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Increase of latent HMG‐COA reductase activity with increasing density of cell cultures
Author(s) -
Chen Harry W.
Publication year - 1983
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041170117
Subject(s) - hmg coa reductase , reductase , hydroxymethylglutaryl coa reductase inhibitors , chemistry , cell , biochemistry , enzyme , biology , cholesterol
The total (active plus latent) activity of HMG‐CoA reductase declined linearly with increasing cell density in cultures of three lines of mammalian cells. The active form disappeared almost entirely under this condition, while the latent (presumably phosphorylated) form increased to some extent. The disappearance of active HMG‐CoA reductase with concomitant increase in the proportion of latent HMG‐CoA reductase was correlated with the decline in cellular multiplication and sterol synthesis. These results suggest that interconversion of HMG‐CoA reductase between active and inactive forms through phospho‐rylation‐dephosphorylation can be associated with changes in the rate of cellular proliferation in cell cultures. However, the decreased rate of sterol synthesis followed more closely the slower disappearance of the total HMG‐CoA reductase activity than the rapid decrease of the active form of the reductase alone. Therefore, changes in the rate of cellular proliferation can affect the interconversion of HMG‐CoA reductase between active and inactive forms through reversible phosphorylation. However, phosphorylation of the enzyme to the inactive form appears not to be the mechanism by which the sterol synthetic rate is regulated in confluent cell cultures. Rather, the amount of total HMG‐CoA reductase determines the rate of sterol synthesis.