23] β-methylaspartate-glutamate mutase from Clostridium tetanomorphum

Abstract

Publisher Summary This chapter provides an overview of β-methylaspartate-glutamate mutase from Clostridium tetanomorphum. The conversion of L-glutamate to threo-30-methyl-L-aspartate by glutamate mutase is the initial reaction in the anaerobic degradation of glutamate by Clostridium tetanomorphum and other Clostridium species. Two readily separable proteins called component E (MW 128,000) and component S (MW 17,000), a cobamide coenzyme and a sulfhydryl compound, are required for activity. Component S is reversibly inactivated by oxygen and, therefore, must be reduced by a sulfhydryl compound for full activity. Two assay methods are described in the chapter: a spectrophotometric assay done in the presence of air and an anaerobic assay. The spectrophotometric assay, which is generally used for estimating mutase activity, is based on the conversion of glutamate to mesaconate by the coupled action of mutase and β-methylaspartase. The anaerobic assay is based upon the conversion of β-methylaspartate to glutamate and is applicable only to purified mutase preparations in which β-methylaspartase is either absent or fully inhibited by Ca 2+ .