INTERACTION OF ALPHA-2-MACROGLOBULIN WITH ALKALINE PROTEINASE FROM ANALKALOPHILIC BACILLUS SP GROWN IN AN EXTRAORDINARILY ALKALINE ENVIRONMENT

The interaction of alpha2-macroglobulin (alpha2M) with an alkaline ser ine proteinase (ALPase 1) from alkalophilic Bacillus sp. grown in an e xtraordinarily alkaline environment was investigated. Stoichiometry of the reaction showed that ALPase I bound to alpha2M in a molar ratio o f about 2:1. The alpha2M-ALPase I complex showed about 80% of the prot einase activity shown by ALPase I in the hydrolysis of -L-prolyl-L-phe nylalanyl-4-methyl-coumaryl-7-amide (Suc-Ala-Ala-Pro-Phe-MCA) and case in. The conformational changes in the alpha2M molecule caused by the c omplex formation at pH 7.5 were determined from electron micrographs a nd difference spectra. The antigenic activity of the alpha2M-ALPase I complex with the anti-ALPase I antiserum was found to be completely ab olished. Immunoelectrophoresis of the complex incubated at pH 7.5 afte r 48 h showed no appreciable change, and the complex was recognized as exhibiting enhanced stability at pH 7.5.