Development and adaptation of protein digestion.
Protein digestion is a complex process in which most aspects have a developmental pattern of activity. Gastric pH and intestinal peptide and amino acid transport as well as the activities of pepsinogen, trypsin, chymotrypsin, enterokinase and intestinal dipeptidases vary during development. No one species has been assessed for all these aspects and it is not possible to present an integrated developmental view of protein digestion. The following developmental changes, however, have been observed. Gastric pH declines, and peptic and pancreatic proteases exhibit increasing activity in pigs and rats after birth. The increase in pigs is gradual over several weeks starting at birth, whereas the increases in the rat begin at 2 wk, just prior to the time of weaning. The activities of dipeptidases in the rat and pig, peptide transport systems in the guinea pig and rabbit and amino acid transport systems in the rat, rabbit, guinea pig and chicken, however, appear (with few exceptions) to be active in the small intestine at the time of birth. Frequently, these activities peak in the neonate and decline during the postnatal period. In the rat, dietary protein tends to increase the activities of pancreatic proteases and intestinal peptidases and to increase the rate of uptake of amino acids by the intestinal epithelium. Individual dietary amino acids also influence amino acid transport systems. The data indicate that most processes in protein digestion undergo marked changes during prenatal and postnatal development and are influenced by the level of feeding and composition of the diet.
D000293:Adolescent; D000375:Aging; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002645:Chickens; D002648:Child; D002675:Child, Preschool; D004044:Dietary Proteins / Q000378:metabolism*; D004063:Digestion; D005314:Embryonic and Fetal Development; D010450:Endopeptidases / Q000378:metabolism; D004765:Enteropeptidase / Q000378:metabolism; D005753:Gastric Mucosa / Q000378:metabolism; D006168:Guinea Pigs; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007223:Infant; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000201:enzymology / Q000502:physiology*; D007700:Kinetics; D010179:Pancreas / Q000201:enzymology; D011817:Rabbits; D051381:Rats; D013045:Species Specificity; D013270:Stomach / Q000201:enzymology / Q000502:physiology*; D013552:Swine
D000596:Amino Acids; D004044:Dietary Proteins; D010450:Endopeptidases; D004765:Enteropeptidase