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Phytomedicines Targeting Antibiotic Resistance through Quorum Sensing and Biofilm Formation Associated with Acne Vulgaris
Published in Namrita Lall, Medicinal Plants for Cosmetics, Health and Diseases, 2022
Isa A. Lambrechts, Namrita Lall
Gram-negative and Gram-positive bacteria use quorum sensing as a way to control various physiological activities. Acylated homoserine lactones (AHL) are used as autoinducers by Gram-negative bacteria, whereas Gram-positive bacteria use processed oligopeptide (AL) autoinducers during intraspecies communication (Bassler, 1999).
Ethylmalonic encephalopathy
Published in William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop, Atlas of Inherited Metabolic Diseases, 2020
Methionine is converted normally to homoserine and cysteine. Homoserine is converted to 2-oxobutyric acid which could be a source of ethylmalonic acid. Cysteine is converted to 2-mercaptopyruvic acid which is metabolized to pyruvic acid and thiosulfate and ultimately sulfate [20]. Ethylmalonic acid can be formed via carboxylation of butyryl CoA (Figure 102.1) catalyzed by propionyl CoA carboxylase [21], and this appears to be the source of ethylmalonic acid found in SCAD deficiency and in multiple acylCoA dehydrogenase deficiency [21]. In our patient, loading with medium-chain triglyceride did not greatly increase the excretion of ethylmalonic acid. Ethylmalonic acid could be a product of isoleucine metabolism through the R pathway after racemization of 2-oxo-3-methylvaleric acid, the precursor of alloisoleucine, from the S to the R form, which is then convertible to 2-methylbutyryl CoA, 2-ethyl-3-hydroxypropionyl CoA, and ethylmalonic semialdehyde and then to ethylmalonic acid.
The Modification of Carboxyl Groups
Published in Roger L. Lundblad, Claudia M. Noyes, Chemical Reagents for Protein Modification, 1984
Roger L. Lundblad, Claudia M. Noyes
The above observation that the majority of studies on the chemical modification of carboxyl groups utilize the carbodiimide-mediated reaction(s) is not intended to indicate that there are not other approaches to the modification of aspartyl and glutamyl residues in proteins. Indeed, there are examples of carboxyl group modification with reagents expected to react far more effectively with other nucleophiles. An example of this is the reaction of iodoac-etamide with ribonuclease T1 to form the glycolic acid derivative of the glutamic acid residue as elegantly shown by Takahashi and co-workers.3 Another example is the modification of a specific carboxyl group in pepsin by p-bromophenacyl bromide3 (the use of p-bromo-phenacyl bromide in the specific modification of proteins is not uncommon but is generally associated with the modification of cysteine, histidine, or methionine). In the study of pepsin, optimal inactivation (approximately 12-fold molar excess of reagent, 3 hr, 25°C) was obtained in the pH range of 1.5 to 4.0 with a rapid decrease in the extent of inactivation at pH 4.5 and above (the effect of pH greater than 5.5 to 6.0 on the modification of pepsin cannot be studied because of irreversible denaturation of pepsin at pH 6.0 and above). In studies with a 10% molar excess ofp-bromophenacyl bromide at pH 2.8, 37°C, 3 hr, complete inactivation of the enzyme was obtained concomitant with the incorporation of 0.93 mol of reagent/mole of pepsin (assessed by bromide analysis). Attempts to reactivate the modified enzyme with a potent nucleophile such as hydroxylamine were unsuccessful but reactivation could be obtained withsulfhydryl-containing reagents (i.e., β-mercaptoethanol, 2,3-dimercaptopro-panol, thiophenol). It has been subsequently established that reaction occurs at the β-carboxy group of an aspartic acid residue (formation of 2-/?-bromophenyl-1 -ethyl-2-one β-aspartate).5 These investigators noted that reduction of enzyme under somewhat harsh conditions (LiBH4 in tetrahydrofuran) resulted in the formation of homoserine.
