The role of tyrosine in the tanning and sclerotization of the puparium of Drosophila melanogaster

Citation

Driskell, William Jack (1974) The role of tyrosine in the tanning and sclerotization of the puparium of Drosophila melanogaster. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Q7PS-1450. https://resolver.caltech.edu/CaltechETD:etd-10242005-153220

Abstract

The cuticle of insects is sclerotized and tanned by crosslinks between proteins formed by tyrosine derivatives. The pathway from tyrosine to the catechols incorporated into the crosslinks in the puparium of Drosophila, the structure of the crosslink, and other aspects of sclerotization and tanning of the Drosophila puparium were studied.

At puparium formation there is an influx of tyrosine into the puparium, where it is incorporated as a catechol. The turnover of this catechol is very rapid. Synthesis of N-acetyldopamine, the sclerotizing catechol of Calliphora, was observed. No storage form in the larva for the tyrosine incorporated at puparium formation exists other than the pool of free tyrosine and tyrosine-0-phosphate. No differences in the larval and prepuapl tyrosine metabolisms of wild type and ebony were observed.

Puparia were degraded by acid treatment and by enzymolysis and the degradation products were analyzed to determine the nature of the sclerotizing crosslink. A ketocatechol was extracted in considerable quantity from the puparium by acid. The catechol extractable as a ketocatechol is incorporated into the puparium at puparium formation. The amount of this catechol incorporated is equal to the amount of free tyrosine and tyrosine-0-phosphate lost from the hemolymph at puparium formation. The amount and type of ketocatechol as well as other tyrosine derivatives extracted by acid from puparium are the same for ebony and wild type.

Enzymolysis of the puparium yielded soluble products which contain the crosslink extractable as ketocatechol. These products were fractionated and found to be heterogeneous.

Possible structures and syntheses of the sclerotizing crosslink are discussed.

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