Characterization of methionine transport in bovine intestinal brush border membrane vesicles
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Abstract
Characteristics of methionine uptake by brush border membrane vesicles of bovine small intestine were investigated. Alkaline phosphatase marked the brush border membrane fraction obtained through differential centrifugation followed by a sucrose gradient. This preparation yielded a 10-fold enrichment of activity over homogenate. Methionine uptake was found to be into an osmotically active space. A binding constant of 75.4 pmol/mg membrane protein was determined. A significant (p<.05) sodium stimulation of methionine uptake was observed. This indicated active (energy-dependent) transport in addition to the diffusive component of intravesicular mention accumulation. Decreasing the pH of buffer medium significantly (p<.05) depresses methionine transport. A Km = .114 mM and VMAX = 56.5 pmol/s/mg membrane protein were ascertained for methionine.