title: Protease inhibitors and their relation to protease activity in human milk.
abstract: Protease inhibitors and protease (caseinolytic, elastinolytic and esterolytic) activity were analysed in 190 milk samples from 94 mothers from day 1 to day 160 after delivery. The main protease inhibitors in human milk are alpha 1-antichymotrypsin and alpha 1-antitrypsin. As measured by electroimmunoassay, the level of alpha 1-antichymotrypsin in day 1 colostrum was higher than that in normal serum. Trace amounts of inter-alpha-trypsin inhibitor, alpha 2-antiplasmin, alpha 2-macroglobulin, antithrombin III, or antileukoprotease could be demonstrated. According to their protease inhibiting activity, the 53 milk samples from day 1-3 could be divided into two groups. (1) Presence of protease inhibiting activity (n = 35). Both alpha 1-antitrypsin and alpha 1-antichymotrypsin appeared intact and were able to form complexes with added trypsin or chymotrypsin although the major part of alpha 1-antichymotrypsin showed a retarded electrophoretic mobility. The proteolytic inhibiting activity, in spite of the presence of immunoreactive inhibitors (n = 18). alpha 1-antichymotrypsin had a precipitate pattern similar to group 1, whereas alpha 1-antitrypsin had a major fraction with slightly retarded mobility and two minor peaks in the alpha 1-and beta-regions. These precipitate patterns were unchanged on addition of human trypsin or chymotrypsin compatible with the presence of nonreactive inhibitor only. These samples had a caseinolytic and esterolytic activity with an electrophoretic mobility in the beta-region. All samples from day 4 and later had a demonstrable protease inhibiting activity.
mesh_terms: D002918:Chymotrypsin / Q000037:antagonists & inhibitors; D005260:Female; D006801:Humans; D008895:Milk, Human / Q000201:enzymology*; D010196:Pancreatic Elastase / Q000037:antagonists & inhibitors; D010447:Peptide Hydrolases / Q000032:analysis*; D011480:Protease Inhibitors / Q000032:analysis*; D014361:Trypsin Inhibitors / Q000032:analysis
chemical_list: D011480:Protease Inhibitors; D014361:Trypsin Inhibitors; D010447:Peptide Hydrolases; D002918:Chymotrypsin; D010196:Pancreatic Elastase