Abstract
Human plasma apolipoproteins apoA-I, A-II, C-I, C-II and C-III (with the exception of apoE), porcine pancreatic colipase and procolipase hydrolyze 4-methylumbelliferyloleate. In all cases, liberation of 4-methylumbelliferone could be inhibited by phenylmethylsulfonylfluoride, thus suggesting the involvement of serine residues. To the best of our knowledge this is the first report on the esterase activities of these peptides. Synthetic fragments of the lipoprotein lipase activator, apoC-II, prepared according to the known sequence, also possessed this esterase-type of activity. Furthermore, the esterase-type of activities of the synthetic apoC-II fragments with different chain lengths bore a relatively good correlation to the reported abilities to these peptides to produce activation of lipoprotein lipase. We propose a model for the mechanism of activation of lipoprotein lipase by apolipoprotein C-II. ApoC-II would enhance the apparent catalytic rate constant of lipoprotein lipase by functioning as a specific acyl-enzyme hydrolase. A similar catalytic mechanism is suggested for other protein co-factors of hydrolytic enzymes.
Original language | English (US) |
---|---|
Pages (from-to) | 21-32 |
Number of pages | 12 |
Journal | Chemistry and Physics of Lipids |
Volume | 33 |
Issue number | 1 |
DOIs | |
State | Published - Jul 1983 |
Keywords
- apolipoproteins
- esterases
- lipoprotein lipase
- phenylmethylsulfonylfluoride
- protein co-factors
ASJC Scopus subject areas
- Biochemistry
- Molecular Biology
- Organic Chemistry
- Cell Biology