Developmental changeover in rat duodenal alkaline phosphatase.

The specific activity of alkaline phosphatase in the rat duodenum increased just prior to birth, leveled off and then increased again at about 20 days after birth. During the postnatal rise in activity the electrophoretic pattern of the enzyme on sodium dodecyl sulphate (SDS) polyacrylamide gels changed from a single activity band to three bands. The changed pattern was identical with that of the adult duodenal enzyme. The fetal- and adult-type enzymes had different sensitivities to neuraminidase, suggesting that there is a significant difference in the sialic acid content of these two forms. This molecular conversion may be necessary for adaptation to eating a solid food diet, because it occurs just before the weaning period.