Studies on ali-esterases. 5. Substrate specificity of the esterases of some saprophytic mycobacteria

Abstract

Mycobacterium tuberculosis H37RV, M. phlei and 5 other strains of mycobacteria isolated from human stomach washings were grown in bouillon, Dubos medium, Proskauer and Beck, and Lowenstein medium. The medium of Proskauer and Beck was most convenient for culturing large amounts of mycobacteria. Growth of some strains was inhibited by 10-5 [image] diethyl p-nitrophenyl phosphate and 3 x 10-6 [image] diisopropyl p-nitrophenyl phosphate whereas growth of other strains was not affected under the same conditions. The ali-esterase activity of the washed and resuspended bacteria, rat brain, and rat liver homogenates was measured in the Warburg apparatus. Esterases of the 8 strains of bacteria as well as those of rat brain and rat liver differed in their substrate specificities towards tributyrin, tripropionin triacetin, phenyl propionate, phenyl butyrate, phenyl acetate, ethyl butyrate, ethyl [beta]-phenylpropionate, ethylphenylacetate, ethyl benzoate, ethylleucine, ethyl-[beta]-phenylalamine butyranilide and acetanilide and in their degree of inhibition by diethyl p-nitrophenyl phosphate, diisopropyl p-nitrophenyl phosphate and phenyl N-n-propylcarbamate. It is suggested that these ali-esterases have a function in protein metabolism since they are capable of hydrolyzing amino acid esters and certain amides.