Hormone biosynthesis of juvenile

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)... 

Up to the present, the last steps in the biosynthesis of juvenile hormone are those most satisfactorily established. It can be considered as proven that the ester methyl grouping is formed with the participation of methionine (Reibstein and Law, 1973), and this is followed by the formation of the 10,11-epoxy group (Pratt and Tobe, 1973 1974 Tobe and Pratt, 1974). Presumably the epoxy group plays a role in the binding to the respective carrier protein of the haemolymph. 

Biological activity P. are toxic to the corpora allata of insects and directly inhibit thereby the biosynthesis of juvenile hormones, and thus the larvae prematurely develop into pupa (Latin praecox=premature). In adults, egg ripening and thus the ability to reproduce is principally affected. The synthetic, so-called P. Ill (proallatocidin, 6-ethoxy-7-methoxy-2,2-dimethyl-2//-1-benzopyran), C,4H,g03, Mr 234.30, oil, bp. 109°C (13 Pa), has a 10-fold stronger activity than P. 11. ... 

Brevioxime 25 is a natural product isolated from Penicillum brevicompactum and displays in vitro inhibition of juvenile hormone biosynthesis. Two different synthetic approaches have been described for this molecule. Different authors carried out the cyclization of the unsaturated ketoamide 409 in the presence of nitrosyl chloride that directly produced cyclization and led to the oxime <2001SL257, 2001T8699>. Starting from the same... 

Figure 3. Outline of juvenile hormone biosynthesis based on Ref. 23.

Harring C. M. (1978) Aggregation pheromones of the European fir engraver beetles Pityokteines curvidens, P. spinidens, andE vorontzovi and the role of juvenile hormone in pheromone biosynthesis. Z. angew. Entomol. 85, 281-317. 

Taub-Montemayor T. E. Dahm K. H., Govindan B. and Rankin M. A. (1997a) Rates of juvenile hormone biosynthesis and degradation during reproductive development and diapause in the boll weevil, Anthonomus grandis. Physiol. Entomol. 22, 269-276. 

At the heart of any search for bioactive molecules is the need for effective bioassays. Several bioassays have been developed for the identification of compounds with anti-juvenile hormone (AJH) activity. The most common of these AJH bioassays involves the treatment of young larvae or nymphs with the potential AJH by incorporation into the diet or contact application, and then waiting for several days (or, in some cases, weeks) for precocious development (or other AJH response) to occur ( 1, ). Alternatively, AJH activity can be determined using jri vitro assays such as corpora allata cultures or epidermal cell cultures to monitor for inhibition of juvenile hormone (JH) biosynthesis (3-6) or blockage of the JH induced inhibition of pupal commitment (7), respectively. 

Pratt, O F., and Finney, J.R. (1977 . Chemical inhibitors of juvenile hormone biosynthesis in vitro. In Crop Protection Ajiftvrr.v (Mcbarlane, N.R., ed), pp. II3-132 Academic Press. London. 

An interesting review of the biosynthesis and transport of juvenile hormones in insects has appeared.17 The syntheses of the juvenile hormones JHI—JHIII (25)—... 

As early as 1934 Wigglesworth showed that the evolutionary differentiation of insects is regulated by a centre in the brain. In 1956 Williams obtained from Cecropia moth a highly active extract which produced anomalies in the metamorphosis of experimental insects. Following this first description of the action of juvenile hormone, Gilbert and Schneiderman (1958), then Williams et al. (1959) described the juvenile hormone action of lipid extracts obtained from different mammalian organs. The pure active substance was isolated first by Schmialek (1961) from feces of the yellow mealworm, Tenebrio Molitor, and identified as famesol (1), known as an intermediate product in steroid biosynthesis. Six years later, Roeller and co-workers (1967) elucidated the structure of the juvenile hormone isolated from the male of Cecropia. The hormone was ascribed the structure methyl ( , )-3,11-dimethyl-10,ll-epoxy-7-ethyl-2,6-tridecadienoate (2), and was called C,g-JH. Independent of these workers, Meyer et al. (1968) isolated also from Cecropia another juvenile hormone, ( , )-10,11-epoxy farnesenate (3), called C,g-JH. 

Similarly, the experiments of Matolcsy et al. (1974a 1974b 1975), in which several metabolite analogues of mevalonic acid and homomevalonic acid have been tested for anti-juvenile action, were unsuccessful. Support for the rationale that these metabolite analogues would block the formation of juvenile hormone at the mevalonate level was provided by the successful inhibition of cholesterol biosynthesis by mevalonate analogues in humans. Yet, a fluorinated mevalonate analogue, 4-fluoromethyl-4-hydroxy-tetrahydro-2H-pyran-2-one (FMev, 72) was found to act as a potent inhibitor of JH biosynthesis by Quistad and co-workers... 

Fig. (2). Rates of juvenile hormone III (JH III) biosynthesis by the corpora aiiata (CA) of the penuitimnte and final instars of the cockroach, Diploptera punctata [43]. The rate of biosynthesis, which is closely correlated to haemolymph titers, was measured by an in vitro JH III radiochemical assay [45, 46, 47], Each point represents the mean of 3-12 determinations. Arrows indicate approximate times of ecdysis (reprinted with kind permission from Academic Press).

Muthukrishnan J, Seifert K, Hoffmann KH, Lorenz MW (1999) Inhibition of juvenile hormone biosynthesis in Gryllus bimaculatus by Glycosmis pentaphylla leaf compounds. Phytochemistry 50 249-254... 

The biosynthesis of the insect juvenile hormone (19) continues to present incorporation problems. The acid 10-epoxy-7-ethyl-3,ll-dimethyltrideca-2,6-dienoic acid (20) acts as a substrate for the hormone in the giant silk moth, Hyalopkora cecropia. L-Methionine gave the ester methyl group. However, it did not contribute to the carbon skeleton whilst farnesol, farnesol pyrophosphate, propionate, and mevalonate were apparently not utilized for the biosynthesis of the hormone under the conditions of these experiments. There was a very low incorporation of [2- C]acetate into juvenile hormone. 

Abstract Pheromones are utilized by many insects in a complex chemical communication system. This review will look at the biosynthesis of sex and aggregation pheromones in the model insects, moths, flies, cockroaches, and beetles. The biosynthetic pathways involve altered pathways of normal metabolism of fatty acids and isoprenoids. Endocrine regulation of the biosynthetic pathways will also be reviewed for the model insects. A neuropeptide named pheromone biosynthesis activating neuropeptide regulates sex pheromone biosynthesis in moths. Juvenile hormone regulates pheromone production in the beetles and cockroaches, while 20-hydroxyecdysone regulates pheromone production in the flies. 

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