Purification and characterization of two novel proteolytic enzymes in membranes of Escherichia coli. Protease IV and protease V.

MI06Escherichia coli cells contain two membrane-bound esterases, one of which is localized in both inner and outer membranes and the other present only in the inner membrane (Pacaud, M. (1982) J. Bacteriol.149, in press).These two enzymes have been purified to homogeneity and shown to be capable of hydrolyzing a mixture of E. coli proteins.The inner membrane esterase has been called protease N ; the other esterase has been designated protease V. Protease N migrates as a single band on sodium dodecyl sulfate gels with an apparent Mr = 34,000.However, this enzyme displays an apparent M, = 660,000 on Ultrogel columns in the presence of Emulphogen BC-720.The large difference in size of the native enzyme appears to be due to its association with the detergent.The molecular weight of protease V could not be determined because of the interactions of this enzyme with detergents.Protease