The biosynthesis of intestinal sucrase-isomaltase in human embryo is most likely controlled at the level of transcription.

Although sucrase-isomaltase appears in the small intestine at quite different stages of development in man as compared with most mammals, we find that in human embryo also the appearance of sucrase-isomaltase mRNA closely parallels that of sucrase and isomaltase activities, as we have previously found to be the case in baby rabbits. Also, in the proximal-distal gradient of human embryonic intestine (proximal small intestine greater than distal small intestine greater than colon) the levels of these enzyme activities and those of the corresponding mRNA correlate closely. Finally, glucocorticosteroid treatment of a human colon carcinoma cell line (Caco-2) in vitro or of baby rabbits in vivo leads to a parallel increase of both sucrase and isomaltase activities and of sucrase-isomaltase mRNA. We conclude that in man also, in spite of the different timing in development, the biosynthesis of sucrase-isomaltase is most likely to be controlled at the level of transcription or perhaps of the mRNA stability.