Site--site interaction in the lipid activation of beta-hydroxybutyrate dehydrogenase

Kinetic data for the activation of the beta-hydroxybutyrate dehydrogenase by long-chain lecithins [(1979) Biochemistry 18, 2420-2429; (1983) J. Biol. Chem. 258, 208-214] are analyzed. A previous kinetic model [(1982) Biochemistry 21, 3899-3908] is shown not to apply. Instead, the use of a two-site Adair equation points to a strongly cooperative interaction between the lecithin binding sites (delta G, -2.8 kcal/mol).