Article ID Journal Published Year Pages File Type
1937634 Biochemical and Biophysical Research Communications 2007 6 Pages PDF
Abstract
Assay conditions for the 11β-hydroxysteroid dehydrogenase have been optimized by adding phospholipids in the media buffer to increase and stabilize the enzymatic activity. The presence of phospholipids greatly facilitates the study of the binding of cortisone and NADPH at the enzyme catalytic site. Kinetic analyses conducted with the human and rabbit enzyme isoforms suggest that both enzymes behave according to an ordered sequential bi-bi mechanism where the NADPH is the first to bind at the active site followed by cortisone. The equilibrium dissociation constant, Kia as well as the apparent Michaelis-Menten constants Kma, Kmb, kcata, and kcatb for NADPH and cortisone, have been determined to be 147.5 μM, 14.4 μM, 43.8 nM, 0.21 min−1, and 0.27 min−1, respectively, for the human enzyme and 41.1 μM, 3.1 μM, 161.7 nM, 0.49 min−1, and 0.52 min−1, respectively, for the rabbit enzyme.
Related Topics
Life Sciences Biochemistry, Genetics and Molecular Biology Biochemistry
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