Solubilization and Resolution of Thromboxane Synthesizing System from Microsomes of Bovine Blood Platelets

The thromboxane synthetase system of the microsomes of bovine blood platelets was solubilized by the treatment with Triton X-100. The solubilized preparation was separated into two enzyme fractions by DEAE-cellulose chromatography. One catalyzed the formation of prostaglandin H2 from arachidonic acid in the presence of heme and tryptophan. The other fraction converted prostaglandin H2 to thromboxane B2 and 12L-hydroxy-5,8,10-heptadecatrienoic acid. However, incubation of the latter fraction with prostaglandin H2 at lower temperature produced an unstable compound with platelet-aggregating activity, which was presumably thromboxane A2 and which decomposed readily to thromboxane B2 and 12L-hydroxy-5,8,10-heptadecatrienoic acid.