Quantitative and qualitative changes in proteins and shift in the utilization of amino acids for cuticle sclerotisation and energy release during development in Culex quinquefasciatus

Abstract

Whole body protein of Culex quinquefasciatus showed a gradual increase during development and the content in 1st instar larvae was 3% and in adults it was 5% on fresh weight basis. The amount of total free amino acids showed a gradual increase up to 4th instar larvae but a sharp decline in pupae and adults, because of the mobilization of amino acids for the formation of new proteins in pupae. Appearance of new protein bands was not prominent during larval development but pupation resulted in origin of new protein bands. Protein profile of adult male and female did not exhibit marked difference in SDS-PAGE. Activity of alanine aminotransferase showed a gradual elevation during larval development but an antiparallel pattern was shown by another related enzyme aspartate aminotransferase. The ratio of activity of AlAT: AsAT, which is an index of utilization of amino acids in Krebs cycle via keto acids, was always below 0.3 in larvae, elevated to 0.6 in adults, which may be a part of flight adaptation. Maintenance of high activity of glutamate dehydrogenase (GDH) by adult mosquitoes in comparison with their larvae is also a part of flight adaptation because GDH- Transaminase system is responsible for supplying pyruvic acid and oxaloacetic acid from amino acid pool to Krebs cycle. Activity of phenol oxidase (tyrosinase), which is an index of melanization of cuticle and defense against parasites, showed a sharp increase from first instar to adults. As the melanization and sclerotisation of C. quinquefasciatuswere practically completed by the 48 hour of eclosion, the activity of phenol oxidase showed a gradual retardation.