Developmental change in human intestinal alkaline phosphatase.

Starch gel electrophoresis and inhibition studies with L-phenylalanine, L-homoarginine, L-leucine, L-leucylglycylglycine, and L-phenylalanylglycylglycine were carried out on a series of human alkaline phosphatases [orthophosphoric-monoester phosphohydrolase (alkaline optimum); EC 3.1.3.1] derived from fetal and adult liver, kidney, bone, and intestine. No differences between adult and fetal liver, kidney, or bone alkaline phosphatases were observed by either electrophoretic or inhibition studies. However, the fetal intestinal enzyme could be clearly distinguished from the adult intestinal enzyme by its greater anodal electrophoretic mobility and its retardation after treatment with neuraminidase. Even after extensive neuraminidase treatment, its anodal mobility was still slightly greater than that of adult intestinal alkaline phosphatase. Fetal and adult intestinal enzymes showed the same inhibition profiles with the series of inhibitors both before and after treatment with neuraminidase. A survey of intestinal samples from fetuses and premature infants of various gestational ages indicated that the changeover from the synthesis of fetal to adult intestinal enzyme begins at about 28-32 weeks of gestation. The difference between the fetal and adult forms of intestinal alkaline phosphatase may represent the expression of different gene loci or a difference in post-translational modification.