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Lipid-dependent membrane enzymes. Kinetic modelling of the activation of protein kinase C by phosphatidylserine.

Biochim. Biophys. Acta-Biomembr. 1069, 235-240 (1991)
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A previously developed kinetic theory for lipid-dependent membrane enzymes (Sandermann, H. (1982) Eur. J. Biochem. 127, 123-138) is used to examine the activation of protein kinase C by phosphatidylserine. Hill-coefficients ranging up to 11 have been reported for activation in mixed micelles with Triton X-100. On the basis of this uniquely high degree of cooperativity, protein kinase C has been postulated to represent a new class of lipid-dependent membrane enzymes (Newton, A. and Koshland, D.E., Jr. (1989) J. Biol. Chem. 264, 14909-14915). In contrast, activation in the absence of Triton X-100 has led to Hill-coefficients of only ≤ 2.6. In order to resolve the apparent discrepancy, activation is now considered to involve binding of PS monomers to interacting sites on the enzyme, a non-activating PS trapping process also occurring in the presence of Triton X-100. Estimates for trapping are made for several sets of published data for micellar activation. The kinetic model developed here successfully fits each data set using a Hill-coefficient of only 3.0. An influence of Ca2+/ions or of a two-step mechanism of lipid-protein interaction are considered as possible molecular explanations. It is concluded (i) that lipid activation of protein kinase C may proceed without unique cooperativity and (ii) that ligand trapping could provide another means for 'threshold-type' kinetic regulation of membrane enzyme and receptor systems.
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Publication type Article: Journal article
Document type Scientific Article
Keywords Activation ; Hill Coefficient ; Kinetic Model ; Ligand Trapping ; Lipid Regulation ; Phosphatidylserine ; Protein Kinase C
ISSN (print) / ISBN 0005-2736
e-ISSN 1879-2642
Quellenangaben Volume: 1069, Issue: 2, Pages: 235-240 Article Number: , Supplement: ,
Publisher Elsevier
Reviewing status Peer reviewed