| Autor: |
Peter, Martin G., Shirk, Paul D., Dahm, Karl H., Roller, Herbert |
| Zdroj: |
Zeitschrift für Naturforschung C; August 1981, Vol. 36 Issue: 7-8 p579-585, 7p |
| Abstrakt: |
The accessory sex glands (ASG) of adult male Cecropia contain an enzyme that methylates juvenile hormone acids (JH-acids) in the presence of S-adenosyl-L-methionine (SAM). The methyltransferase is highly specific. The reaction rates decrease in the order JH-I-acid, JH-II-acid and JH-III-acid; in each case the natural enantiomer is esterified predominantly. Methyltrans ferase activity with the same substrate specificity was also demonstrated in adult female corpora allata (CA). Male CA have only marginal methyltransferase activity. The CA of male H. cecropia contain substantial amounts of JH-I-acid and JH-II-acid (minimum: 5 pmol/pair). When kept in organ culture, they release JH-acids into the medium. Radiolabeled propionate and mevalonate are incorporated efficiently into the carbon skeletons of the JH-acids. The enzyme system performing these transformations cannot be forced to produce JH-III-acid even in the presence of high mevalonate concentrations, though homomevalonate may enhance biosynthesis of JH-I-acid and JH-II-acid more than tenfold. It becomes evident that the regulation of JH titer balances with regard to the homologous structures during insect development is not merely a question of the availability of low molecular weight precursors, but in addition that of highly specific enzymes acting as regulatory entities in the later steps of the biosynthetic sequence. |
| Databáze: |
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