Characterization and kinetics of evacuation of peptides resulting from casein hydrolysis in the stomach of the calf

Abstract

A quantitative method for HPLC analysis of the peptides was developed in order to quantify and to compare the peptides leaving the abomasum of preruminant calves fed three different diets: skim milk, aqueous casein solution, casein solution in a mineral medium simulating ultrafiltered milk permeate. It was found that during the first phase of the digestion (0-90 min) the main peptides released from the two casein diets were fragment 106-169 of /c-casein (casein macropeptide, CMP), fragments 1-23 and 165-199 of a8l-casein, and fragment 193-209 of /3-casein. During the same period, slightly more CMP was released after ingestion of skim milk, while the amounts of the other fragments were respectively 10, 2, and 2 times lower than those obtained with casein diets. Thus, CMP was almost the only peptide to be released during the first hour. After that, casein was degraded into small peptides with the three diets, but the amounts released with skim milk were slower than with casein solutions. It was concluded that coagulation contributed to slow down casein degradation and also to retain some peptides. It was supposed that the stomach's role is not only to regulate the release of milk protein but also to select peptides that enter the gut. Taking into consideration the kinetics of liberation of some particular casein peptides, their supposed physiological activities such as regulation in gastric and pancreatic secretions, morphine-like activity, and role in calcium transport were discussed.

Intraluminal immunoreactive caseinomacropeptide after milk protein ingestion in humans

“…These results agree with those obtained in animals where CMP was almost the only peptide released from the abomasum of preruminant calves during the first hour of digestion of a casein diet or skim milk diet [2,3]. These results also confirm those of Chabance et al [5] who detected, using RP-HPLC, the presence of CMP in the stomach and duodenum of human volunteers after milk protein ingestion.…”

“…The collected effluent samples were assayed for volume after homogenisation, treated with 0.1 mmol/l of the protease inhibitor diisopropylfluorophosphate, frozen at -20 8C, and then lyophilised before used for nitrogen analysis. For CMP Elisa analysis, the effluents were treated, as previously described [2,3]. The lyophilised effluent samples (approximately 30 mg DM) were solubilized in water and precipitated with trichloroacetic acid (TCA) to a final concentration of 12%.…”

“…This 64 amino acid-residues peptide is produced from the cleavage of the Phe 105 -Met 106 bond of j-casein by digestive proteases [1]. CMP has been demonstrated to be among the first peptides to leave the calf's stomach after milk feeding [2,3] and was also detected in either the plasma of newborn or in the stomach, the duodenum and the plasma of adult humans, after milk ingestion [4,5]. CMP is suspected to have diverse biological activities including the passive protection against infection in the intestinal lumen [6], modulation of the release of gastrointestinal hormones (CCK, gastrin, somatostatine) and of gastrointestinal motility [7 -11] or modulation of immune cell proliferation [12].…”

Caseinolytic Specificity of Cardosin, an Aspartic Protease from the CardoonCynara cardunculusL.: Action on Bovine αs- and β-Casein and Comparison with Chymosin

“…These results suggest a relationship between the cleavage by cardosin of the four consecutive bonds in segment Ala 189 -Tyr 193 of -CN and texture defects. (Pélissier et al, 1974); (v3) bond cleaved by calf gastric enzymes in vivo on Rs1-CN or -CN (Yvon and Pélissier, 1987); (v4) bonds cleaved by chymosin on -CN (Guillou et al, 1991). Ney (1979), on the basis of the hydrophobicity of the amino acid side chains, as determined by Tanford (1962).…”

Peptides du lait à activité biologique

“…Selon Sato et al (1986), l'hypothèse la plus probable est que les CPP inhiberaient la précipitation des sels de calcium au niveau de l'intestin grêle et favoriseraient ainsi une absorption de type passif au niveau de l'iléon. Mais le décalage de plusieurs heures entre les relargages stomacaux du calcium et des CPP, mis en évidence par Péllissier et al (1983) et Yvon et Pélissier (1987) chez le veau pré-ruminant, soulève plusieurs questions montrant la complexité de ce mécanisme: y-a-t-i1 resolubilisation intestinale par les CPP des sels de calcium précipités ? sous quelle forme saline se trouvent ces sels de calcium ?…”