Hydrolysis of poly-L-methionyl proteins by some enzymes of the digestive tract

Poly-L-lysine and multioligo(L-methionyl) poly-L-lysine as nutritional sources of essential amino acids

“…It is noteworthy that efficient hydrolysis of multioligo-(L-methionyl)poly-L-lysine by proteases of the digestive tract, so long as covalently attached methionine did not exceed 60% of the polymer weight and less than half the €-NH2 groups were acylated, could be considered as a serious indication of good bioavailability of the polymer in vivo. The pattern of release of both amino acids from the multichain polymer was similar indeed to that obtained in the case of poly(L-methionyl)casein (Gaertner and Puigserver, 1986) under similar enzyme digestion conditions or in that of whole egg proteins as a result of pepsin-pancreatin digestion (Stahmann and Woldegiorgis, 1975). The use of a rather low protein diet containing gluten and gelatin, which are deficient in lysine and methionine, respectively, and supplemented with the branched-chain polymer confirmed this observation.…”

“…In Vitro Digestibility Studies. Polylysine samples containing a number of covalently attached oligomethionine of different average chain lengths were successively digested by hog pepsin, activated pancreatic juice, and hog aminopeptidase as already detailed by Gaertner and Puigserver (1986). The resulting hydrolysates were 3-fold diluted with a 0.2 M sodium citrate buffer, and their amino acid composition was subsequently determined with the autoanalyzer.…”

“…L-methionine onto the e-amino groups of casein and ßlactoglobulin by the IV-carboxy anhydride method resulted in the preparation of modified proteins in which as much methionine as 30% of protein weight was covalently attached in the form of polymethionine of an average chain length of eight residues (Gaertner and Puigserver, 1984a). The bioavailability of covalently attached methionine could be derived from in vitro enzyme digestion experiments in which the successive hydrolysis of methionine polymers by gastric, pancreatic, and intestinal enzymes was quantitatively estimated (Gaertner and Puigserver, 1986). An alternative means to prevent the possible deteriorative reactions occurring in food proteins when they are sup- plemented with free essential amino acids may be the use of synthetic amino acid polymers provided that they are efficiently hydrolyzed by the enzymes of the digestive tract.…”

Absorption of Oligo-L-[35S]methionine after Feeding of a Low Casein or a Low Soybean Protein Isolate Diet in Rats

“…Dietary proteins are known to potentiate the exocrine pancreatic secretion in the rats (12,13). Gaertner and Puigserver (16,17) reported that oligo-Lmethionine is digested by pepsin in vitro, which suggests that the gastric digestion of OM is one of the possible mechanisms affecting the difference in the absorptive efficiency of OM between the casein and SPI groups. We also demonstrated the small intestinal transit is faster after the feeding of a low SPI diet than a low casein diet ( 15).…”