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Identification of yolk platelet-associated hydrolases in the oocytes of Rhodnius prolixus

✍ Scribed by Roberto H. Nussenzveig; Pedro L. Oliveira; Hatisaburo Masuda


Publisher
John Wiley and Sons
Year
1992
Tongue
English
Weight
588 KB
Volume
21
Category
Article
ISSN
0739-4462

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✦ Synopsis


The yolk platelets from Rhodnius prolixus, a blood-sucking bug, are composed mostly of vitellin and here are shown to contain at least two hydrolytic enzymes, a phosphatase and a cathepsin D-like proteinase. Both the proteinase and the phosphatase have an acid p H optimum. No hydrolytic activity was observed under alkaline or neutral conditions. Among several proteinase inhibitors tested, only pepstatin could abolish vitellin breakdown in vitro. The proteinase appears to be bound to the yolk platelet membranes. The phosphatase activity, using p-nitrophenyl phosphate a5 substrate, was enhanced after disruption of the platelet membrane by Triton X-l 00. This activity could be inhibited by tartrate but not by p-cloromercuribenzoate.


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## Abstract Inorganic polyphosphate (poly P) is a polymer of phosphate residues that has been shown to act as modulator of some vertebrate cathepsins. In the egg yolk granules of __Rhodnius prolixus__, a cathepsin D is the main protease involved in yolk mobilization and is dependent on an activatio