The identity and properties of two forms of activated colipase from porcine pancreas.
Colipase is excreted as a procolipase, colipase101. It is activated by low concentrations of trypsin, hydrolyzing the N-terminal pentapeptide. With higher concentrations of trypsin or in the presence of Ca2+ a smaller form of colipase containing 85 amino acids, appears. It has glycine as the N-terminal and arginine as the C-terminal amino acid residue and has lost 11 amino acids in the C-terminal chain. The ability of colipase85 to activate lipase with tributyrin as substrate is about the same as for colipase96 and procolipase. With fenfluramine, an anoretic agent, added to the tributyrin colipase assay system, the specific activities of colipase96 and colipase85 are similar and about five times higher than that of colipase101. With intralipid as substrate colipase85 enables lipase to reach the triacylglycerol substrate more rapidly than colipase96, having about six times shorter lagtime for a given concentration. Colipase84, obtained by splitting off the C-terminal arginine from colipase85, has a lagtime somewhere between colipase85 and colipase96, pointing to the importance of arginine85 for Intralipid activity. The binding between lipase and colipase has about the same strength for procolipase, colipase96 and for colipase85, Kd being about 10(-6) M either in buffer or in the presence of 2 mM taurodeoxycholate at pH 7. Addition of long chain fatty acids in the presence of bile salts increases the binding strength between colipase and lipase 100-fold, both for colipase96 and colipase85.
D000818:Animals; D001120:Arginine; D003089:Colipases / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005217:Fat Emulsions, Intravenous / Q000378:metabolism; D005277:Fenfluramine / Q000494:pharmacology; D008049:Lipase / Q000378:metabolism; D010179:Pancreas / Q000032:analysis*; D011506:Proteins / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013552:Swine; D014280:Triglycerides / Q000378:metabolism; D014357:Trypsin
D003089:Colipases; D005217:Fat Emulsions, Intravenous; D011506:Proteins; D014280:Triglycerides; D005277:Fenfluramine; D001120:Arginine; D008049:Lipase; D014357:Trypsin; C005830:tributyrin