Gene identification and enzymatic properties of a membrane-bound trehalase from the ovary of Rhodnius prolixus.

Trehalose represents the main hemolymph sugar in most insects and its metabolic availability is regulated by trehalase. In this study, trehalase activity associated with the reproductive system was investigated in the insect Rhodnius prolixus, a hematophagous hemipteran vector of Chagas' disease. A single-copy gene that encodes a membrane-bound trehalase (RpTre-2) was identified in the genome of R. prolixus. RpTre-2 deduced amino acid sequence is closely related to other insect membrane-bound trehalases. The expression of this gene was detected in all analyzed organs, including ovary, where total trehalase enzymatic activity was determined, and was highest at day 7 after blood meal. Ovary membranes showed a major trehalase specific activity, which confirmed the presence of a membrane-bound trehalase in this insect. This trehalase activity seemed not to be regulated at transcriptional level, as the expression of RpTre-2 gene in the ovary did not change over the days after feeding. Similarly, ovarian follicles at different developmental stages did not show any variation in the transcription level of this gene. The RpTre-2 kinetic parameters were also investigated. Activity was highest at pH 5.5 and followed Michaelis-Menten kinetics, with an apparent K(m) = 1.42 ± 0.36 mM and Vmax = 167.90 ± 12.91 nmol/mg protein/h. These data reveal the presence of a membrane-bound trehalase in R. prolixus that is active in ovary and probably takes part in the insect carbohydrate metabolism associated with the reproductive process.