Gene Cloning, Prokaryotic Expression, and Biochemical Characterization of a Soluble Trehalase in Helicoverpa armigera Hübner (Lepidoptera: Noctuidae)

Efficient production and characterization of a newly identified trehalase for inhibiting the formation of bacterial biofilms

Trehalase has attracted widespread attention in medicine, agriculture, food, and ethanol industry due to its ability to specifically degrade trehalose. Efficient expression of trehalase remains a challenge. In this study, a putative trehalase-encoding gene (Tre-zm) from Zunongwangia mangrovi was explored using gene-mining strategy and heterologously expressed in E. coli. Trehalase activity reached 3374 U·mL-1 after fermentation optimization. The scale-up fermentation in a 15 L fermenter was achieved with a trehalase production of 15,068 U·mL-1. The recombinant trehalase TreZM was purified and characterized. It displayed optimal activity at 35 °C and pH 8.5, with Mn2+, Sn2+, Na+, and Fe2+ promoting the activity. Notably, TreZM showed significant inhibition effect on biofilm forming of Staphylococcus epidermidis. The combination of TreZM with a low concentration of antibiotics could inhibit 70 % biofilm formation of Staphylococcus epidermidis and 28 % of Pseudomonas aeruginosa. Hence, this study provides a promising candidate for industrial production of trehalase and highlights its potential application to control harmful biofilms.

Validamycin Inhibits the Synthesis and Metabolism of Trehalose and Chitin in the Oriental Fruit Fly, Bactrocera dorsalis (Hendel)

The oriental fruit fly, Bactrocera dorsalis (Hendel), is a notorious invasive pest that has raised concerns worldwide. Validamycin has been demonstrated to be a very strong inhibitor against trehalase in a variety of organisms. However, whether validamycin can inhibit trehalase activity to suppress trehalose hydrolysis and affect any other relevant physiological pathways in B. dorsalis remains unknown. In this study, the effects of validamycin injection on the synthesis and metabolism of trehalose and chitin were evaluated. The results show that validamycin injection significantly affected trehalase activity and caused trehalose accumulation. In addition, the downstream pathways of trehalose hydrolysis, including the synthesis and metabolism of chitin, were also remarkably affected as the expressions of the key genes in these pathways were significantly regulated and the chitin contents were changed accordingly. Intriguingly, the upstream trehalose synthesis was also affected by validamycin injection due to the variations in the expression levels of key genes, especially BdTPPC1. Moreover, BdTPPC1 was predicted to have a binding affinity to validamycin, and the subsequent in vitro recombinant enzyme activity assay verified the inhibitory effect of validamycin on BdTPPC1 activity for the first time. These findings collectively indicate that validamycin can be considered as a promising potential insecticide for the management of B. dorsalis.

Purification and Functional Characterization of a Soluble Trehalase in Lissorhoptrus oryzophilus (Coleoptera: Curculionidae)

Trehalase is the only enzyme known for the irreversible splitting of trehalose and plays a major role in insect growth and development. In this report, we describe a basic study of the trehalase gene fragment encoding a soluble trehalase from Lissorhoptrus oryzophilus (LoTRE1). Sequence alignment and phylogenetic analysis suggested that LoTRE1 was similar to some known insect trehalases and belongs to the Coleoptera trehalase group. Additionally, LoTRE1 was expressed mainly in the fat body. Purified protein was obtained using heterologous expression of LoTRE1 in Escherichia coli, and the recombinant protein exhibited the ability to decompose trehalose. Enzyme-substrate docking indicated the potential involvement of other residues in the catalytic activity, in addition to Asp 333. Moreover, feeding of adults on LoTRE1 dsRNA silenced the transcription of LoTRE1 and thereby reduced the activity of trehalase and increased the trehalose content; it also led to a 12% death rate. This study reveals essential molecular features of trehalase and offers insights into the structural aspects of this enzyme, which might be related to its function. Taken together, the findings demonstrate that LoTRE1 is indispensable for adults of this pest and provide a new target for the control of L. oryzophilus.

Purification and Characterization of Trehalase From Acyrthosiphon pisum, a Target for Pest Control

Insect trehalases are glycoside hydrolases essential for trehalose metabolism and stress resistance. We here report the extraction and purification of Acyrthosiphon pisum soluble trehalase (ApTreh-1), its biochemical and structural characterization, as well as the determination of its kinetic properties. The protein has been purified by ammonium sulphate precipitation, first followed by an anion-exchange and then by an affinity chromatography. The SDS-PAGE shows a main band at 70 kDa containing two isoforms of ApTreh-1 (X1 and X2), identified by mass spectrometry and slightly contrasting in the C-terminal region. A phylogenetic tree, a multiple sequence alignment, as well as a modelled 3D-structure were constructed and they all reveal the ApTreh-1 similarity to other insect trehalases, i.e. the two signature motifs ¹⁷⁹PGGRFRELYYWDTY¹⁹² and ⁴⁷⁹QWDFPNAWPP⁴⁸⁹, a glycine-rich region ⁵⁴⁹GGGGEY⁵⁵⁴, and the catalytic residues Asp336 and Glu538. The optimum enzyme activity occurs at 45 °C and pH 5.0, with K_m and V_max values of ~ 71 mM and ~ 126 µmol/min/mg, respectively. The present structural and functional characterization of soluble A. pisum trehalase enters the development of new strategies to control the aphids pest without significant risk for non-target organisms and human health.

High-level expression of highly active and thermostable trehalase from Myceliophthora thermophila in Aspergillus niger by using the CRISPR/Cas9 tool and its application in ethanol fermentation

Trehalase catalyzes the hydrolysis of the non-reducing disaccharide trehalose. The highly active trehalase MthT from Myceliophthora thermophila was screened from the trehalase genes of six species of filamentous fungi. An ingenious multi-copy knock-in expression strategy mediated by the CRISPR/Cas9 tool and medium optimization were used to improve MthT production in Aspergillus niger, up to 1698.83 U/mL. The protein background was dramatically abated due to insertion. The recombinant MthT showed optimal activity at pH 5.5 and 60 °C, and exhibited prominent thermal stability between 50 and 60 °C under acid conditions (pH 4.5-6.5). The ethanol conversion rate (ethanol yield/total glucose) was significantly improved by addition of MthT (51.88%) compared with MthT absence (34.38%), using 30% starch saccharification liquid. The results of this study provided an effective strategy, established a convenient platform for heterologous expression in A. niger and showed a potential strategy to decrease production costs in industrial ethanol production.