Salty peptide

Some attempts to reduce sodium chloride intake have been carried out. The first is to use some socUum chloride substitutes. Pottasium chloride is widely used for this purpose. However, pottasium chloride is not thought as perfect sodium chloride substitute because it contains bitter taste. Okai and his associates have synthesized several salty peptides (5). These peptides are expected to be good for hypertension, gestosis, diabetes mellitus and other deseases because they contain no sodium ions. These peptides, however, are not expected to be used as sodium chloride substitutes immediately because of the difficulty of in their synthesis and their cost. Although they are struggling to establish a new synthetic method of peptides in a mass production system with reasonable costs and to improve the salty potency of peptides, they have not dissolved this problem. Since the threshold value of ionic taste is around 1 mM regardless their kinds, it seems to be very difficult to prepare an artificial sodium... 

Taste of Dipeptides Containing Lys and/or Gly. Since Lys-Gly HCl produces the saltiness, we prepared some dipeptides composed of Lys and/or Gly. The results are listed in Table XI. Gly-Lys, of which the amino acid sequence is opposite to the salty peptide Lys-Gly-HCl, produced a weakly sweet taste instead of the salty taste. Dipeptide composed of only Lys or Gly did not any taste. 

Today, it is well-known that peptides or proteins exhibit various kinds of taste. Our group has been researching on the relationship between taste and structure of peptides, BPIa (Bitter peptide la, Arg-Gly-Pro-Pro-Phe-Ile-Val) (7 as a bitter peptide, Om-p-Ala-HCl (OBA), Om-Tau-HCl as salty peptides(2j, and "Inverted-Aspartame-Type Sweetener" (Ac-Phe-Lys-OH) as a sweet peptide(5). The relationship between taste and chemical structure was partly made clear. Since commercial demand for these flavor peptides is increasing, we need to develop new synthetic methods which can prepare these peptides in large scale. We developed the following two methods (1) protein recombination method as a chemical method, (2) enzymatic synthesis using chemically modified enzyme as a biochemical method. 

Seki, T., Y. Kawasaki, M. Tamura, M. Tada, H. Okai, Further study on the salty peptide omithyl-b-alanine some effects of pH and additive ions on the saltiness, J. Agric. Food Chem., 38, p. 25, 1990. 

Shinoda, I., Tada, M., Okai, H. A new salty peptide, omithyl-P-alanine hydrochloride. Pept. Chem. 21st. Proceeding of the Symposium on Peptide Chemistry 1983, p. 43 (1984)... 

Tada M., Shinoda L, Okai H. L-Omithine, a new salty peptide. Journal of the Agricultural and Food Chemistry, 32 992-995 (1984). 

Ohwada et al. [54] synthesized a derivative of the salty peptide V ,V -dicarbobenzoxy-L-omithyl- 3-alamne benzyl ester (Zz-Om(Z)-3-Ala-OBzl) in 1,1,1-trichloroethane using PEG-papain (Fig. 5). 

Figure 5 Synthesis of iy ,A -dicarbobenzoxy-L-omithyl-p-alanine benzyl ester, a derivative of salty peptide, with PEG-papain in 1,1,1-trichloroethane. (From Ref. 54.)...

Some peptides have special tastes. L-Aspartyl phenylalanine methyl ester is very sweet and is used as an artificial sweetener (see Sweeteners). In contrast, some oligopeptides (such as L-ornithinyltaurine HQ. and L-oriuthinyl-jB-alariine HQ), and glycine methyl or ethyl ester HQ have been found to have a very salty taste (27). 

Expansion or enhancement of the proposed mechanism of Nakamura and Okai is shown in Figure 12. Their model is based on the demonstration that several synthetically prepared di- and tri- peptide fragments composed of basic or acidic amino acids, produced individual tastes such as salty (lys-gfy sweet (lys-gfy-asp), sour (asp-glu-glu) and bitter (ser-leu-ala 31). Tlie expanded mechanism we propose is shown in Figure 12 and is based on the data tabulated in Table 1 (31, 38). 

Basic amino acid containing 0-aminoacyl sugars, saltiness, 165-167 Basic amino acid peptides, taste,... 

Wine is one of the most complex and interesting matrices for a number of reasons. It is composed of volatile compounds, some of them responsible for the odor, and nonvolatile compounds which cause taste sensations, such as sweetness (sugars), sourness (organic acids), bitterness (polyphenols), and saltiness (mineral substances Rapp and Mandary, 1986). With a few exceptions, those compounds need to be present in levels of 1%, or even more, to influence taste. Generally, the volatile components can be perceived in much lower concentrations, since our organs are extremely sensitive to certain aroma substances (Rapp et ah, 1986). Carbohydrates (monosaccharides, disaccharides, and polysaccharides), peptides, proteins, vitamins, and mineral substances are among the other wine constituents. 

In the evaluation of contribution to taste, amino acids and peptides are being studied as to sweet, salty, bitter, sour and umaml [brothy mouth-feel, see (19)] sensations. In the production of gravies and soups, proteins are hydrolyzed to smaller molecules which evoke... 

Free amino acids and/or some peptides have some sweetness, bitterness, sourness, saltiness and umami, and are very important as taste substances in foods. 

It has been reported that there are salty stimuli in peptides. Tada et al. (27) inadvertently discovered the synthesized salty dlpeptides, L-0rn-3-Ala HCl, L-Om-Tau HCl, Lys-Tau HCl and L-Orn-Gly HCl having the same intensity taste as NaCl. The salty taste of L-Orn-Tau HCl and Lys-Tau HCl was more intense than that of L-Orn-3-Ala HCl and L-Orn-Gly - HCl. The degree of dissociation of the carboxyl or sulfonyl group in peptides was assumed to contribute to the intensity of the salty taste. These dipeptides may be useful as new seasonings for diabetics and hypertensives because they contain no Na ions. 

