Optimizing the enzymatic synthesis of β-d-galactopyranosyl-d-xyloses for their use in the evaluation of lactase activity in vivo

Disaccharides 2-O-, 3-O-, and 4-O-β-d-galactopyranosyl-d-xyloses (2, 3, and 1, respectively) were obtained by β-galactosidase-catalyzed reactions for their use in the evaluation of intestinal lactase activity in vivo. Their administration to suckling rats followed by determination of the derived d-xylose in the urine and measurement of lactase activity in intestinal homogenates showed 1 to be the most suitable disaccharide for a potential test of the deficiency of intestinal lactase. The synthesis of 1 was further studied by evaluating the effect of different variables on the yield and regioselectivity of the enzymatic galactosylation, and the purification process was optimized.

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