Homoserine lactone formation

H 0 A-butanoyl-L-homoserine lactone, BHL or C4-HSL Aeromomas hydrophila Aeromonas salmonicida Pseudomonas aeruginosa, Serratia liquefaciens Extracellular protease, biofilm formation. Extracellular protease. Virulence factors - alkaline protease, cyanide, elastase, haemolysin, lectins, pyocyanin, rhaminolipid, RpoS Swarming, protease. 

Solutions of homoserine and its lactone slowly reach equilibrium under most conditions at room temperature. As a result, samples of these derivatives prepared for analysis often gradually change in concentration even during the chromatographic steps, and color values usually reflect such losses. Acidic conditions favor lactone formation, and trifluoroacetic acid at 20°C for 1 hr can be used to convert essentially all of the homoserine (free or in peptides) to the lactone form (Ambler 1965). Alkaline conditions favor homoserine formation, but may often be too harsh for many peptide procedures (see Ambler 1965). 

Witkop achieved selective cleavage of methionyl peptides by a method based on the observation that suUbnium salts of methionine (9) decompose with elimination of the sulfur function and formation of homoserine lactone (10). Highest yields are obtained with use of iodoacetamide as the alkylating agent. 

Scheme 20 Formation of the homoserine lactone as a side reaction in SPPS.

Name for low-molecular-weight substances that trigger cell differentiation in microorganisms (e. g., formation of aerial mycelia, formation of spores) and/or induce formation of secondary products. Often, they are intracellular signalling substances (autoregulators), e.g., the pamamycins and hormaomycin. Chemical signals between organisms of different species have also been observed (e. g., B-factor, homoserine lactones). 

It is well known that sulfonium salts derived from methionine may decompose in many ways. Electron-withdrawing groups on the sulfur atom promote the breakdown of the sulfonium salt by bimolecular or intramolecular nucleophilic displacement. In the case of acetyl-methionine sulfonium derivatives (21) the displacement reaction takes place with the participation of the C-carbonyl group via a 1,5-interactipn, resulting in elimination of the dialkyl sulfide and formation of homoserine iminolactone (22) which on hydrolysis gives homoserine lactone (23) (reaction 17) . Best results are obtained when the reac-... 

These enzymes that are primarily lactonases are now called PTE-like lactonases (PLLs). The lactonase activity plays a role in bacterial communication quorum sensing) (Dickschat, 2009). Virulence and formation of biofilms are regulated by concentration of lactones (N-acetyl-homoserine lactones) in the medium. Thus, the lactonase activity by hydrolyzing lactones acts as a quorum quencher, which in turn inhibits bacterial communication (Amara et al., 2011). The PTE activity is an undiscriminating activity believed to have evolved from lactonases (Afriat et al., 2006 Elias et al., 2008 Afriat-Jurnou et al., 2012 Hiblot et al., 2012). 

The formation of a-ketobutyric acid from homoserine (reaction 5) is based on the observation of Carroll et al. that homoserine or its lactone could be converted to this keto acid by the action of liver extracts under anaerobic conditions, whereas a-aminobutyric acid did not produce any keto acid upon incubation with the enzyme preparation under the conditions of cystathionine cleavage. 

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