Antonowicz I, Lebenthal E
Gastroenterology. 1977 Jun;72(6):1299-303.
The concomitant appearance of enterokinase (EK) and trypsin activities in the human intestinal mucosa is indicative of the importance of EK as an activator of trypsinogen and therefore as the key enzyme in protein digestion. Enterokinase can be detected in fetal mucosa from the 26th week of gestation on, paralleling appearance of tryptic activity in meconium. The developmental pattern of EK activity increases with age. Between 26 to 30 weeks of gestation, the EK activity is only 6% and full term babies (40 weeks) 20% of that found in older children. In contrast, lactase studies during development show a lactase activity of only 30% in human fetuses between 26 to 34 weeks of gestation as compared to full term babies. During the same gestational period, sucrase and maltase activities reach 70% of the full term. In addition, the distributional pattern of EK differs from the disaccharidases, showing the highest activity in duodenum and the lowest in ileum, whereas disaccharidases are highest in jejunum with lower activity in duodenum and ileum. Differences in topographical distribution and time of appearance of EK and disaccharidases may be attributed to differences in orgin as well as subcellular localization of these enzymes. It is conceivable that the premature infant, between 26 to 30 weeks of gestation, is better equipped to deal with hydrolysis of alpha-glucosides than of lactose.
人肠黏膜中肠激酶（EK）和胰蛋白酶活性的同时出现表明，EK作为胰蛋白酶原激活剂具有重要意义，因此是蛋白质消化中的关键酶。从妊娠第26周起即可在胎儿黏膜中检测到肠激酶，同时胎粪中也出现胰蛋白酶活性。EK活性的发育模式随年龄增长而增加。在妊娠26至30周之间，EK活性仅为大龄儿童的6%，足月婴儿（40周）为20%。相比之下，发育过程中的乳糖酶研究表明，妊娠26至34周的人类胎儿乳糖酶活性仅为足月婴儿的30%。在同一妊娠期，蔗糖酶和麦芽糖酶活性达到足月时的70%。此外，EK的分布模式与双糖酶不同，在十二指肠中活性最高，在回肠中最低，而双糖酶在空肠中活性最高，在十二指肠和回肠中活性较低。EK和双糖酶在拓扑分布和出现时间上的差异可能归因于这些酶的来源以及亚细胞定位的差异。可以想象，妊娠26至30周的早产儿更有能力处理α-糖苷的水解，而不是乳糖的水解。
