Factors that cause the beta-anomeric preference of Na+/glucose cotransporter for intestinal transport of monosaccharide conjugates.
The intestinal transport of glucose- and galactose-conjugated acetaminophen (APAP glycoside) by Na+/glucose cotransporter (SGLT1) was studied. SGLT1-mediated transport of APAP glycosides preferred glucoside>galactoside and beta-anomer>alpha-anomer. These preferences agree with previous studies. NMR spectroscopic and molecular modeling studies indicated that the conformation of the glucose ring of alpha- and beta-glucosides of APAP, as well as glycosides in previous studies, is in the 4C1 chair form, the same form as glucose itself. Molecular dynamics analysis also indicated that the glucose ring was in the 4C1 chair form, and that there are differences between the rotational spaces of aglycones and hydroxy groups of glucose moieties between anomers. Therefore, we conclude that the beta-anomeric preference of glucose conjugate transport by SGLT1 is not due to the conformation of the glucose ring, but to the configuration of the aglycone at C-1 of the monosaccharide moiety.