Ecdysteroid phosphates

The formation of phosphate esters of ecdysteroids constitutes a potentially valuable mechanism for storing high titers of insect steroids in a form that is inactive but that provides a readily available source of the active ecdysteroid. Embryos of . gregaria contain a phosphatase that can hydrolyze ecdysone 22-phosphate (36) and this enzyme could effect the controlled release of ecdysone and possibly other ecdysteroids at appropriate stages of insect development. 

Meconium of Manduca contains 3-epi-20-hydroxyecdysone as the major ecdysteroid. In Manduca ovaries and eggs, 26-hydroxyecdysone 26-phosphate is the major ecdysteroid occurring at levels of 31 pg/g in ovaries,... 

Though the ratio of 26-hydroxyecdysone to other ecdysteroids in eggs and ovaries of the THW can be as high as 20 1 (20), it was not anticipated that the C-26 hydroxyl would be the only position involved in conjugate formation. In a study In which the conjugate was labeled, RP-HPLC and radioassay analyses showed a radioactive peak preceding the peak of 26-hydroxyecdysone 26-phosphate. This... 

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