Insects enzyme induction

Snyder M. J., Walding J. K. and Feyereisen R. (1995) Glutathione S-transferases from larval Manduca sexta midgut sequence of two cDNAs and enzyme induction. Insect Biochem. Mol. Biol. 25, 455 465. 

Detoxification enzymes such as cytochrome P450 monooxygenases, glutathione S-transferases, and hydrolases play important roles in the metabolism of and resistance to insecticides in insects. These enzymes possess the capacity for rapid increases in activity in response to chemical stress, a phenomenon known as enzyme induction. Readers are referred to reviews by Terriere and Yu (1974), Terriere (1984), Brattsten (1979), Yu (1986a, 1996, 2001) and Feyereisen (2005) for discussion of work pertaining to induction of detoxification enzymes in insects. 

Yu, S.J., 1988. Enzyme Induction as Detoxication Mechanism in Phytophagous insect. Symposium on Insect Biochemistry and Physiology, pp. 49-68. 

Yu SJ (1983) Induction of detoxifying enzymes by allelochemicals and host plants in the fall armyworm. Pestic Biochem Physiol 19 330-336 Yu SJ (1984) Interactions of allelochemicals with detoxification enzymes of insecticide-susceptible and resistant fall armyworms. Pestic Biochem Physiol 22 60-68 Yu SJ (1986) Consequences of induced foreign compound-metabolizing enzymes in insects. In Brattsten LB, Ahmad S (eds) Molecular aspects of insect-plant associations. Plenum, New York, pp 153-174... 

The inducibility of Prl by proteinaceous compounds released enzymatically from insect cuticle was also studied inM anisopliae (Paterson et al., 1994b). In the case of Schistocerca gregaria cuticle treated with KOH in order to remove proteins, no induction of Prl production was observed, while cuticle treated with chloroform or ether to remove lipids was able to induce enzyme production. Digestion of cuticle with Prl or the trypsin-like protease Pr2 ofM anisopliae resulted in peptides mainly in the range of 150-2000 Da. The addition of these peptides at 3 pg Ala equivalents ml"1 led to the induction of Prl production to a level (75%) similar to that observed in the case of untreated insect cuticle. The ability of various amino acids and peptides abundant in insect cuticular protein (Ala, Gly, Ala-Ala, Ala-Ala-Ala, Ala-Pro and Pro-Ala) to induce Prl was tested but none of them was found to increase enzyme production in the levels observed with cuticle, or peptides enzymatically released from the cuticle. 

Yu, S. J., Consequences of induction of foreign compound-metabolizing enzymes in insects, in Molecular aspects of insect-plant associations, Brattsten, L.B. and Ahmad, S., Eds., New York Plenum Press, 1986, p. 153. 

As mentioned earlier, atrazine induces various detoxification enzymes in insects. Table 9.18 shows that the induction by atrazine was associated with decreased toxicity of carbaryl, permethrin, and indoxacarb but increased toxicity of methyl parathion, phorate, and trichlorfon in fall armyworm larvae. The increased toxicity of methyl parathion and phorate was likely due to enhanced microsomal desulfuration and sulfoxidation, respectively, by atrazine (see the following text for explanation). 

Terriere, L.C., Induction of detoxication enzymes in insects, Annu. Rev. Entomol., 29, 71,1984. 

Once consumed, allelochemics have assorted deleterious effects. Otherwise, they can pass through the insect with no effect, be sequestered, or detoxified. Many enzyme systems are involved in biochemical defense against plant allelochemics, but the most familiar and perhaps most important are the mixed function oxidases. Brattsten (1979) describes the three major characteristics that contribute to their importance in biochemical waste disposal (i) they catalyze numerous oxidative reactions that produce more polar and hence more excretable compounds, (ii) they are non-specific in that a wide range of chemicals are acceptable substrates, (iii) they can adjust rapidly (within minutes) to the presence of allelochemics or synthetic insecticides via induction. The MFO detoxification system is not confined to insects MFO activity has been identified in a wide range of vertebrates and invertebrates. A variety of flies, mosquitoes, cockroaches, crickets and a minimum of 40 species of Lepidoptera (as well as representatives from other insect orders) possess MFO activity (review Brattsten, 1979). 

Induction of MFO activity in insects to synthetic insecticides was discovered nearly two decades ago. This phenomenon as mediated by natural plant products has received increased attention in the last few years. Induction refers to the temporarily accelerated production of enzyme protein. A large number of natural plant chemicals are known to induce the MFO system (Brattsten et al., 1977) and host plant allelochemic induction of MFO activity may mediate resistance to synthetic insecticides as well (Yu etal., 1979). There can also be genetic bases to cross-resistance between pesticides and plant defenses (Gould et al., 1982), thus posing another significant consideration in breeding host plant resistance. 

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