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Institute of Veterinary Physiology, Winterthurerstrasse 260, CH-8057 Zürich, Switzerland
Transport of selenomethionine (Se-Met) and its sulfur analogue, methionine (Met), across the pig jejunal brush border membrane (BBM) was investigated using isolated BBM vesicles. Experiments were also performed to gain insight into the transport mechanism(s) for selenocystine. Se-Met as well as Met were transported by a single, Na+-dependent, carrier-mediated process common for both amino acids. Evaluation of the kinetic parameters revealed no differences between Se-Met and Met in the maximal transport velocity (Vmax) or in the Michaelis constant (Km). Furthermore, transport of Se-Met and Met showed similar characteristics with respect to electrogenicity and substrate specificity. In addition, evidence was obtained for a competitive inhibition of cystine transport across the BBM by selenocystine and basic amino acids.
KEY WORDS: selenomethionine methionine selenocystine intestinal brush border membrane intestinal transport
1 This work was supported by the Schweizerische Nationalfonds (Grant No 3.807-0.86).
2 Some of these results were presented at the 8th Meeting of the European Intestinal Transport Group in Seggau, Austria, 1987 (1).
Manuscript received 21 September 1988. Revision accepted 5 January 1989.
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