrysene diphenols by AHH-1 cell-expressed UDP-glucuronosyltransferase UGT1A7
1999
Polycyclic aromatic hydrocarbon (PAH)-type compounds induce at least two rat UDP-glucuronosyltransferase isoforms, UGT1A6 and UGT1A7. Among the glucuronidation reactions of PAH metabolites studied, mono- and diglucuronide formation of benzo[a]pyrene and chrysene-3,6-diphenol showed the highest induction factors in rat liver microsomes. Availability of AHH-1 cells stably expressing UGT1A7 allowed us to study whether this PAH-inducible isoform could catalyze benzo[a]pyrene and chrysene-3,6-diphenol glucuronidation. It was found that UGT1A7 indeed catalyzed mono- and diglucuronide formation of both benzo[a]pyrene and chrysene 3,6-diphenols. V79 cell-expressed rat UGT1A6 also catalyzed these re…
Organic carbonates as alternative solvents for asymmetric hydrogenation
2009
Organic carbonates like propylene carbonate (PC) or butylene carbonate (BC) belong to the class of aprotic, highly dipolar solvents (AHD). Interestingly, their potential as solvents for asymmetric catalysis has been overlooked for a long time. The aim of this work is to evaluate organic carbonates and other organic solvents like THF, CH2Cl2, and acetonitrile as well as members of the AHD-family (DMF, DMSO, etc.) as media for homogeneous asymmetric hydrogenation. For this reason cationic Rh-complexes based on chiral phosphine ligands were tested in the hydrogenation of typical benchmark substrates. In several trials, significant advantages of organic carbonates were found. In contrast to DMS…
Substrate Specificity of Vinorine Hydroxylase, a Novel Membrane-bound Key Enzyme of Rauwolfia Indole Alkaloid Biosynthesis
1995
Phosphorylation of GAP-43 (growth-associated protein of 43 kDa) by conventional, novel and atypical isotypes of the protein kinase C gene family: dif…
1996
GAP-43 (growth-associated protein of 43 kDa; also known as neuromodulin, P-57, B-50 and F-1) is a neuronal calmodulin binding protein and a major protein kinase C (PKC) substrate in mammalian brain. Here we describe the phosphorylation by and the site specificity of different PKC isotypes. The conventional PKC beta 1 and the novel PKCs delta and epsilon effectively phosphorylated recombinant GAP-43 in vitro; atypical PKC zeta did not. The K(m) values (between 0.6 and 2.3 microM) were very low, demonstrating a high-affinity interaction between kinase and substrate. All PKC isotypes were shown to phosphorylate serine-41 in GAP-43. When using a 19-amino-acid oligopeptide based on the GAP-43 ph…
Separation by FPLC chromatofocusing of UDP-glucosyltransferases from three developmental stages of Drosophila melanogaster.
1997
Variation of UDP-glucosyltransferase activity, during Drosophila melanogaster development, was analyzed. The endogenous metabolite xanthurenic acid and the xenobiotic compounds 1-naphthol and 2-naphthol were used as substrates. Developmentally regulated differences were observed for the three substrates, suggesting the presence of UDP-glucosyltransferase isoenzymes. This was further confirmed by FPLC chromatofocusing on a Mono P column: seven peaks of UDP-glucosyltransferase activity (pHs: ≥6.3, 5.8, 5.5, 4.9, 4.5, 4.2, ≤4.0) with either single or overlapping substrate specificity were detected. A single xanthurenic acid:UDP-glucosyltransferase activity (pl 5.8) was found throughout develop…
Detection of a plant enzyme exhibiting chlorogenate-dependant caffeoyltransferase activity in methanolic extracts of arbuscular mycorrhizal tomato ro…
2012
When Glomus intraradices-colonised tomato roots were extracted in methanol at 6 degrees C, chlorogenic acid (5-caffeoylquinic acid), naturally present in the extract, was slowly converted by transesterification into methyl caffeate. The progress of the reaction could be monitored by HPLC. The reaction only occurred when the ground roots were left in contact with the hydro-alcoholic extract and required the presence of 15-35% water in the mixture. When the roots were extracted in ethanol, chlorogenic acid was transformed to ethyl caffeate in the same conditions. The reaction was also detected in Glomus mosseae-colonised tomato root extracts. It was also detectable in non-mycorrhizal root ext…
POLYPHENOL OXIDASE ACTIVITY FROM THREE SICILIAN ARTICHOKE (CYNARA CARDUNCULUS L. VAR. SCOLYMUS L. (FIORI)) CULTIVARS: STUDIES AND TECHNOLOGICAL APPLI…
2010
Several papers helped with the development of more methods to control browning, or study thermal polyphenol oxidase (PPO) inactivation, but did not provide any solutions to technological process problems and food process improvement. Artichokes [ Cynara cardunculus L. var. scolymus L. (Fiori)] are susceptible to browning; this alteration could affect and reduce the suitability for its use, fresh or processed. Within this study, the catecholase and cresolase activities of PPO from three different Sicilian artichokes cultivar were characterized with regard to substrate specificity and enzyme kinetics, optimum pH and temperature, temperature and pH stability, and inhibitor test; all of the res…
Biochemistry and medicinal chemistry of the dengue virus protease.
2014
Inhibition of glycosaminoglycan modification of perlecan domain I by site-directed mutagenesis changes protease sensitivity and laminin-1 binding act…
1998
AbstractGlycosaminoglycan attachment to perlecan domain I (173 residues) was completely prevented by site-directed mutagenesis of Ser-65, Ser-71 and Ser-76 as shown by recombinant production in mammalian cells. This did not interfere with the proper folding of the domain's SEA module but enhanced its sensitivity to neutral proteases. Lack of substitution also abolished binding to the two major heparin binding sites of laminin-1.