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Fri Jun 14 04:39:08 EST 1996

> A major component of the insect cuticle is sclerotin;  is sclerotin a
> single protein or a mixture of proteins?  
> -- 
> _______________________________________________________________________________
> Lou Hom >K '93		       	    	"If brevity be the soul of wit, 

Hi Lou
I found following answer at

..newly emerged insects are usually white, the integument is 
very flexible and soft and the new instars are therefore
extremely vulnerable. Very quickly, another simple chemical 
reaction occurs that is shown in Fig. 11.5. Tyrosine
precursors are oxidized in a series of steps by hemocytes then 
delivered to the epidermis where it is transported to the
outer side of the cuticle through pore canals where the 
dihydroxyphenol intermediates are oxidized in a final step by
phenoloxidase enzymes to highly reactive quinones. These 
quinones then react twice with different proteins to form
bridging links turning the cuticle into an inert, hard and 
unextractable exocuticle. The tanned protein in the exocuticle is
called sclerotin, whereas any cuticle that remains untanned or is 
deposited after tanning is termed arthropodin. Thus
the exocuticle contains sclerotin and the endocuticle contains 

I hope that helps

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