Freund J N, Duluc I, Foltzer-Jourdainne C, Gosse F, Raul F
Institut National de la Santé et de la Recherche Médicale, Unité 61, Strasbourg, France.
Biochem J. 1990 May 15;268(1):99-103. doi: 10.1042/bj2680099.
The expression of lactase was compared in the jejunum and colon of the rat at the levels of enzyme activity and protein and RNA content. We found that the enzyme proteins and the corresponding mRNAs share common features and are encoded by a single gene in both intestinal segments. In the jejunum, large amounts of lactase mRNA and proteins were detected during postnatal development as well as in adult rats, despite the 10-fold decline in lactase specific activity which occurs at weaning. In contrast, in the colon the expression of lactase was restricted to early postnatal development. In the colon, the enzymic activity of lactase and the amounts of protein and mRNA followed parallel development profiles with a peak at day 4 after birth. Injections of thryoxine or epidermal growth factor into neonates led to small modifications in the expression of lactase in the jejunum. On the other hand, these treatments caused a large decline in lactase activity in the colon that paralleled a decrease in the amount of lactase protein and mRNA. These data indicate that the expression of lactase is mainly regulated at the post-transcriptional level in the jejunum, whereas it is controlled at the pretranslational level in the colon.
在大鼠的空肠和结肠中，对乳糖酶在酶活性、蛋白质及RNA含量水平上的表达进行了比较。我们发现，在两个肠段中，酶蛋白和相应的mRNA具有共同特征，且由单个基因编码。在空肠中，尽管断奶时乳糖酶比活性下降了10倍，但在出生后发育期间以及成年大鼠中均检测到大量乳糖酶mRNA和蛋白质。相反，在结肠中，乳糖酶的表达仅限于出生后早期发育阶段。在结肠中，乳糖酶的酶活性、蛋白质和mRNA的量呈现平行的发育曲线，在出生后第4天达到峰值。给新生大鼠注射甲状腺素或表皮生长因子，导致空肠中乳糖酶表达出现微小变化。另一方面，这些处理导致结肠中乳糖酶活性大幅下降，这与乳糖酶蛋白和mRNA量的减少相一致。这些数据表明，乳糖酶的表达在空肠中主要在转录后水平受到调控，而在结肠中则在翻译前水平受到控制。
