Long-term effects of the trehalase inhibitor trehazolin on trehalase activity in locust flight muscle

Abstract

SUMMARY Trehalase (EC 3.2.1.28) hydrolyzes the main haemolymph sugar of insects, trehalose, into the essential cellular substrate glucose. Trehalase in locust flight muscle is bound to membranes that appear in the microsomal fraction upon tissue fractionation, but the exact location in vivo has remained elusive. Trehalase has been proposed to be regulated by a novel type of activity control that is based on the reversible transformation of a latent (inactive) form into an overt (active) form. Most trehalase activity from saline-injected controls was membrane-bound (95%) and comprised an overt form (∼25%) and a latent form (75%). Latent trehalase could be assayed only after the integrity of membranes had been destroyed. Trehazolin, a potent tight-binding inhibitor of trehalase, is confined to the extracellular space and has been used as a tool to gather information on the relationship between latent and overt trehalase. Trehazolin was injected into the haemolymph of locusts, and the trehalase activity of the flight muscle was determined at different times over a 30-day period. Total trehalase activity in locust flight muscle was markedly inhibited during the first half of the interval, but reappeared during the second half. Inhibition of the overt form preceded inhibition of the latent form, and the time course suggested a reversible precursor–product relation (cycling) between the two forms. The results support the working hypothesis that trehalase functions as an ectoenzyme, the activity of which is regulated by reversible transformation of latent into overt trehalase.

Putative Sugar Transporters of the Mustard Leaf Beetle Phaedon cochleariae: Their Phylogeny and Role for Nutrient Supply in Larval Defensive Glands

“…Unlike glucose in mammals, the major blood (hemolymph) sugar of insects is often the disaccharide trehalose (α-D-glucopyranosyl-α-D-glucopyranoside) [4]–[6]. It is synthesized from glucose phosphates in fat body tissue and serves as a source of carbohydrates for various tissues including flight muscles [7], [8], intestinal tract [9], fat body [10] or ovaries [11]. Besides trehalose absorption, the absorption of other sugars, such as fructose, glucose, and galactose, has been shown for different insect tissues [12]–[17].…”

Trehalases: A neglected carbon metabolism regulator?

“…Interestingly, recently additional key regulatory roles of trehalases have been described, such as: in pathogen defense; in control of sucrose levels and homeostasis; in chitin synthesis, in cellular differentiation, and in stress tolerance, among others. [12][13][14][15][16][17][18][19] In addition, trehalase contrastingly different sub-cellular localizations have been reported, including the cytoplasm, the vacuole, the apoplast, or being bound to the plasma membrane and oriented to the apoplast. 16,[20][21][22][23] In fungi, trehalase activity and localization have been directly involved in regulating the trehalose content and its mobilization into the cytoplasm and during the symbiotic interaction of the ectomycorrhizal fungi several genes for trehalose metabolism are strongly upregulated.…”

“…23,24 In insects the regulation of trehalose degradation by trehalase is essential to supply the energetic requirements for the flight and the direct regulation for chitin biosynthesis during the insect development. 6,16,18,25,26 In higher plants, trehalose content is regulated by trehalase activity, which impacts directly on sucrose levels by negatively correlating sucrose synthase 1 expression levels and starch content. 14,15 Apparently, since trehalose accumulation is regulated by trehalase, this enzyme could be directly involved in regulating carbon partitioning, as well.…”

Regulation of trehalase expression inhibits apoptosis in diapause cysts ofArtemia

“…Trehalase, which is reported to play the major role in trehalose hydrolysis, was first observed in the fungus Aspergillus niger, but was subsequently found in many other organisms, including plants and animals [5][6][7]. Additional regulatory roles for trehalase have been described in pathogen defence, control of sucrose levels, chitin synthesis, cellular differentiation and stress tolerance [9][10][11]. Additional regulatory roles for trehalase have been described in pathogen defence, control of sucrose levels, chitin synthesis, cellular differentiation and stress tolerance [9][10][11].…”