Zymogram studies of human intestinal brush border and cytoplasmic peptidases

Zymogram studies of peptide hydrolases from the human intestinal brush border and cytoplasmic fractions produced multiple bands--that is, up to seven--while the brush border membrane produced only a single band of enzyme activity. With all of the substrates tested except L-leucyl-L-leucyl-L-leucine, a band having anodic mobility identical with that produced by the brush border enzymes was produced by the cytoplasmic enzymes. With L-trileucine as a substrate, no overlapping band was produced. This band in the cytoplasmic fraction was heat sensitive, while that in the brush border fraction was not. Thus it would appear that there is a single human intestinal brush border peptide hydrolase capable of hydrolysing a variety of di- and tri-peptides. This peptide hydrolases of the brush border and the cytoplasmic fraction of human intestine are distinct.