Pyrrolidone carboxylate

See sodium isethionate sodium-2-pyrrolidone carboxylate. See sodium PCA... 

Menthyl chloroformate, chiral derivatizing reagent, 6 76t Menthyl esters, 24 524 Menthyl pyrrolidone carboxylate, 24 525 Menthyl salicylate, 24 524 physical properties of, 22 14t Menthyl valerate, 24 524 Mentoring, of technical service personnel, 24 346-347... 

RD Dimarchi, JP Tam, SBH Kent, RB Merrifield. Weak-acid catalyzed pyrrolidone carboxylic acid from glutamine during solid phase peptide synthesis. Minimization by rapid coupling. J Pept Prot Res 19, 88, 1982. 

This enzyme [EC 3.4.19.3], a member of the C15 peptidase family, is also known as pyroglutamyl-peptidase 1,5-oxoprolyl-peptidase, pyrrolidone-carboxylate peptidase, and pyroglutamyl aminopeptidase. This hydrolase catalyzes the conversion of a 5-oxoprolyl-peptide to produce 5-oxoproline and a peptide. The enzyme will not act on the 5-oxoprolyl peptide if the adjacent amino acid is l-proline. Enzyme activity is inhibited by thiol-blocking reagents. 

Fig. 5. Schematic representation of fraction IV (Apo Lp-Gln-II). The disulfide bridge is in position 6 from the NHj-terminus. PCA = pyrrolidone carboxylic acid Gin — glutamine.

IV. Nonenzymic Formation of Pyrrolidone Carboxylic Acid from... 

In this chapter the enzymic reactions mentioned above will be reviewed. In addition, consideration will be given to the detection, determination, and natural occurrence of pyrrolidone carboxylic acid, the nonenzymic formation of pyrrolidone carboxylic acid, and to other information now available about the metabolism of this compound. 

The separation of pyrrolidone carboxylic acid from other organic... 

It is known that peptides and proteins exhibit a higher absorbance at wavelengths below 240 nm than the component amino acids (40, 41) and that the absorbance at 205 nm of peptides and proteins is approximately proportional to the number of peptide bonds. Pyrrolidone carboxylic acid, which has an internal peptide bond, exhibits this type of absorbance, which may be used under appropriate conditions for its quantitative determination. Thus, Orlowski et al. (13) followed the activity of y-glutamyl cyclotransferase by this procedure after incubation of the enzyme with y-glutamyl amino acids, the reaction mixture was passed through a small column of Dowex 50 (H+) in order to remove interfering substances, and the absorbance of the eluate at 205 nm was then determined. 

A number of attempts have been made to determine pyrrolidone carboxylic acid after reduction with sodium in alcohol, zinc and HC1, Na2S204, and other reducing agents in general, these were not successful... 

Recently, the reduction of an N-terminal pyrrolidone carboxylic acid residue of proteins with diborane in tetrahydrofuran or tetramethyl urea was attempted with some success the N-terminal pyrrolidone carboxylic acid residue may thus be identified by its conversion to proline... 

Special procedures (44) are required for the demonstration of N-terminal pyrrolidone carboxylic acid residues in peptides and proteins frequently, pyrrolidone carboxylyl-peptides can be detected by the procedure of Rydon and Smith (SO). Discovery of enzymes capable of cleaving pyrrolidone carboxylic acid from the N-terminus of peptide chains should facilitate studies of this type (45, 46) (see below). 

Pyrrolidone carboxylic acid has been found in the free state in a wide variety of vegetables, fruits, and grasses. Thus, it has been found in... 

Italian rye grass that has been stored at —20° (17). However, it seems to be absent in extracts of fresh grass but appears after drying and in silage (17, 47). It is of interest that while fresh tomato juice does not contain appreciate quantities of pyrrolidone carboxylic acid, this compound represents about 30% of the total organic acid in stored tomato juices (48). These and other reports which have appeared in the literature... 

Abderhalden and Kautzch (77) reported that the heating of dry glutamic acid to 180°-200° led to the formation of essentially optically inactive pyrrolidone carboxylic acid. They obtained optically active l-pyrrolidone carboxylic acid by heating L-glutamic acid at 150°-160° followed by fractional crystallization of the product. These workers also observed that treatment of optically active pyrrolidone carboxylic acid with strong mineral acid led to its conversion to optically active glutamic... 

Wilson and Cannan (18) reported detailed observations on the equilibrium and velocity constants in the glutamic acid—pyrrolidone carboxylic acid system in dilute aqueous solution. They found that the conversion of glutamic acid to pyrrolidone carboxylic acid follows the equation for a reversible first-order reaction. The equilibrium constant and the rate at which the equilibrium is achieved depend on the pH of the solution and the temperature. In neutral solutions, the equilibrium favors almost complete conversion of glutamic acid to pyrrolidone carboxylic acid however, the rate of the reaction is very slow and thus only 1% conversion occurs after 2-3 hr at 100°. In weakly acid (pH 4) and alkaline (pH 10) solutions, the conversion of glutamic acid to pyrrolidone carboxylic acid is much faster and about 98% conversion occurs in less than 60 hr. In strong acid (2 N HC1) and base (0.5 N NaOH) the conversion of pyrrolidone carboxylic acid to glutamic acid proceeds rapidly and virtually to completion. Other studies have shown that the conversion of glutamic acid to pyrrolidone carboxylic acid can be carried out within 2 hr at 142° with little alteration of optical rotation (80). 

Using the data of Wilson and Cannan (18), Cleaves (81) was able to show that the rate of formation of pyrrolidone carboxylic acid from glutamic acid in aqueous solution depends directly on the concentration of the ionic species of glutamic acid in solution. Thus, the reactive species are (I), (II), and (IV), while (III) is relatively unreactive. Protonation of the amino group and dissociation of the y-carboxyl group thus makes these groups less reactive carboxylate ion resonance apparently hinders nucleophilic attack by the amino nitrogen. 

---