Related Experiment Video
Updated: Aug 19, 2026

Cholesterol Efflux Assay
Published on: March 6, 2012
Modulation of reconstituted cholesterol 7 alpha-hydroxylase by phosphatase and protein kinase
Abstract:
Cholesterol 7 alpha-hydroxylase activity was completely inhibited by incubation with alkaline phosphatase in a reconstituted enzyme system containing a cytochrome P-450, NADPH-cytochrome P-450 reductase and phospholipid. On the other hand, cAMP-dependent protein kinase stimulated cholesterol 7 alpha-hydroxylase activity by 2.5-fold. The modulation of cholesterol 7 alpha-hydroxylase activity was dependent on the amount of phosphatase or kinase added. The phosphatase inhibited enzyme activity was partially reversed by the treatment with protein kinase. These experiments indicate that the reconstituted cholesterol 7 alpha-hydroxylase activity is reversibly regulated by phosphorylation/dephosphorylation mechanism.
More Related Videos
Related Concept Videos
Phosphorylation
During phosphorylation, protein kinases transfer the terminal phosphate group of ATP to specific amino acid side chains of substrate proteins. Serine, threonine, and tyrosine are the most commonly...
Protein Kinases and Phosphatases
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...
Overview of Fatty Acid Metabolism
Fatty acids are catabolized in a process called beta-oxidation, which takes place in the matrix of the mitochondria and converts their fatty acid chains into two-carbon units of acetyl groups. The acetyl...
Synthesis of Phosphatidylcholine in the ER Membrane
The major components of all eukaryotic cell...
Amplifying Signals via Enzymatic Cascade
Calmodulin-dependent Signaling
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...

