Of phenyllactate

CBZ-histidyl-p-nitrophenylalanyl derivatives of phenyllactic methyl ester and phenylalanyl methyl ester, 37° (26). 

Ansarin, M. and Woolley, J.G. (1993) The obligatory role of phenyllactate in the biosynthesis of tropic acid. Phytochemistry, 32,1183-7. 

Chesters, N.C.J.E., O Hagan, D. and Robins, R.J. (1994) The biosynthesis of tropic acid in plants evidence for the direct rearrangement of phenyllactate to tropate. /. Chem. Soc. Perkin Trans., 1,1159-62. 

Fuller details on the incorporation of phenyllactic acid (25) into tropane alkaloids have been published." This acid is a better precursor than phenylalanine for the acid fragments of (20), (21), and (22). The significance of this difference is doubtful it may be the result of several causes, the simplest being more effective diversion of phenylalanine into other biosynthetic pathways. None the less phenyllactic acid (25) is clearly a precursor for tropic acid (19) and atropic acid [as (22)] since it is specifically incorporated and moreover labels the alkaloids in the same way as phenylalanine does. 

Application of phenyllactic acid (PLA) in the reduction of fungal mass in food is more desirable compared to other preservatives commonly used in bakery products, such as propionic acid and propionic salts. PLA concentrations effective against fungi from bakery products are usually lower than those required for inhibitory activity. Required concentrations have been reported as L. monocytogenes, 13 mg/ml S. aureus, E. coli, Aeromonas hydrophila, 20 mg/ml, whereas at pH 4 a concentration of < 7.5 mg/ml is enough to inhibit > 50% of bacterial growth (Lavermicocca, Valerio, and Visconti, 2003). 

Lavermicocca, R, Valerio, F., and Visconti, A. 2003. Antifungal activity of phenyllactic acid against molds isolated from bakery products. Applied and Environmental Microbiology 69 634-640. 

Fig. (4). Possible rearrangement of phenyllactic acid or alanine derivatives...

However, this case is extremely rare in nature. An example is the noncompetitive inhibition of phenyllactate versus an amide substrate for carboxypeptidase. In this case, the initial collision complex of substrate and enzyme has an interaction with the terminal carboxyl and the arginine on the enzyme, as well as with the rest of the polypeptide chain, but the aromatic group of the terminal amino add is not in Ae specificity pocket. For it to seat itself requires twisting of the amide bond, which is the rate limiting and energy requiring step of the reaction. Thus, phenyllactate can slip into this pocket and prevent proper seating of the substrate. With an ester substrate, where rotation of the ester bond is not hindered, the collision complex has the specificity pocket filled, and phenyllactate is a competitive inhibitor (Auld Holmquist, 1974). 

Ryan, L. A. M., Dal Bello, R, Czerny, M., Koehler, P, Arendt, E. K. (2009). Quantification of phenyllactic acid in wheat sourdough using high resolution gas chromatography-mass spectrometry. Journal of Agricultural and Food Chemistry, 57, 1060-1064. 

Valerio, R, Lavermicocca, R, Pascale, M., Visconti, A. (2004). Production of phenyllactic acid by lactic acid bacteria an approach to the selection of strains contributing to food quality and preservation. FEMS Microbiology Letters, 233, 289-295. 

Improvement in the production of phenyllactic acid by L. plantamm by addition of phenylalanine and low amounts of tyrosine to the culture medium has been reported (Valerio, Lavermicocca, Pascale, Visconti, 2004). This effect in L. plantamm was further studied by Vermeulen, Ganzle, and Vogel (2006) by the addition of several... 

Through the incorporation studies using D. innoxia, it was found that a P-ketothioester was the intermediate in the biosynthesis of (-)-hyoscyamine and (-)-scopolamine [3-7].Tropinone is formed from the P-ketothioester, and is stereoselectively reduced by a NADPH-dependent oxidoreductase TR-1 to give tropine.Then littorine is formed by adding a phenyllactic acid moiety derived from phenylalanine via phenylpyruvic acid. Regarding the incorporation of phenyllactic acid into tropine and its transformation, it was found that [1,3A C2](—)-hyoscyamine was obtained when [1,3- C2] phenyllactic acid was incorporated into D. innoxia [8]. A transformation therefore occurred on littorine to form (—)-hyoscyamine, and scopolamine was biosynthesized from 6P-hydroxyhyoscyamine by oxidation as described below. 

The same concept was used for sensing a-hydroxycarboxylic acids and diols using chiral boronate 56 (Fig. 17a) containing a displaceable fluorescent group [144]. Formation of the boronate resulted in an increased fluorescence of a couma-rin derived fluorophore, while displacement by the hydroxy acid restored the weaker emission of the free fluorophore. The enantioselective fluorescent response was sufficient for the determination of the enantiomeric excess of phenyllactic acid with a 0.13 (13%) maximum deviation from the actual values. A mathematical algorithm has recently been proposed for the calculation of both stability constants and enantiomeric excess in these indicator-displacement assays [145]. 

The details of the process, shown in Scheme 13.21, involved a series of experiments that showed that carbon from both (5)-[2- C,2- H]phenyllactate and (i )(-)-[2- C,2- H]phenyllactate is incorporated into (-)-tropic add but that only the deuterium from (R)(-)-[2- C,2- ]phenyUactate made it into the alkaloid. The deuterium was found on the carbinol carbon (C-3 ). These data were interpreted as indicating that (S)-[2- C,2- H]phenyllactate must have undergone oxidation to phe-nylpyruvate and then reduction to the (R)-isomer of phenyllactate acid in order to be incorporated. 

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