Role in insects

Biochemical Reactions. The quinones in biological systems play varied and important roles. In insects they are used for defense purposes, and the vitamin K family members, which are based on 2-methyl-... 

Conversion of a terminal alkyne to its alkynylsilane prevents loss of the relatively acidic terminal hydrogen (pKa of ethyne c. 25) during later synthetic steps. For example, the terminal hydrogen of propyne was masked whilst its propargylic anion was used in a synthesis of Cecropia juvenile hormone, a chemical which plays ail important role in insect development (Figure Si5.2). 

The steroids known to play major regulatory roles in insect development and metamorphosis all fall into the class of polyhydroxylated ketosteroids called ecdysones (19-22). With the exception of Makisterone A (a C2 ecdysteroid identified from the milkweed bug Oncopeltus fasciatus) the known insect ecdysteroids constitute a group of eight or nine steroids that differ from one another... 

To date, interest in the ecdysteroids has focused primarily on their role in insect molting and metamorphosis and it is perhaps somewhat unfortunate that bioassays for ecdysteroid activity have been restricted almost exclusively to evaluating their effect on the molting process. It now appears probable that molting is just one of several important regulatory functions (e.g., embryogenesis, reproduction) performed by the ecdysteroids and that we are only just beginning to scratch the surface of an insect steroid system that is equally as complex as that in vertebrate species. 

In view of their critical importance in regulating the growth and development of insects, the enzymes should continue to be viewed as potentially valuable targets around which to develop new pest control agents. This possibility is likely to become more realistic as the enzymes are further characterized and the full extent of their many roles in insect development are more fully understood. 

Propionate serves several unique and important roles in insects. It is used by some insects, in very small amounts, as a precursor to homomevalonate which is an intermediate in the biosynthesis of juvenile hormone (JH) II (1,2) and probably JH I and JH 0 as well. Much larger amounts of propionate and methylmalonate are needed for the biosynthesis of methyl branched hydrocarbons which are major cuticular components in most of the approximately 100 insect species whose cuticular lipids have been examined (3-7). Until recently, there was little information available on either the source of propionate or its metabolism in insects. In mammals vitamin B 2 Is a key cofactor in propionate and methylmalonate metabolism (B—9). Recent observations that some insect species lack or contain low levels of vitamin B 2 (10)... 

Trimedlure may exist in eight different isomeric forms, depending on which of the four dotted lines of Figure 3 the chlorine atom resides upon, and whether the methyl and ester groups are cis or trans. Our preparations of trimedlure are not pure compounds but mixtures of isomers. Trimedlure has been separated into two solid isomers and a liquid fraction. Tests at our Hawaii laboratory indicated that one of the solids and the liquid portion of trimedlure are attractive, but the other solid is not attractive 91). Apparently, stereoisomerism can play an important role in insect attraction. 

Methyl esters prepared from undecylenic acid and containing an episulfide group were tested as inhibitors of JH III epoxide hydrolase activity to evaluate its biological role in insects <2005MI140>. 

Hormones have an important role in insect metamorphosis. In many species, two classes of hormones, moltirp hormones (made by the prothoracic glands) and juvenile hormones (made by the corpora allata) act together to control metamorphosis. Each regulates the expression of different genes, so that a charpe in their relative concentrations causes metamorphosis, the development of different body patterns. 

Nathanson, J.A. "Cyclic AMP A Possible Role in Insect Nervous System Function", Ph.D. Thesis, Yale University, New Haven,... 

Severson, R.E, A.W. Johnson, and D.M. Jackson Cuticular constituents of tobacco Factors affecting then-production and their role in insect and disease resistance and smoke quality Recent Adv. Tob. Sci. 11 (1985) 105-174. 

Insects generally are able to synthesize alkaloids themselves or take them from feed. Alkaloids play an important role in insect metabolism, behavior, protection mechanisms, and species diversification. Many pyrrolizidine alkaloid-adapted insects convert host plant pyrrolizidine alkaloids into insect pyrrolizidine alkaloids. In this operation, the acid component of plant alkaloid is replaced by 2-hydroxy acids of insect origin. This seems to be an effect of physiological adaptation and evolutionary changes in the muton. Insect pyrrolizidine alkaloids can be precursors of insect pheromone hydroxydanaidal in many species. 

I suggest that phytoalexins play an important role in insect resistance by plants. This role of phytoalexins and phytoalexin elicitation now should be studied further and tested under field conditions. 

CeCi-Phenolics and their derivatives have a range of biological activities. One such compound, salicylic acid (65), has extensive functions in plants (Leon et al., 1993 Raskin, 1992a, 1992b Yalpani et al., 1993). Others are involved in plant movements, play developmental roles, are participants in plant-insect interactions and plant-plant interactions (allelopathy), or play defensive or pheromonal roles in insects. 

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