Lipoprotein Lipase: Modification of Its Kinetic Properties by Mild Tryptic Digestion

Content Provider	Scilit
Author	Bengtsson, Gunilla Olivecrona, Thomas
Copyright Year	1981
Description	Journal: Journal of Biological Inorganic Chemistry Mild tryptic digestion of lipoprotein lipase cleaved its polypeptide chain in the middle, but the pieces were held together by disulphide bonds. The modified enzyme retained its ability to bind to heparin and to anionic detergents and on gel filtration it eluted in a similar position as the native enzyme does. It also retained essentially full activity against soluble substrates. Thus, the overall physico-chemical properties of the enzyme were not markedly changed and its active site remained intact after treatment with trypsin. The activity of the modified enzyme against long-chain acylglycerols and phospholipids was, however, much reduced. With some emulsions, the decreased activity could be ascribed in part to a decreased ability of the modified enzyme to bind to the emulsion droplets. Under these conditions apolipoprotein CII partially restored both binding and activity. With a lysophosphatidylcholine-triacylglycerol emulsion the modified enzyme adsorbed almost completely to the emulsion droplets, but its activity was nonetheless very low. Thus, tryptic cleavage interfered with the ability of the enzyme to become properly orientated at the interface. With this emulsion apolipoprotein CII enhanced the activity of the native enzyme fourfold but the activity of the trypsin-treated enzyme 30-fold, so that the activity of the modified enzyme became almost as high as that of the native enzyme. It is concluded that apolipoprotein CII enhances the activity of lipoprotein lipase by stabilizing an effective orientation/conformation of the enzyme at the interface. This effect became more marked when the ability of the enzyme itself to attain this form had been reduced by tryptic cleavage.
Related Links	http://onlinelibrary.wiley.com/doi/10.1111/j.1432-1033.1981.tb05097.x/pdf
Ending Page	554
Page Count	8
Starting Page	547
ISSN	09498257
e-ISSN	14321327
DOI	10.1111/j.1432-1033.1981.tb05097.x
Journal	Journal of Biological Inorganic Chemistry
Issue Number	3
Volume Number	113
Language	English
Publisher	Wiley-Blackwell
Publisher Date	1981-01-01
Access Restriction	Open
Subject Keyword	Journal: Journal of Biological Inorganic Chemistry Lipoprotein Lipase
Content Type	Text
Resource Type	Article
Subject	Biochemistry Inorganic Chemistry