Gram-negative quorum sensing signalling enhances biofilm formation and virulence traits in gram-positive pathogen Enterococcus faecalis
Published in Journal of Oral Microbiology, 2023
Ana Parga, Daniel Manoil, Malin Brundin, Ana Otero, Georgios N. Belibasakis
The AHLs employed in this study were N-Butyryl-DL-homoserine lactone (C4-HSL; Fluka, Thermo Fisher Scientific, Waltham, US), N-(3-Oxobutyryl)-L-homoserine lactone (3-oxo-C4-HSL; University of Nottingham, Nottingham, GB), N-Hexanoyl-L-homoserine lactone (C6-HSL; Sigma-Aldrich, Merck KGaA, Darmstadt, DE), N-Oxohexanoyl-L-homoserine lactone (3-oxo-C6-HSL; University of Nottingham), N-Octanoyl-L-homoserine lactone (C8-HSL; Sigma-Aldrich), N-Decanoyl-L-homoserine lactone (C10-HSL; Sigma-Aldrich), N-Dodecanoyl-L-homoserine lactone (C12-HSL; Sigma-Aldrich), N-Tetradecanoyl-DL-homoserine lactone (C14-HSL; Fluka) and N-Octadecanoyl-L-homoserine lactone (C18-HSL; University of Nottingham).
Alternative approaches to treat bacterial infections: targeting quorum-sensing
Published in Expert Review of Anti-infective Therapy, 2020
Pipat Piewngam, Janice Chiou, Priyanka Chatterjee, Michael Otto
The AHL-acylase, a member of the Ntn-hydrolase superfamily that was first described in the Variovorax paradoxus strain VAI-C, irreversibly hydrolyzes the amide linkage between the acyl chain and homoserine moiety of AHL molecules. This process releases homoserine lactone and the corresponding fatty acid, which do not exhibit any residual signaling activity. Expression of AiiD, an AHL-acylase from Ralstonia strain XJ12B, in P. aeruginosa led to a reduction in its ability to swarm and produce elastase and toxin [123]. The AHL-acylase AhlM from Streptomyces sp. strain M664 decreases the production of virulence factors in P. aeruginosa, including elastase, total protease, and LasA, by reducing the accumulation of AHLs [124]. AhlM is also a penicillin acylase; and penicillin acylases and AHL acylases can often hydrolyze both β-lactams and AHLs [125]. AHL acylases have been found and characterized in many bacteria, such as Ralstonia erythropolis W2, Comamonas spp. strain D1, Shewanella spp. strain MIB015, and Streptomyces spp [118].
Nanoparticles for treatment of bovine Staphylococcus aureus mastitis
Published in Drug Delivery, 2020
Samah Attia Algharib, Ali Dawood, Shuyu Xie
As well as, the nanomaterials have a significant impact on the treatment of S. aureus infection by preventing the biofilm formation whereas, the main component of the biofilm is the glycocalyx with anionic charge, it can interact with the nanoparticles with a positive charge which have the ability to penetrate the thick biofilm (Kulshrestha et al., 2017). Sathyanarayanan et al. (2013), reported that the gold nanoparticles had a significant decrease in the biofilm that was formed by S. aureus. Liu (Liu, 2019), mentioned that using triclosan as an antimicrobial drug in solution only penetrate and killing the S. aureus outside the biofilm; however, loading the triclosan in micellar nanocarrier help in the penetration of staphylococcal biofilm and killing the bacteria over the depth of the biofilm. Also, some authors demonstrated that inhibition of the biofilm could be achieved by interfering with the quorum-sensing systems (QSs), which act as a major regulatory mechanism in biofilm formation (Figure 4) (Singh et al., 2017). Modifying the nanoparticle surface by some substance such as “B-cyclodextrin or N-acylated homoserine lactonase proteins” can switch off the (QSs) and prevent the bacterial communication through interfering with the signal/receptor interaction (Kato et al., 2006; Ortíz et al., 2008).