Val-Ser-Pro

VSP (= Val-Ser-Pro) (tripeptide) fea mays (corn) (Poaceae) [a-Zein (seed protein) hydrolysate] ACE (10)... 

Figure 4. Automated C-Terminal Sequencing of Ovalbumin (approx. 5-6 nmol) Non-Covalently Applied to Zitex. The expected sequence at the C-terminus is Val-Ser-Pro.

The main toxic pore forming component of P. marmoratus secretion, named pardaxin, was isolated by liquid column chromatography (5). Originally two toxic (5) polypeptides, Pardaxin I and II, were isolated. However, their primary sequences have been found to be identical (6) therefore, the two components most probably represent different aggregates of one polypeptide. This finding is in contrast to the secretion of P. pavonicuSj which contains three toxic polypeptides (8). Pardaxin is a single chain, acidic, amphipathic, hydrophobic polypeptide, composed of 33 amino acids and with a mass around 3500 daltons (5,6). The primary sequence is (6) NHj-Gly-Phe-Phe-Ala-Leu-Ile-Pro-Lys-Ile-Ile-Ser-Ser-Pro-Ile-Phe-Lys-Thr-Leu-Leu-Ser-Ala-Val-Gly-Ser-Ala-Leu-Ser-Ser-Ser-Gly-Gly-Gln-Glu-COOH. 

Amino Acid Content. Amino acid content of field pea products is related to protein level, method of processing, and fraction (starch or protein). The protein fraction contains fewer acidic (glu, asp) amino acids than the starch fraction and more basic (lys, his, arg) amino acids than the starch fraction. Also, there are more aromatic (tyr, phe) amino acids, leu, iso, ser, val, and pro in the protein fraction than in the starch fraction (5). An amino acid profile of pea protein concentrate shows relatively high lysine content (7.77 g aa/16 g N) but low sulfur amino acids (methionine and cystine) (1.08-2.4 g aa/16 g N). Therefore, it is recommended that air classification or ultrafiltration be used because acid precipitation results in a whey fraction which contains high levels of sulfur amino acids (12,23). Also, drum drying sodium proteinates decreases lysine content due to the Maillard reaction (33). 

Fig. 6.28. Breakdown reactions of Val-Tyr-Xaa3-Asp-Xaa5-Ala as a function of pH (Asu = aspartic succinimide) [93] [96], a) Breakdown reactions of Val-Tyr-Pro-Asp-Gly-Ala in pH ranges 1-3, 4-5, and 6-10. b) Breakdown reactions of Val-Tyr-Pro-Asp-Ser-Ala, Val-Tyr-Pro-Asp-Val-Ala, and Val-Tyr-Gly-Asp-Gly-Ala at pH 1. c) Breakdown reactions of the same...

At pH 10 and 70°, the hexapeptides had tm values for degradation of ca. 30-40 h, with the exception of Val-Tyr-Pro-Asp-Val-Ala, the stability of which was much greater (t1/2 ca. 800 h). Here, the hexapeptides containing Asp-Gly or Asp-Ser were clearly much more reactive than the Asp-Val hexapeptide. Interestingly, the D,L-iso-aspartic hexapeptide was the only product formed from the Asp-Gly hexapeptides, and it was the major product from the Asp-Ser hexapeptide (Fig. 6.28,a and c). Formation of the D-Asp hexapeptide was observed for the Asp-Ser hexapeptide, and it was the major one for the Asp-Val hexapeptide, presumably because base-catalyzed epimerization had ample time to occur given the very slow rate of other breakdown reaction. 

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