The partitioning of commercial COX from Nocardia erythropolis and Pseudomonas sp. has been shown to depend on the detergent partitioning, since factors that affected the Triton X-114 distribution, such as temperature of partitioning, pH and phosphate concentration of the buffers, affected in the same way the distribution of enzyme [16]. Thus our results are in agreement with those findings. The reason for the different behavior of the detergent packing in cell extracts and in broth may lie in the fact that detergent partitioning is affected by physicochemical factors such as the presence of polyols, lipids, surfactants, etc [13], which can be present in cell extracts but not in the cell culture.