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The role of Glu78 in the catalysis of the Bacillus subtilis chorismate mutase (BsCM) is investigated using target randomizing mutagenesis and genetic selection. Results, taken in conjunction with those of other mutagenesis studies, indicate that Glu78 and Arg90 complement charge separation in the transition state, thus contributing to the efficient catalysis of BsCM.

Kachri fruit, Cucumis trigonus Roxburghi, contains high protease activity and has been used as meat tenderizer in the Indian subcontinent. A 67 kDa serine protease from Kachri fruit was purified by DEAE-Sepharose and CM-Sepharose chromatography, whose optimum activity was at pH 11 and 70 degrees C. Its activity was strongly inhibited by PMSF, but not by EDTA, pepstatin, or cysteine protease inhibitors. The substrate specificity of the purified protease towards synthetic peptides was comparable to cucumisin, the first characterized subtilisin class plant protease from the sarcocarp of melon fruit (Cucumis melo). These characteristics, along with the N-terminal amino acid sequence, indicated that the isolated protease from Cucumis trigonus Roxburghi is a cucumisin homologue, which belongs to the serine protease family.