A Systematic Study of Effects of Non‐Ionic Detergents on Solubilization and Activity of Pig Kidney Adenylate Cyclase

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Abstract
The effects of 17 non‐ionic detergents on pig kidney plasma membrane adenylate cyclase were tested (digitonin; detergents from the Triton series: X45, X100, X102, X114, X165, X305, X405, N101; the Brij series: 35, 56, 96 and the Tween series: 20, 40, 60, 80, 85). Membranes (2.66 mg protein/ml) were treated with increasing amounts of detergent for 150 min at 0°C. The adenylate cyclase activities present in treated membranes and in their corresponding non‐sedimentable fractions were measured at 30°C. Only detergents having hydrophilic lipophilic balance values from 12 to 14 were effective solubilizing agents. For these detergents, the solubilization yield was dependent on their structure. When solubilized adenylate cyclase kept at 0°C was incubated at 30°C, the enzyme catalytic activity exponentially decreased towards an equilibrium value with a half‐time of 5 min. This temperature‐dependent adjustment of enzyme activity was reversible. Its magnitude was dependent on the detergent used. A more progressive but less pronounced effect was observed with non‐solubilizing detergents. The micellar form of detergent in the incubation medium was found to be responsible for the appearance of microheterogeneity in the population of solubilized enzyme molecules differing by the substrate accessibility. This effect was suppressed when reducing the detergent concentration in the incubation medium.