TABLE 7

Ontogeny of selected intestinal brush border hydrolases

A specific comparison of lactase and sucrase is most discriminating in activity between neonates and adults, and across species in the neonatal period. Summarizes composite information derived from RNA expression, protein expression, and/or enzyme activity.

EnzymeHumanRatPigOther
Lactase-phorizin hydrolasePresent and functional at birth;  typically declines after  weaning, but variable in  different populations  (Montgomery et al., 1991)Transcribed from birth in jejunum with  transient expression in ileum and  colon (Freund et al., 1990)Present in late gestation and active  at birth but activity decreases in  second postnatal week (Shulman et al., 1988; Tivey et al.,  1994; Buddington and Malo,  1996; Wang and Xu, 1996;  Burrin et al., 2001)Low at birth with subsequent  increase in dogs  (Buddington et al., 2003)
Rapid increase in activity in jejunum  and colon during 1st week  postnatally, with subsequent decline  at weaning (Henning, 1981; Foltzer- Jourdainne and Raul, 1990)
Sucrase-isomaltase complexSynthesized as pro-form in utero,  but not functional until  approximately GW 26; also  transiently expressed in colon  of neonates (Triadou and  Zweibaum, 1985)RNA not detected in neonates; Activity  low or not detected until PND 14 in  small intestine, but increases rapidly  through weaning (PND 21);  transiently expressed in colon near  weaning (Henning, 1981; Toofanian,  1984; Foltzer-Jourdainne et al.,  1989; Galand, 1989; Freund et al.,  1990; Leeper and Henning, 1990)Present at birth with increase in  activity during second postnatal  week (James et al., 1987;  Shulman et al., 1988; Smith,  1988)Present at birth in dogs but not  rabbits; increased activity  at weaning (Galand, 1989)