Studies of serum and tissue maltases in the rat.

Rat serum, kidney, and small bowel maltases were partially purified and chromatographed on columns of Sephadex G-200. Serum and kidney maltase migrated as early prominent peaks, whereas small bowel maltase separated into at least two and probably three peaks. No sucrase activity was present in either the serum or kidney peaks or in the first peak of small bowel maltase. The first maltase peak from small bowel and serum maltases had an optimal range of activity from pH 5.8 to 6.2. Kidney maltase activity was optimal at a narrow pH of 6.2. Heat inactivation studies suggested that at least two maltases were present in the chromatographic peaks of serum and kidney and in the first peak from small bowel. However, the velocity of inactivation of serum maltase differed from both kidney and small bowel maltases. Although serum, kidney, and some small bowel maltases may have similar chromatographic characteristics, the origin of serum maltase in the rat remains unclear.