RESUMO
Activities of hexokinase (HK), glucose-6-phosphate dehydrogenase (G6PDH), fructose-6-phosphate kinase (F6PK), glutamate dehydrogenase (GlutDH), aspartate aminotransferase (AAT), malate dehydrogenase (MDH) and glycerol-3-phosphate dehydrogenase (GPDH) were determined in tissue extracts of testes and ovaries of adult Dipetalogaster maximus (Uhler) and Triatoma infestans (Klug) (Hemiptera: Reduviidae), insect vectors of Chagas disease. The fine structure organization of the same organs were studied by electron microscopy. Results allow the following inferences: in testes from both species, most of the glucose would be utilized through the glycolytic pathway. Amino acid catabolism for energy purposes appears to be unimportant. The number of mitochondria and the development of the rough endoplasmic reticulum in cells of the spermatogenic line indicate the occurrence of active oxidative metabolism and protein synthesis; in ovaries, levels of G6PDH indicate the existence of an active pentose pathway which would supply the NADPH required for fat and ecdysteroid synthesis. Amino acid catabolism appears to be relatively more important in ovary than in testis. Fat and glycogen are stored in follicular cells of D. maximus; oocytes of both species contain numerous fat droplets. Abundant mitocondria are present in follicular cells and oocytes. A well developed rough endoplasmic reticulum and free ribosomes are also conspicuous in these cells. The malate/aspartate H-transfer system seemed to be relatively more important than the glycerophosphate shuttle in ovaries as well in testes.
Assuntos
Insetos Vetores/enzimologia , Ovário/enzimologia , Oxirredutases/metabolismo , Testículo/enzimologia , Triatominae/enzimologia , Animais , Feminino , Insetos Vetores/ultraestrutura , Masculino , Microscopia Eletrônica , Ovário/ultraestrutura , Especificidade da Espécie , Testículo/ultraestrutura , Triatominae/ultraestruturaRESUMO
A fatty acid-binding protein (FABP) from the cytosolic fraction of the triatomine Dipetalogaster maximus (Uhler) flight muscles was purified by a procedure based on gel filtration, reverse-phase high performance liquid chromatography, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The protein has an apparent molecular mass of 14 kDa, and its N-terminus is unblocked. Its N-terminal sequence was obtained by submitting an SDS-PAGE band blotted onto a polyvinylidene difluoride membrane to Edman degradation. The sequence obtained indicates that this FABP belongs to the heart type. This is the first time that a fatty acid-binding protein has been reported for a triatomine. The presence of said FABP, abundant mitochondria, and lipid stores in the flight muscles of D. maximus suggests that beta oxidation of fatty acids is used by the triatomine thoracic muscle as an energy source, and could be related to its dispersal capacity.
Assuntos
Proteínas de Transporte/análise , Lipídeos/análise , Músculo Esquelético/química , Proteínas de Neoplasias , Triatominae/química , Animais , Proteínas de Ligação a Ácido Graxo , Voo Animal , Músculo Esquelético/anatomia & histologia , Análise de Sequência de Proteína , Triatominae/anatomia & histologia , Asas de AnimaisRESUMO
Effects of temperature and pH on the catalytic properties of hexokinase (HK, EC 2.7.1.1) from the flight muscles of Dipetalogaster maximus (Uhler) were studied. The enzyme showed a hyperbolic behavior with its two substrates (glucose and ATP). There was no inhibition by glucose. Apparent Km and Vmax increased as pH increased from 7.0 to 8.5. Catalytic efficiency was lowest at pH 7.0. Km, Vmax, and catalytic efficiency were higher at 37 degrees C than at 30 and 20 degrees C. There was marked inhibition by ATP, which was dependent on pH and temperature. Km values for ATP were reduced and catalytic efficiency increased as pH increased. Lowest Vmax was observed at pH 7.0. At this pH there was 87.3% inhibition by ATP, whereas it was only 5.7% at pH 8.5 (at 30 degrees C). Km, Vmax, and catalytic efficiency were higher at 37 degrees C than at 30 and 20 degrees C. The strong inhibition by ATP detected at 20 degrees C (pH 7.6) almost disappeared at 37 degrees C. Therefore, temperature could regulate hexokinase activity by modulating the inhibition produced by ATP. Glucose utilization and ATP production would be promoted when temperature rises from 30 to 37 degrees C. Because insect thoracic muscles increase their temperature over 30 degrees C during flight, this phenomenon elucidates a mechanism enhancing energy supply for muscle activity.