A cysteine protease that processes insect vitellin. Purification and partial characterization of the enzyme and the proenzyme.
A cysteine protease that initiates degradation of vitellin (Vt) in the orthopteran Blattella germanica, and its proprotease precursor, were purified from yolk and partially characterized. The protease, purified 300-fold, contains three peptides of Mr 27,000, 29,000, and 31,000. A comparison of the purified enzyme's action pattern on Vt in vivo and in vitro confirmed its role in Vt processing. Protease-deficient yolk (day 0 postovulation) contained peptides of Mr 35,500, 37,000, 39,000, and 41,000, which were absent from yolk with protease activity. These were replaced by three peptides of approximately Mr 29,000, at days 2-3, the same time in development that protease expression and acidification of yolk granules occur (Nordin, J. H., Beaudoin, E. L., and Liu, X. (1991) Arch. Insect Biochem. Physiol. 18, 177-192). Acidification of purified proprotease converted it to three peptides of approximately Mr 29, 000 with cysteine protease activity. This conversion also required participation of a cysteine protease. Activated proprotease had the same pH activity profile, susceptibility to inhibitors, and cathepsin classification (L) as the protease. These results indicate that the Vt-processing protease is derived from a proprotease, which is activated in vivo by a developmentally regulated decrease in intragranular pH.
Liu
X
X
Department of Biochemistry and Molecular Biology and Graduate Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Massachusetts 01003, USA.
McCarron
R C
RC
Nordin
J H
JH
D000818:Animals; D000962:Antimalarials / Q000494:pharmacology; D002850:Chromatography, Gel; D003546:Cysteine Endopeptidases / Q000302:isolation & purification* / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004527:Egg Proteins / Q000378:metabolism*; D004530:Egg Yolk / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000302:isolation & purification* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007930:Leucine / Q000031:analogs & derivatives / Q000378:metabolism; D008970:Molecular Weight; D009987:Orthoptera
D000962:Antimalarials; D015853:Cysteine Proteinase Inhibitors; D004527:Egg Proteins; D004792:Enzyme Precursors; D003546:Cysteine Endopeptidases; D007930:Leucine; C024974:E 64