A-Acyl-L-arginine

TABLE 3 Surface-Active Properties of Salts of A-Acyl-L-arginine Esters... 

X 7, 9, 11, 13, 15 R CH3, CH2CH3,(CH2)2CH3 FIG. 1 Structure of A -acyl-L-arginine aUcyl ester derivatives. 

Long-chain A -acyl-L-arginine dipeptides from acid-hydrolyzed collagen CsArg aa, CioArg aa, Ci2Arg aa, CwArg aa, and Ci Arg aa (Fig. 2b) were... 

Ideal chemical conditions for the preparation of pure long-chain V -acyl-L-arginine dipeptides would allow rapid and quantitative acyl bond formation under mild conditions and the avoidance of side reactions while maintaining all the adjacent chiral centers. A number of methodologies have been developed to overcome problems related to reactivity and purity. 

FIG. 2 Structures of lipopeptidic surfactants synthesized from arginine (a) pure lauroyl-L-arginine dipeptides (b) polydisperse Al -acyl-L-arginine dipeptides (c) poly-disperse Al -acyl-L-arginine peptides. 

Vinardell and co-workers [135] studied the irritation of rabbit eye and skin from cationic amino acid-derived surfactants iV-acyl-L-arginine methylesters. They found that amino acid-based surfactants are less irritant than a conventional cationic surfactant, cetrimide. Also, the degree of irritation depends on the chain length of the alkyl group, and a maximum of irritation was observed for Ci2 surfactant. The similar effect was reported for alkyl sulfates before [136], being ascribed to the high monomer concentration of surfactant. 

Catalytic tests were performed in a glass vessel equipped with a stirrer motor. Two monoliths (diameter 4.3 cm, length 4 cm) were mounted in plane on the stirrer axis. The total reaction volume was 2.5 1. Lipase was assayed in the acylation of vinyl acetate with butanol in toluene. Initial reaction rate was followed by GC analysis. Immobilized trypsin was used in the hydrolysis of N-benzoyl-l-arginine ethyl ester (BAEE) in a 0.01 M phosphate buffer pH 8 at 308 K. The reaction was followed by UV-VIS at 253 nm, and reaction rate was calculated in the mass transfer limited situation. 

The difficult preparation of Z-Arg(Z)2-OH, and thus the related low yields associated with earlier methods,f l are conveniently bypassed if persilylated A -(benzyloxy-carbonyl)arginine is acylated with benzyl chloroformate.f 1 This procedure is also well-suited for the preparation of Boc-Arg(Z)2-OH.P l Alternatively, the N -bis-protected derivatives are also obtained in good yields via guanidinylation of N -protected ornithine with N,N -bis-protected guanidinylating reagents (see Section 2.6.1.6).t l For peptide acylation steps, both Z-Arg(Z)2-OH and Boc-Arg(Z)2-OH are mainly used as active esters,f l mixed anhydrides or carbodiimides.P l... 

We have shown by a comparison of the pH dependence of the step characterized by ki that the hydrolysis of the enzyme-acyl compound is the rate-determining step for the enzymatic hydrolysis of the usual amino acid amide substrates. In the case of chymotrypsin, acetyl-L-phenylalanine ethyl ester is hydrolyzed 1,000 times faster than the corresponding amide and in the case of trypsin, benzoyl-L-arginine ethyl ester is hydrolyzed 300 times faster than the corresponding amide. This suggests that for the amide hydrolysis too the second step, the acylation of the enzyme, must be the rate-determining step, since the third step is obviously identical for esters and amides of the same amino acid derivatives. The pH dependence of the chymotrypsin-catalyzed hydrolysis of acetyl-L-tyrosine ethyl ester and acetyl-L-phenylalanine ethyl ester indicates that for these reactions ki and kz are of the same order of magnitude and both contribute to the over-all rate, as shown by Equation (4). 

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