The effect on amino acid transport of trypsin treatment of rat renal brush border membranes.
Trypsin treatment of isolated rat renal brush border membrane vesicles which preferentially releases L-leucine aminopeptidase (EC 3.4.11.2) decreases their ability to take up a variety of amino acids under Na+ -gradient conditions. Such treatment did not alter the osmotic properties of the vesicles nor affect their fragility. A linear correlation could be demonstrated between the L-leucine aminopeptidase activity of the membranes and the initial rate of uptake of L-leucine and L-proline. Velocity of uptake-concentration dependence studies with these substrates indicate that the major effect of trypsinization is to decrease the maximum velocity (Vmax1) of the low-Km high-affinity system with little effect on the Vmax2 of the high-Km low-affinity transport process and no effect on the apparent Michaelis constants of either. Although the data indicate that L-leucine aminopeptidase activity and uptake of l-leucine and L-proline are affected in parallel, they should not be construed to imply a role of the enzyme in the transport process, especially in view of the global decrease in the uptake of various amino acids and sugars.
D000469:Alkaline Phosphatase / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D007679:Kidney Medulla / Q000378:metabolism*; D007700:Kinetics; D007930:Leucine / Q000378:metabolism; D007931:Leucyl Aminopeptidase / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000502:physiology*; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D014357:Trypsin / Q000494:pharmacology*
D000596:Amino Acids; D008565:Membrane Proteins; D000469:Alkaline Phosphatase; D007931:Leucyl Aminopeptidase; D014357:Trypsin; D007930:Leucine; D005947:Glucose