Feeding status affects in vivo prosucrase.isomaltase processing in rat jejunum

J Nutr. 1992 Mar;122(3):528-34. doi: 10.1093/jn/122.3.528.


Fed and fasted (18 h) adult male rats received a primed constant infusion of [3H]leucine for 15 to 180 min. Prosucrase-isomaltase (pro-SI) and sucrase were isolated from mixed jejunal mucosal membranes by immunoprecipitation and separated from one another by polyacrylamide gel electrophoresis under denaturing and reducing conditions. The rate at which pro-SI was processed to sucrase was calculated on the assumption that the steady-state specific radioactivity of leucine in pro-SI defined the pool of amino acids used in the formation of brush border sucrase. At isotopic steady state, pro-SI achieved a specific radioactivity that was higher than that of mucosal free leucine in both feeding groups. The relationship between the isotopic equilibrium of the free amino acid pools and pro-SI was sensitive to feeding status; the specific radioactivity of pro-SI was 25 and 55% (P less than 0.05) of the blood specific radioactivity in fed and fasted animals, respectively. The fractional rate of pro-SI processing tended to be higher (P less than 0.07) in fed (407%/d) than in fasted animals (274%/d). We conclude that the general mucosal free amino acid pool is not the amino acid pool from which pro-SI is synthesized and that the rate of pro-SI processing from the endoplasmic reticulum-Golgi membranes to the brush border membrane is sensitive to the feeding status of the animal.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acids / analysis
  • Amino Acids / blood
  • Animals
  • Densitometry
  • Electrophoresis, Polyacrylamide Gel
  • Enzyme Precursors / isolation & purification
  • Enzyme Precursors / metabolism*
  • Intestinal Mucosa / chemistry
  • Jejunum / enzymology*
  • Male
  • Microvilli / enzymology
  • Oligo-1,6-Glucosidase / isolation & purification
  • Oligo-1,6-Glucosidase / metabolism*
  • Precipitin Tests
  • Rats
  • Sucrase / isolation & purification
  • Sucrase / metabolism*


  • Amino Acids
  • Enzyme Precursors
  • Oligo-1,6-Glucosidase
  • Sucrase