Peptide fractions

Richter, R., Schulz-Knappe, P., Schrader, M., Standker, L., Jurgens, M., Tammen, H., Forssmann, W.-G. (1999). Composition of the peptide fraction in human blood plasma database of circulating human peptides. J. Chromatogr. B 726, 25-35. 

Recently introduced procedures for the examination of peptides in urine, though restricted only to a certain limited peptide fraction, make the separation of this fraction and analysis of its individual components possible. 

Amino Acids Liberated in the Course of the Hydrolysis of Cehtain Peptide Fractions Isolated from Urine... 

By means of a procedure described above, Hanson and Fittkau (HI) isolated seventeen different peptides from normal urine. One of them, not belonging to the main peptide fraction, consisted of glutamic acid, and phenylalanine with alanine as the third not definitely established component. The remaining peptides contained five to ten different amino acid residues and some unidentified ninhydrin-positive constituents. Four amino acids, i.e., glutamic acid, aspartic acid, glycine, and alanine, were found in the majority of the peptides analyzed. Twelve peptides contained lysine and eight valine. Less frequently encountered were serine, threonine, tyrosine, leucine, phenylalanine, proline, hydroxyproline, and a-aminobutyric acid (found only in two cases). The amino acid composi-... 

Sarnecka-Keller (SI), by use of Bondzynski s method modified by Gawinski, isolated from normal urine a well-defined peptide fraction easily reproducible without change of qualitative composition. Throughout the isolation procedure all factors which may have caused any changes in peptide structure were taken into account. The isolated preparation was substantially similar in general properties to that obtained originally by Bondzynski et al. (B7). 

Proteins from albumin/immunoglobulin-depleted CSF (see Fig. 4) were digested with trypsin and the resultant peptides fractionated by two rounds of chromatography using cation exchange and reversed phase columns. 

The ammonium acetate and acetic acid systems are less resolutive and practical (not UV transparent) than the TFA and TEAP based systems. The former are generally used to generate the acetate salt of peptides. For example, a peptide fraction partially purified with the TEAP system will be reapplied onto an HPLC column after dilution with water (1 1). The column is washed with 1% AcOH and the peptide is eluted by increasing the concentration of MeCN. As another example, the peptide is partially purified using 0.1% TFA, then reapplied onto an HPLC column after dilution with water (1 1). The column is washed first with an ammonium acetate solution to eliminate all TFA, followed by the 0.5% AcOH system to eliminate the ammonium counterion. The peptide is displaced with increasing concentrations of MeCN. 

MW peptide fractions (7). Both the "fresh-cooked" and "cooked- -stored" samples resolve into separate regions, i.e., a hydrophilic region and a hydrophobic region. Hydrophilic peptides are commonly associated with flavors such as "sweet" and possibly, "meaty" and "cooked beef/brothy", whereas the hydrophobic peptides are usually associated with the more undesirable flavors like bitter" and "sour". 

Amarowicz, R. and Shahidi, F. (1997). Antioxidant activity of peptide fractions of capelin protein hydrolysates. Food Chem. 58,355-359. 

Gildberg, A., Bogwald, J., Johansen, A., and Stenberg, E. (1996). Isolation of acid peptide fractions from a fish protein hydrolysate with strong stimulatory effect on Atlantic salmon (Salmo solar) head kidney leucocytes. Comp. Biochem. Physiol. 11, 97-101. 

Further, acidic peptide fractions from Atlantic cod hydrolysate have shown strong immunostimulatory effects, and treatment of these peptides has stimulated the oxidative burst of Atlantic salmon leucocytes (Gildberg et al., 1996). Basically, immunomodulators that enhance the production of oxygen metabolites in macrophages that are responsible for these oxygen metabolites determine the oxidative burst. Oxidative burst reactions are of major importance for the bactericidal power of phagocytes. 

Clegg (1980) reported that bovine serum and high-density lipoprotein (HDL) caused an increase in free fatty acid levels in unpasteurized bulk milk. Lipoprotein free serum, apo HDL, all individual HDL tested, and the unfractionated C-peptide fractions had no lipolytic effect. HDL-lipid in the presence of 2 C-peptides and the combination of HDL-lipid with unfractionated C-peptide caused a considerable stimulation of lipolysis. 

Visser, S., Slangen, K. J., Hup, G. and Stadhouders, J. 1983. Bitter flavor in cheese. 3. Comparative gel-chromatographic analysis of hydrophobic peptide fractions from... 

Phenyl isothiocyanate is also used for peptide sequencing in combination with colored Edman s reagent 4-W-,/V -dimethy]aminoazobenzene-4 -isothiocyanate (DABITC). Prieto (48) used this DABITC-PITC procedure to determine the partial terminal N-NH2 sequence of the low-molecular-weight peptide fraction from bread dough and bread. 

Fig. 6 Reversed-phase chromatography of peptide fractions from curd slurries on a C, 8 (50 X 5 mm) column. Neutrase added (a) followed by starter peptidase (b). Elution was with the following solvent systems solvent A, 0.1% v/v TFA in H20 solvent B, 0.1% v/v TFA in methanol.

Therefore, it appears that the amino acid spectrum in shell matrix proteins and perio-straca of Haliotis is largely a result of the mixing of three different peptide fractions, each one characterized by two amino acids. The six amino acids involved in these three fractions account for about 70 to 80 per cent of the total. The principal difference between shell matrix proteins und periostraca proteins is the high abundance of alanine and serine in the calcified tissue which suggests that the fraction containing these two amino acids is critical in biomineralization processes. 

The action of the gastric and pancreatic enzymes causes the release of small peptides as well as free amino acids, the peptide fraction being the quantitatively dominant one (9). Thus further hydrolysis is crucial, if the dietary protein is to be completely utilized by the organism. The final stages of hydrolysis is associated with the intestinal mucosal cells. Larger peptides are probably hydrolyzed by enzymes at the brush border membrane. Di- and tripeptides may be absorbed as such and hydrolyzed intracellularly (9, 10). 

As concerns the physicochemical and biochemical data obtained in the present study, it becomes clear that the glyco-peptide fraction of microbubble surfactant, isolated from agarose... 

Enzymatic hydrolysates of various proteins have a bitter taste, which may be one of the main drawbacks to their use in food. Arai el al. [90] showed that the bitterness of peptides from soybean protein hydrolysates was reduced by treatment of Aspergillus acid carboxypeptidase from A. saitoi. Significant amounts of free leucine and phenylalanine were liberated by Aspergillus carboxypeptidase from the tetracosapeptide of the peptic hydrolysate of soybean as a compound having a bitter taste. Furthermore, the bitter peptide fractions obtained from peptic hydrolysates of casein, fish protein, and soybean protein were treated with wheat carboxypeptidase W [91], The bitterness of the peptides lessened with an increase in free amino acids. Carboxypeptidase W can eliminate bitter tastes in enzymatic proteins and is commercially available for food processing. 

We thank Prof. Dr. Vladimir Kokryakov, Alexander Kolobov, and Ekaterina Korableva for providing peptide fractions with antimicrobial activities for sequence analysis. Financial support by the Deutsche Forschungsgemeinschaft (DFG) and the European Regional Development Fund (EFRE, European Union, and Free State Saxonia) is gratefully acknowledged. 

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