Acetyl esterase in Bacillus cereus spores

Direct measurement of acetylesterase in living protist cells

The fluorogenic acetylesterase (acetic ester hydrolase EC 3.1.1.6.) substrate, fluorescein diacetate, was used to measure enzyme activity in living protist cells. The visual enzyme assay was done by monitoring fluorochromasia by fluorescent microscopy. Quantitative fluorogenic assays were done by measuring the evolved fluorescein in a fluorometer. Of 59 strains of bacteria, 35 were fluorochromatically positive. Eight of the fluorochromatically negative strains were fluorogenically positive. Of 22 strains of slime molds and fungi, all were fluorochromatically positive. Three out of 12 different algae were fluorochromatically positive. Several unidentified protozoa were also fluorochromatically positive. Four out of six protozoa were fluorochromatically positive. Structures of special interest showing acetylesterase activity were: the growing hyphal tips of fungi, the vacuolated areas of yeast and protozoa, newly formed bacterial spores or immature fungal spores, "mesosome-like" bodies in Bacillus megaterium, and the cell membrane and nuclear region of green algae. Yeast protoplasts and bacterial protoplasts and spheroplasts were fluorochromatically positive when derived from positive cells and negative when derived from negative cells. There was no correlation between the possession of a capsule and acetylesterase activity. There was no effect on the viability of bacterial cells incubated in the presence of fluorescein diacetate. Paraoxon inhibited bacterial and yeast enzyme at 10(-5)m. Eserine (10(-5)m) and Paraoxon (10(-7)m) inhibited B. megaterium enzyme. Sodium acetate at 10(-2)m did not inhibit bacterial enzyme. The implications of these findings on the location and expression of esterase activity in living cells are discussed.

Dissociatiion of esterase from proteinase activity of Bacillus subtilis spores

Preparations of ballistically disintegrated Bacillus subtilis spores have been shown to possess proteinase in addition to esterase activities. Both proteinase and esterase activities have been suggested as trigger for the initiation of germination, but information on these two activities in bacterial endospores is scant. Since some proteinases catalyze the hydrolysis of esters, there exists a possible identity of some esterases with proteinases. To get information on the esterase and proteinase activities of B. subtilis spores, the sensitivity to heat and to inhibitors was explored. The thermal effect and the effect of certain inhibitors on esterase activities towards several esters suggested that an unspecific esterase was responsible for these activities.Differential effects of heat, pH, and inhibitors on esterase and proteinase activities indicated the dual nature of these two activities. In absence of convincing experimental evidence to the contrary, the present indication seems to be that the esterase activities observed in B. subtilis spores were dissociated from the activity which hydrolyzes casein. The esterase activity was readily inhibited by diethyl p-nitrophenyl phosphate, diisopropylphosphofluoridate, eserine, sodium fluoride, and Zn ions, and possessed properties of a B-esterase. The proteinase activity was inhibited only by diisopropylphosphofluoridate showing properties, so far studied, similar to subtilopeptidase.