Amino group lysine acylation

The acyl azide is subject to nucleophilic attack, and is most reactive toward primary amino groups (lysine), but will also react with tyrosine hydroxyl, cysteine sulfhy-dryl, and serine hydroxyl groups (Eq. 4.11) ... 

Effect of acylation. Formation of lysinoalanine from lysine re-quires the participation of an e-amino group of a lysine side chain. Therefore, it was expected that protection of amino groups by acylation (acetylation, succinylation, etc.), would reduce ly-sinoalanine formation under alkaline conditions, if the protective group (s) survived the treatment. Results in Tables strikingly demonstrate that acetylation of wheat gluten prevents lysinoala-nine formation. 

Lysine has metabolic properties that set it apart from the other amino acids. It does not accept from other labeled amino acids (14S), and it is resistant to the introduction of deuterium (14Tl from the body fluids. It is not transaminated by crude animal transaminase preparations (jt6) and it is not deaminated by d- nor L-amino acid oxidase preparations unless the a-amino group is acylated (77, 1S9). From these observations it mi t be anticipated that the metabolism of lysine is not initiated by its converaon to the a-keto analog, a-keto-e-aminocaproic acid. 

The side-chain amino group of lysine is a strong nucleophile, the reactivity of which cannot be suppressed by protonation, so it must be protected at all times. Acyl groups such as formyl, which is stable to alkali, ammonia, and hydrogenation but sensitive to mild acid, and trifluoroacetyl (see Section 3.9), which is stable to piperidine and... 

A Streptomyces enzyme that catalyzes hydrolysis of capsaicin is described by Koreishi et The substrate is an A -vanillyl aliphatic amide, and the authors found that their enzyme also accepted A lauroyl amino acids as substrates. The enzyme was used successfully to catalyze the reaction in the opposite direction, driving the equilibrium toward synthesis by running it in buffer containing 78% glycerol. Yields of 5-40% were obtained for a wide range of natural L-amino acids. In the case of L-lysine the enzyme catalyzed acylation at both amino groups, with a clear preference for the e-NH2. 

From Nocardia strains several closely related compounds (nocobactins, formo-bactin, amamistatins) were isolated that contain three typically Fe " binding sites, two hydroxamate units, and ahydroxyphenyloxazole stmcture (cf. Sect. 3.2 below). The C-terminus is A-hydroxy-cyc/o-Lys bound to a long chain 3-hydroxy fatty acid, whose hydroxy group is esterified by A -acyl-A -hydroxy-Lys, the a-amino group of which is bound to 2-o-hydroxyphenyl-5-methyl-oxazole-4-carboxylic acid (Table 4). For the amamistatins the configuration of the cyclic lysine was determined as L, the open one as d, and that of C-3 of the fatty acid as (S). The involvement in the iron metabolism was not investigated. 

The aerobic pathway of metabolism (pathway 1) (Fig. 7.77) produces trifluoroacetyl chloride, a highly reactive acyl chloride, which can react with nucleophiles such as amino groups similar to those on proteins. Alternatively, reaction with water yields trifluoroacetic acid. Trifluoroacetylchloride is the probable reactive metabolite that trifluoroacylates protein, most probably at lysine residues (Fig. 7.77). Removal of the trifluoroacyl moiety from the... 

Insulin detemir is a long-acting insulin analogue that lacks threonine at the B30 position and is acylated with a 14-carbon myristoyl fatty acid side-chain at the epsilon-amino group of the lysine in the B28 position. This stimulates binding to albumin and increases the half-life, extending its duration of action. 

It has been suggested that the modification of the protein s isoelectric point could result in an alteration of its pharmacokinetic profile. Avidin acylation was performed by lysine amino group derivatization with succinyl anhydride or other anhydrides, which allowed the isoelectric point to be shifted to more acidic values, depending on the level of modification. Indeed, the protein anionization induced a reduction of accumulation in the liver, but resulted only in a limited prolongation of residence time in the circulation [30, 31]. 

Transglutaminase Transfer of acyl groups between the y-carboxyamide group of peptide-bound glutamine residues and various amines, including the -amino group of peptide-bound lysine, to form intra- and inter-molecular e-(y-glutamyl)lysine... 

Since lysinoalanine and at least one D-amino acid are toxic to some animals (35), we wished to distinguish their effects in alkali-treated proteins. Such discrimination is possible, in principle, since we have found that acylating the e-amino group of lysine proteins seems to prevent lysinoalanine formation. Since lysinoalanine formation from lysine requires participation of the e-amino group of lysine side chains, acylation of the amino group with acetic anhydride is expected to prevent lysinoalanine formation under alkaline conditions if the protective effect survives the treatment. This is indeed the case (16). 

Several of the proteins of the Golgi transport system are AT-acetylated at either the amino terminal or the e-amino group of a lysine residue. Acylation may be either cotranslational or posttranslational. Amino terminal acylation protects the proteins from degradation, and various acylations are required for the assembly of multisubunit membrane proteins and transport of glycoproteins through the Golgi. 

FIGURE 16.10 Hapten determinants formed by penicillins that contain a p-lactam ring linked to various side chains (R). The primary route of haptenation involves acylation of the E-amino group of lysine residues of serum or cell surface proteins to form a penicilloyl or major antigenic determinant. Isomerization of penicillin leads to the generation of compounds that form disulfide bonds wdth the cysteine sulfhydryl groups of proteins. These epitopes are termed minor determinants. 

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