Transport characteristics of papain-treated brush-border membrane vesicles. Non-involvement of gamma-glutamyltransferase in leucine transport.
Papain treatment of isolated brush border membrane vesicles was carried out to correlate directly the solubilization of gamma-glutamyltransferase with the uptake of leucine. Digestion of membrane vesicles with either soluble or gel-complexed papain resulted in nearly complete removal of gamma-glutamyltransferase. However, the treated vesicles exhibited increased specific activity of leucine and glucose uptake, indicating the non-involvement of the transferase in leucine transport. The partial purification of amino acid and sugar transport function was better controlled with gel-complexed papain. In contrast to the digestion with soluble papain, the treatment with gel-complexed papain did not modify the diffusional components for solutes and ions and did not alter the intravesicular volume. It appears that controlled papain-digestion, resulting in nearly a 2-fold purification of the transport function with high reproducibility and quantitative recovery of uptake, should be useful in future attempts to purify the 'carrier' proteins.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D066298:In Vitro Techniques; D007930:Leucine / Q000378:metabolism*; D051379:Mice; D008871:Microvilli / Q000378:metabolism*; D010206:Papain / Q000494:pharmacology*; D012995:Solubility; D013696:Temperature; D013997:Time Factors; D005723:gamma-Glutamyltransferase / Q000378:metabolism*
D005723:gamma-Glutamyltransferase; D010206:Papain; D007930:Leucine; D005947:Glucose