DETERGENT SOLUBILIZATION OF 3-BETA-HYDROXYSTEROID DEHYDROGENASE FROM DOG PANCREAS

Functional 3 beta-hydroxysteroid dehydrogenase coupled with isomerase (3 beta-HSD) was extracted from dog pancreatic mitochondria by treatme nt with the zwitterionic detergent CHAPSO. Increasing concentrations o f this detergent led to a progressive and simultaneous solubilization of the pregnene (C-21) and androstene (C-19) dehydrogenase activities. Optimal solubilization of both C-21 and C-19 3 beta-HSD activities wa s achieved at a detergent/protein ratio of 0.6 (w/w). One hundred thir ty percent of the initial particulate enzyme activities were recovered in the 105,000 g supernatant fluid with a 2.5-fold increase in the en zymatic specific activities. The C-21/C-19 activity ratios were 1.3 fo r mitochondria and 1.39 for the solubilized preparation. The apparent Km values for steroid substrates were unchanged after solubilization. Treatment of the mitochondrial suspension with sodium deoxycholate, CT AB, Lubrol XW, Brij 58, Emulgen 913 and Triton X-100 markedly decrease d the 3 beta-HSD activities as a function of the detergent concentrati on and failed in to achieve solubilization.