Effect of diet on enzymes of the brush border of the small intestine and kidney of rats

Abstract

The effect of diets containing various amounts of casein and starch on enzymes bound to the brush border of the small intestine and kidney of rats were investigated with the following results. 1) Diets with low starch and high casein contents resulted in higher specific activity of leucineaminopeptidase in the small intestine than diets with high starch and low casein contents. Diets with high starch and low casein contents increased the specific activity of maltase. 2) Rat small intestine contains at least two isoenzymes of leucineaminopeptidase: one bound to the brush border and the other not bound to it but recoverable in the soluble fraction. Only the former was influenced by the diet. 3) The maximum velocity (Vmax) of leucineaminopeptidase bound to the brush border was twice as much in rats on a high casein diet as in those on a low casein diet, but the Michaelis constant (Km) was approximately the same in both groups of rats. 4) Leucineaminopeptidase and maltase activities in the kidney were not influenced by diet.