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Phosphoenolpyruvate Carboxykinase of Rat Small Intestine: Distribution and Regulation of Activity and mRNA Levels¹

Division of Nutritional Sciences and Section of Biochemistry, Molecular and Cell Biology of the Division of Biological Sciences, Savage Hall, Cornell University, Ithaca, NY 14853

Phosphoenolpyruvate carboxykinase (PEPCK) activity is present along the length of rat small intestine and in enterocytes throughout the villus-crypt axis. There is no detectable activity in submucosal layers. Messenger RNA encoding PEPCK is detectable in rat intestinal mucosa and the relative abundance increases markedly (3- to 8-fold) during starvation or streptozotocin-diabetes. However, these changes are not matched by changes in enzyme activity which are only slightly increased (1.5-fold). The intestine of neonatal rats possesses relatively high amounts of both PEPCK activity and mRNA. Based on the distribution and regulation of intestinal PEPCK, it is proposed that the enzyme does not play a significant role in either gluconeogenesis or glutamine catabolism in adult rats.

KEY WORDS: • phosphoenolpyruvate carboxykinase • intestine • rat • gluconeogenesis

¹ This work was supported in part by N.I.H. grant AM 32894.

Manuscript received 25 August 1988. Revision accepted 14 November 1988.