Processing of crayfish hemocyanin subunits into phenoloxidase.
Hemocyanin and phenoloxidase are both copper-binding proteins involved in the immune system for a wide range of animal species. In crayfish, these proteins were purified and characterized from plasma and hemocytes, respectively. Recently, we have reported that the processing of one of the hemocyanin subunits occurs by a proteolytic cleavage under acidic conditions which results in the release of an antibacterial peptide designated as astacidin 1 from the C-terminus [J. Biol. Chem. 278 (2003) 7927]. In the present paper, we show that cleavage of crayfish hemocyanin subunit 2 at the N-terminal part results in that the processed hemocyanin exhibits phenoloxidase activity. The calculated mass of the cloned hemocyanin 2 is 78,372Da, which corresponds to the size obtained after SDS-PAGE under reducing conditions of the purified hemocyanin and pI is estimated to be 5.70. The complete hemocyanin 2 sequence shows 74% and 44% similarity with hemocyanin 1 and prophenoloxidase of crayfish, respectively. Crayfish hemocyanin exhibited phenoloxidase activity in presence of trypsin, but no activity could be detected if treated with sodium dodecyl sulfate. These results show that hemocyanin of crayfish is involved in several immune responses such as an oxygen carrier protein, as a precursor for an antibacterial peptide, and a molecule with phenoloxidase function.
College of Pharmacy, Pusan National University, Jangjeong Dong, Kumjeong Ku, Busan, Republic of Korea.
So Young
SY
Lee
Bok Luel
BL
Lee
Kenneth
K
Söderhäll
D000595:Amino Acid Sequence; D000818:Animals; D003400:Astacoidea / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D006433:Hemocyanins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D016415:Sequence Alignment; D014357:Trypsin / Q000378:metabolism
D006433:Hemocyanins; D014442:Monophenol Monooxygenase; D014357:Trypsin