Soy sauce is a dark brown salty liquid with a peculiar aroma and a meaty taste. It is the chief seasoning agent in oriental cuisine, but it is becoming increasingly popular in many other regions of the world. It is produced from salt, water, wheat, and soybeans, originally in the batch mode. Today s processes are continuous and much faster than the traditional batch fermentation. They allow the production of 100 million L/year in one factory. The heart of the manufacturing process is a complex sequence of fermentation steps in which the carbohydrates are converted to ethanol and lactic acid and the proteins are broken down to peptides and amino acids. 

The simplest tastant, the hydrogen ion, is perceived as sour. Other simple ions, particularly sodium ion, are perceived as salty. The taste called umami is evoked by the amino acid glutamate, often encountered as the flavor enhancer monosodium glutamate (MSG). In contrast, tastants perceived as bitter or sweet are extremely diverse. Many bitter compounds are alkaloids or other plant products of which many are toxic. However, they do not have any common structural elements or other common properties. Carbohydrates such as glucose and sucrose are perceived as sweet, as are other compounds including some simple peptide derivatives, such as aspartame, and even some proteins. 

Many microbial metabolites are volatile compounds and in terms of their sensory properties can be broken into two broad categories odorants and tastants (Table 1). Tastants include salty, sour, sweet, and bitter compounds such as amino acids, peptides, and sugars. Primary odorants typically are quite volatile and include carbonyl compounds, esters, and terpenes. There is considerable overlap between the two categories lactones, for example, have both taste and odor properties. In keeping with the theme of this symposium, volatile aroma substances will be the primary focus. 

According to several authors, cheese taste is mainly due to the compounds found in the cheese water-soluble extract (WSE) (1, 2). Thus, to study cheese taste, the focus is usually on the cheese WSE which contains small polar molecules such as minerals, acids, sugars, amino acids, peptides and some volatile compounds produced by different processes such as lipolysis, proteolysis microbial metabolism (3). These compounds are responsible for the individual taste sensations like sourness, bitterness and saltiness which are the main taste descriptors for cheese. However, in a complex mixture they also exert otiier taste sensations due to taste / taste interactions (4). Peptides are generally considered to be the main bitter stimuli in cheese (5). However, it was shown that in goat cheese, bitterness resulted mainly from die bitterness of calcium and magnesium chlorides, partially masked by sodium chloride (6). 

The results of omission tests (12) including other compounds in WSE and attributes are reported in Table 3. Cheese sourness was explained by die enhancing effect of sodium chloride on the sourness due to hydronium ions concentration. Cheese bitterness was explained by the enhancing matrix effect on bitterness due to small peptides. Cheese saltiness was respectively explained by a partially masking effect of die matrix on the WSE salty taste due to sodium chloride. 

Importantly, salt-induced peptide formation could provide an abiotic route for the formation of peptides directly from amino acids in concentrated NaCl solutions containing copper ions. Montmorillonite and similar minerals apparently promote the condensation reaction that could have taken place in evaporating tidal pools -Darwin s warm little ponds - where the required salty brine solutions were easily available. Obviously, this is a likely and hence a credible prebiotic scenario. There might a pearl hidden beneath muddy waters. Besides, it is fascinating to assume that the primitive enolase enzyme known to be a highly conserved ancient enzyme could have evolved in an RNA-peptide world. Enolase catalyzes the for enantio-selective carbon-carbon bond addition of water to phosphoenol pyruvate to yield D-2-phospho-glycerate. 

Short oligopeptides play an important role in the sensorial appreciation of food and much attention has been paid to the relationship between the structure of peptides and their taste, based on four basic taste sensations (sweet, bitter, sour and salty). 

Three fragments of the delicious peptide sequence lysine-glycine, serine-leucine-alanine and aspartic acid-glutamic acid-glutamic acid possess separately umami/salty, bitter and sour taste respectively but mixtures or combinations of them produce a similar taste of that corresponding to the complete octapeptide. The synthesis of CBZ-Lys-Gly-OMe and CBZ-Ser-Leu-OMe were carried out using immobilized trypsin and thermolysin. We have studied the influence of reaction medium (pH, temperature and substrate concentration) on the yield and initial reaction rate of synthesis. 

The intensity of the salty taste of Om-P-Ala depends on the pH (Table 1.18). Some peptides exhibit a salty taste, e. g. omithyl-P-alanine hydrochloride (Table 1.17) and may be used as substitutes for sodium chloride. 

The compounds listed in Table 22.10 are used as salt substitutes. Their blends are marketed as diet salts . Peptide hydrochlorides with a salty taste are discussed in Section 1.3.3. 

Peptides, Kke amino acids, can taste bitter, sweet, salty or indifferent. Most natural and synthetic oligopeptides have a bitter taste (see Section 2.3.3.2). A sweet taste indicates dipeptides derived from L-aspartic acid (2-91) and others derived from its lower homologue L-aminomalonic acid (2-92). is always a hydrogen atom or a methyl group, substituents are alkyls or aryls and substituents are esterified carboxyl groups (usually methyl esters, but some ethyl, propyl, isopropyl and other esters are also sweet). The best... 

Rehulka, P. Salplachta, J. Chmelik, J. Improvement of Quality of Peptide Mass Spectra in Matrix-Assisted Laser De-sorption/Ionization Time-of-Flight Mass Spectrometry and Post-Source Decay Analysis of Salty Protein Digests by Using on-Target Washing. J. Mass Spectrom. 2003,38,1267-1269. 

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