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Characterization of inducible lysozyme activity in the hemolymph of Rhodnius prolixus
1Departamento de Biologia Geral, Universidade Federal Fluminense, Niterói, Brasil.
Abstract:
1. The characterization and partial purification of an induced lysozyme activity in the hemolymph of adult Rhodnius prolixus inoculated with Micrococcus lysodeikticus is described. 2. Little or no activity against M. lysodeikticus appeared in the first hours after inoculation, but the activity increased reaching a maximum 4 days later, which was maintained to day 12. 3. The activity was characterized as lysozyme on the basis of the following considerations: 1) pH optimum and thermostability at acidic pH; 2) rate of lysis negatively dependent on ionic strength; 3) binding to SP-Sephadex at pH 5.5; 4) apparent molecular weight of 15 kDal. 4. Crude or semi-purified enzyme preparations showed a high degree of stability during handling, freezing and thawing, and standing at 5 degrees C. 5. Incubation of abdominal fat bodies from treated insects resulted in the release of activity into the medium. 6. The relationship between induced lysozyme activity and its role as an insect defense mechanism is discussed.
Insights
This study describes induced lysozyme activity in Rhodnius prolixus hemolymph after bacterial inoculation. The enzyme showed stability and characteristics consistent with lysozyme, suggesting a role in insect defense mechanisms.
Area of Science:
- Insect immunology
- Biochemistry
- Entomology
Background:
- Rhodnius prolixus is a vector for Chagas disease.
- Insect immune responses involve various antimicrobial factors.
- Lysozymes are key enzymes in innate immunity.
Purpose of the Study:
- To characterize and partially purify an induced lysozyme activity in Rhodnius prolixus hemolymph.
- To investigate the temporal profile of this activity post-inoculation.
- To explore the potential role of this lysozyme in insect defense.
Main Methods:
- Hemolymph inoculation with Micrococcus lysodeikticus.
- Enzyme activity assays.
- Biochemical characterization (pH optimum, thermostability, ionic strength dependence, SP-Sephadex binding, molecular weight estimation).
- Incubation of insect fat bodies.
Main Results:
- Induced lysozyme activity was detected, peaking at 4 days post-inoculation and sustained until day 12.
- Characterization confirmed the activity as lysozyme based on acidic pH optimum, stability, ionic strength dependence, SP-Sephadex binding, and molecular weight (15 kDa).
- The enzyme preparation exhibited stability under various conditions, and fat bodies released activity into the medium.
Conclusions:
- Rhodnius prolixus possesses an inducible lysozyme activity in response to bacterial challenge.
- This lysozyme exhibits properties consistent with known antimicrobial enzymes.
- The findings suggest a role for lysozyme in the innate immune defense of Rhodnius prolixus.
