Arginine acylation

The amine containing side chains in lysine, arginine, and histidine typically are exposed on the surface of proteins and can be derivatized with ease. The most important reactions that can occur with these residues are alkylation and acylation (Figure 1.8). In alkylation, an active... 

Urea cycle defects Failure to convert ammonia to urea via urea cycle (Fig. 40-5). Coma, convulsions, vomiting, respiratoryfailure in neonate. Often mistaken for sepsis of the newborn. Mental retardation, failure to thrive, lethargy, ataxia and coma in the older child. Associated with hyperammonemia and abnormalities of blood aminogram Low protein diet Acylation therapy (sodium benzoate, sodium phenylacetate) Arginine therapy in selected syndromes Hepatic transplantation... 

It is noteworthy that there is another limiting factor in the choice of amino acid types at the junction sites which affect the enzymatic process of the intein. For example, in the case of SceVMA (also called PI-Seel) from the IMPACT system, proline, cysteine, asparagine, aspartic acid, and arginine cannot be at the C-terminus of the N-terminal target protein just before the intein sequence. The presence of these residues at this position would either slow down the N-S acyl shift dramatically or lead to immediate hydrolysis of the product from the N-S acyl shift [66]. The compatibility of amino acid types at the proximal sites depends on the specific inteins and needs to be carefully considered during the design of the required expression vectors. The specific amino acid requirements at a particular splicing site depends on the specific intein used and is thus a crucial point in this approach. 

Fig. 3.7. Adenylation reaction. (A) Stereo representation of a superposition of the MoaD-MoeB complex in its apo-state (red), in complex with ATP (yellow) and after formation of the acyl adenylate (blue). (B) Proposed reaction scheme for the formation of the acyl adenylate. Arg refers to the second arginine originating either from the second subunit in case of MoeB and hetereodimeric El enzymes,...

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 use of suspended substrates proved very useful in the production of arginine-based surfactants. In this two-step procedure, one amino group of a diami-noalkane was acylated with Z-Arg [55]. This step was done in a melted phase constituted by substrates, and quantitative yields were observed without a catalyst present. Subsequently, the second free amino group of the diaminoalkane reacted with an Z.-Arg-alkyl ester (kinetic control). This step was performed in aqueous suspension or organic solvent using trypsin as the catalyst [73]. 

Fluoromethyl ketones are one of the most widely used classes of peptidyl a-fluoroalkyl ketones, second only to trifluoromethyl ketones. Peptidyl fluoromethyl ketones are very effective as irreversible inhibitors of cysteine proteases the first reported use of a fluoromethyl ketone compound was the use of Z-Phe-Ala-CH2F as an irreversible inhibitor of cathepsin BJ2,31 Today, many lysine and arginine derivatives have been synthesized as potential inhibitors for trypsin and trypsin-like enzymesJ3 There are four basic methods for the synthesis of peptide fluoromethyl ketones (1) the reaction of HF with peptide diazomethyl ketones (Section 15.1.4.1.1), (2) a halogen-exchange reaction with a chloro-, bromo-, or iodomethyl ketone (Section 15.1.4.1.2), (3) a Henry nitro-aldol condensation reaction (Section 15.1.4.1.3), and (4) a modified Dakin-West acylation reaction (Section 15.1.4.1.4). 

The reactions are catalyzed by acyl-CoA amino acid A-acyltransferase, of which two distinct A-acyltransferases exist in mammalian mitochondria. The predominant transferase conjugates medium-chained fatty acyl CoA and substituted benzoic acid derivatives with glycine and is termed an aralkyl-CoA glycine A-acyltransferase, while the other enzyme conjugates arylacetic acid derivatives with glycine, glutamine, or arginine and is an arylacetyl-CoA amino acid A-transferase. 

Westrik and Wolfenden (65) have recently reported that aldehydes, with side chains similar to those comprising the acyl portion of substrates which papain effectively hydrolyzes, were very potent inhibitors of this enzyme. Umezawa and his associates (66) have also recently reported that certain microorganisms (actinomyces) produced an aldehyde, acetyl-L-leucyl-L-leucyl-L-argininal (leupeptin), which inhibits papain. The structures of some of the more effective aldehyde inhibitors of papain are shown in Figure 4. 

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