Acylated amino acids description

Description. Sarcosinates (or salts of acyl amino acids) are the condensation products of fatty acids with iV-methylglycine (CH3-NH-CH2-COOH) (or sarcosine). The properties of sarcosinates are similar to those of isethionates. The TEA salts are more soluble than sodium salts around neutral pH. Because of the internal amide chemical function, sarcosinates undergo hydrolysis at extreme pH ranges. 

The synthetase consists of the three modules E1, E2, and E3 (for a complete description, see Sec. II. A). Each module is composed of an activation site forming the acyl or aminoacyl adenylate, a carrier domain which is posttranslationally modified with 4 -phosphopantetheine (Sp), and a condensation domain (Cl, C2) or, alternatively, a structurally similar epimerization domain (Ep). Activation of aminoadipate (Aad) leads to an acylated enzyme intermediate, in which Aad is attached to the terminal cysteamine of the cofactor (El-Spl-Aad) [reactions (1) and (2)]. Likewise, activation of cysteine (Cys) leads to cysteinylated module 2 [reactions (3) and (4)]. For the condensation reaction to occur between aminoadipate as donor and cysteine as acceptor, both intermediates are thought to react at the condensation site of module 1 (Cl). Each condensation site is composed, in analogy to ribosomal peptide formation, of an aminoacyl and a peptidyl site. In this case of initiation, the thioester of Aad enters the P-site, while the thioester of Cys enters the A-site. Condensation occurs and leaves the dipeptidyl intermediate Aad-Cys at the carrier protein of the second module [reaction (5)]. The third amino acid valine is activated on module 3, and Val is attached to the carrier protein 3 [reactions (6) and (7)]. Formation of the tripeptide occurs at the second condensation site C2, with the dipeptidyl intermediate entering the P-site and the valiny 1-intermediate the A-site [reaction (8)]. 

Figure 2 Scheme of domain interactions in ACV synthetases. Domains are presented as circles, linkers are indicated as thin lines, descriptions are as in Fig. 1. Substrate amino acids (A, C, and V) and MATP enter activation domains A1-A3, with MPPi leaving as product. Interactions of the A domains with their adjacent thiolation domains (T1-T3) leads to (amino)acylation with release of AMP. Peptidyl intermediates [AC, LLL-ACV (ACV) and LLD-ACV(ACV )] are boxed, and are produced upon interactions of the thiolation domains with the respective condensation domains. The third thiolation domain interacts with four domains, and the final interactions lead to epimerization and hydrolytic release.

Hydrophobic modification of protein can be achieved either by chemical or enzymatic process to enhance the surface activity. The starting material in such processes may be a polypeptide, a peptide, or an amino acid as the hydrophilic part and a long hydrocarbon chain as the hydrophobic portion. The hydrocarbon can be introduced through acyl, ester, or alkyl linkage [8]. The following is a brief description of acylation and enzymatic modification strategies. 

Description. These surfactants are formed by the acylation of a natural amino acid, the glutamic acid (or a-aminoglutaric acid)... 

In spite of the high level of interest in the asymmetric synthesis of a-amino phosphonic acids, less is known in the case of cyclic a-amino phosphonates. Although in recent years descriptions of promising pharmaceutical applications for cyclic compounds (and acylated derivatives thereof) have been published [61-64], until now no efficient general asymmetric route has been available to prepare this class of a-amino phosphonates. Several attempts at a diastereose-lective synthetic route which were made by the addition of a stoichiometric amount of chiral phosphites to cyclic imines, namely thiazolines, gave only limited diastereoselection ratios of dr=2 1 or below [75,76]. 

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