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C Erlanson-Albertsson

Publications and source records attributed to C Erlanson-Albertsson.

78 records · Page 5Linked to original sources
PubMed1981

Importance of the N-terminal sequence in porcine pancreatic colipase.

Colipase exists in pancreatic juice in a pro-form which is activated by limited trypsin hydrolysis. During this activation, the N-terminal pentapeptide 1Val-Pro-Asp-Pro-5Arg is cleaved. The new N-terminal sequence formed, 6Gly-Ile-Ile-Ile-10Asn, contains three isoleucine residues. The importance of these for stimulating lipase activity has been investigated by successive Edman degradation of epsilon-acetimidolysine residues followed by limited trypsin hydrolysis. The epsilon-amidinated colipase obtained was fully active both with a phospholipid-covered triacylglycerol (Intralipid) and tributyrin as substrate. After removal of the three isoleucine residues, the activity of colipase was lost with Intralipid but not with tributyrin as substrate. The shortened colipases regained their Intralipid activity upon addition of long-chain fatty acids. The binding of colipase to lipase was not affected by removal of the isoleucine residues.

Amino Acid Sequence↗
PubMed1981

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.

Animals↗
PubMed1980

Measurement of the binding of colipase to a triacylglycerol substrate.

The binding between colipase and two triacylglycerol substrates, tributyrin and Intralipid, in the presence of bile salts have been determined quantitatively by a method based on equilibrium partition in an aqueous two-phase system. In the model proposed the triacylglycerol, in the form of spherical droplets covered with bile salt, is assumed to have a certain number of independent binding sites at the surface for colipase. The binding of colipase to tributyrin at pH 7.0 in the presence of 4 mM sodium taurodeoxycholate and 150 mM NaCl had a dissociation constant Kd = 3.3 . 10(-7) M; the concentration of binding sites was 1.2 . 10(-6) M in a 102 mM tributyrin emulsion. When tributyrin was dispersed in 1 mM and 12 mM sodium taurodeoxycholate the dissociation constant was somewhat higher, 6.3 . 10(-7) M and 6.0 . 10(-7) M, respectively. Thus the binding strength was optimal at 4 mM sodium taurodeoxycholate. At the same time the concentration of binding sites decreased from 4.1 . 10(-6) M for 1 mM sodium taurodeoxycholate to 1.4 . 10(-6) M for 12 mM sodium taurodeoxycholate. This indicated that at higher bile salt concentration the bile salt acted as non-competitive inhibitors on the binding of colipase to the substrate, thus binding to other sites than colipase to the substrate. The binding of colipase to Intralipid, an emulsion of a long-chain triacylglycerol stabilized with phosphatidylcholine and glycerol, was more complex with indications of several different binding sites with different affinity. The majority of these had a dissociation constant Kd = 1.2 . 10(-6) M in the presence of 4 mM sodium taurodeoxycholate and 150 mM. With each droplet having a diameter of 10(-4) cm, the number of binding sites on each droplet was determined to 1.96 . 10(5) and the average area available for each colipase molecule to 1600 A at saturation. Colipase on denaturation has a surface of 1320 A.

Animals↗