Sulfate conjugation insects

Sulfate conjugates have been detected in vivo in numerous insect species following exposure to phenolic compounds. A sulfotransferase prepared from gut tissues of southern armyworm larvae has been shown to be active toward p-nitrophenol and steroids, including cholesterol, eedysone, and p-sitosterol (Yang and Wilkinson, 1972). 

As has been discussed in relation to sulfate conjugation, there is increasing evidence that phosphate formation may play a critical role in regulating insect steroids this is particularly true for steroids present in eggs and during early stages of embryonic development. 

Balance between the active and inactive forms of ecdysone and/or other ecdysteroids may be accomplished by the formation of conjugates such as sulfate esters or glucosides (20,27). The sulfation of phenols and a variety of sterols has been 3emonstrated in insect tissues and this, in close association with an appropriate sulfatase, would constitute a readily reversible mechanism whereby the required balance between active and inactive forms of ecdysteroids could be regulated (27). 

The ability of insect sulfotransferases to catalyze the sulfation of plant and insect steroids may simply reflect the broad substrate specificity of the enzymes. On the other hand, it may be indicative of a more important physiological function of the enzymes. Sulfate esters of cholesterol, campesterol and e-sitosterol have been identified in the meconium of tobacco hornworm (M. sexta) pupae ( ), and these steroids are known precursors of a-and e-ecdysone and other molting hormones in this species ( ). Further, there is evidence that houseflies (M. domestica) and diapausing pupae of M. sexta convert 22,25 bisdeoxyecdysone, a-ecdysone and 20-hydroxyecdysone into sulfate and glucoside conjugates ( ). 

Various mechanisms have been studied in relation to the inactivation of monoamines in insects, which include V-acetylation, oxidative deamination, ° 0-sulfate or (S-alanyl conjugation, and sodium-sensitive and sodium-insensitive uptake mechanisms. GC and MS properties were determined for a variety of biogenic amines as their DTFMB-TMS and DTFMB-TBDMS derivatives. Since the first application of HPLC-ED, it has become an increasingly important analytical tool on neuroscience. Recently, microbore HPLC-ED has become the method of choice for the determination of trace biogenic amines and their metabolites. 

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