Ectoine-mediated protection of enzyme from the effect of pH and temperature stress: a study using Bacillus halodurans xylanase as a model

Abstract

Compatible solutes are small, soluble organic compounds that have the ability to stabilise proteins against various stress conditions. In this study, the protective effect of ectoines against pH stress is examined using a recombinant xylanase from Bacillus halodurans as a model. Ectoines improved the enzyme stability at low (4.5 and 5.0) and high pH (11 and 12); stabilisation effect of hydroxyectoine was superior to that of ectoine and trehalose. In the presence of hydroxyectoine, residual activity (after 10 h heating at 50 °C) increased from about 45 to 86 % at pH 5 and from 33 to 89 % at pH 12. When the xylanase was incubated at 65 °C for 5 h with 50 mM hydroxyectoine at pH 10, about 40 % of the original activity was retained while no residual activity was detected in the absence of additives or in the presence of ectoine or trehalose. The xylanase activity was slightly stimulated in the presence of 25 mM ectoines and then gradually decreased with increase in ectoines concentration. The thermal unfolding of the enzyme in the presence of the compatible solutes showed a modest increase in denaturation temperature but a larger increase in calorimetric enthalpy.

Hiding in Plain Sight: Mining Bacterial Species Records for Phenotypic Trait Information

“…For example, we found that KOs encoding synthesis of the osmoprotectant ectoine ( K06718 and K06720 ) were correlated with pH but not salinity optima ( Table 3 ). Recent work suggests that ectoine may have a role in stabilizing enzymes at extreme pH values ( 49 ). Our result indicates that pH homeostasis may be another role for ectoine in bacteria.…”

Biochemical Properties of Ectoine Hydroxylases from Extremophiles and Their Wider Taxonomic Distribution among Microorganisms

“…Since hydroxyectoine often possess function-preserving and stress-relieving properties superior to those of ectoine [29], [35]–[38], one wonders why not all ectoine producers synthesize 5-hydroxyectoine since this can readily be accomplished from ectoine in a single step [20]. Part of the answer to this question becomes apparent when one considers the physiological requirements and the oxygen dependence of the ectoine/hydroxyectoine producer microorganisms.…”

“…Despite their closely related chemical structures, 5-hydroxyectoine often possesses superior stress protecting and function preserving properties than its precursor molecule ectoine [29], [35]–[38]. Here, we focus on the ectoine hydroxylase, the enzyme that forms (4 S ,5 S )-2-methyl-5-hydroxy-1,4,5,6-tetrahydropyrimidine-4-carboxylic acid from the precursor ectoine through a region-selective and stereospecific hydroxylation reaction [13], [20].…”

Tinkering with Osmotically Controlled Transcription Allows Enhanced Production and Excretion of Ectoine and Hydroxyectoine from a Microbial Cell Factory

“…The very high salinity used to cultivate the ectoine/hydroxyectoine producer organism H. elongata in the established industrial production process is harsh on the fermentation and downstream processing equipment (32). Therefore, there has been considerable interest in developing alternative fermentation processes (54,55), in exploiting additional natural ectoine/hydroxyectoine producers (56, 57) (including a bacterium that secrets them naturally into the medium [58]), and in engineering natural and synthetic microbial production hosts for enhanced recovery of these high-value compounds (1,32). With respect to the latter approaches, ectoine/hydroxyectoine biosynthetic genes have been cloned into plasmids under the transcriptional control of either natural ect or synthetic promoters and transferred to Escherichia coli or Corynebacterium glutamicum host strains (59)(60)(61)(62) or integrated into the chromosomes of biotechnological workhorses such as C. glutamicum (63) or the methylotrophic yeast Hansenula polymorpha (64).…”