Pancreatic lipase-colipase binds strongly to the thylakoid membrane surface.
BACKGROUND
Isolated thylakoid membranes, i.e. the photosynthetic membranes of green leaves, inhibit the activity of pancreatic lipase and colipase during hydrolysis of fat in vitro. This inhibition has been demonstrated to cause reduced food intake and improved hormonal and lipid profile in vivo. One of the reasons suggested for the inhibiting effect is binding of lipase-colipase to the thylakoid membrane surface. This prompted a study of the binding of lipase and colipase to thylakoids.


RESULTS
The results showed that lipase and colipase strongly bind to the thylakoid membrane surface. The dissociation constant was determined at 1.2 × 10⁻⁸  mol L⁻¹; binding decreased after treatment of thylakoids with pepsin/trypsin to 1.0 × 10⁻⁷ and to 0.6 × 10⁻⁷  mol L⁻¹ after treatment with pancreatic juice. Similarly, delipidation of thylakoids caused a decrease in binding, the dissociation constant being 2.0 × 10⁻⁷  mol L⁻¹.


CONCLUSIONS
The binding of pancreatic lipase-colipase to the thylakoid membrane is strong and may explain the inhibition of lipase-colipase activity by thylakoids. After treatment with proteases to mimic intestinal digestion binding is decreased, but is still high enough to explain the observed metabolic effects of thylakoids in vivo.
Department of Biochemistry and Structural Biology, Chemical Centre, Lund University, SE-221 00, Lund, Sweden.
Sinan Cem
SC
Emek
Hans-Erik
HE
Åkerlund
Charlotte
C
Erlanson-Albertsson
Per-Åke
PÅ
Albertsson
D000818:Animals; D003089:Colipases / Q000378:metabolism*; D004041:Dietary Fats / Q000032:analysis / Q000378:metabolism*; D004063:Digestion; D007700:Kinetics; D008049:Lipase / Q000378:metabolism*; D008055:Lipids / Q000032:analysis; D008954:Models, Biological; D010179:Pancreas / Q000201:enzymology*; D010189:Pancreatic Juice / Q000201:enzymology / Q000378:metabolism; D010434:Pepsin A / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D059748:Proteolysis; D012997:Solvents / Q000737:chemistry; D018724:Spinacia oleracea / Q000378:metabolism; D013499:Surface Properties; D034421:Sus scrofa; D020524:Thylakoids / Q000737:chemistry / Q000378:metabolism*; D014357:Trypsin / Q000378:metabolism
D003089:Colipases; D004041:Dietary Fats; D008055:Lipids; D012997:Solvents; D008049:Lipase; D014357:Trypsin; D010434:Pepsin A