Shrimp ovarian peritrophin (SOP), a major protein in jelly layer and cortical rods, plays a role in egg
protection after spawning. Previous study, sequence of SOP gene from Fenneropenaeus merguiensis (Fm-SOP)
was composed of domain A and domain B. The SOP domain A contains amino acid sequences between 1-80 of
Fm-SOP. The domain A had six conserved cysteines which have been found in many antimicrobial peptides. The
molecular weight of purified rSOP-A protein was about 9 kDa. The SOP domain B contains amino acid sequences
81-329 of Fm-SOP while SOP-B1 was amino acid sequence 182-275 of Fm-SOP. The molecular weight
of purified rHis-SOP-B and rHis-SOP-B1 protein were about 38.5 and 18.0 kDa, respectively. Antimicrobial activities
of rSOP-A, rHis-SOP-B and rHis-SOP-B1 protein were investigated by liquid growth inhibition assay. Minimal
Inhibition Concentration (MIC) of rSOP-A against Staphylococcus aureus, Escherichia coli, Vibrio harveyi, Candida albicans
and Fusarium oxysporum were 35, 280, 280, 570 and 15 µg/mL, respectively. The MIC of rHis-SOP-B against S.
aureus, V. harveyi and F. oxysporum were 30, 270 and 500 µg/mL, respectively. And the MIC of rHis-SOP-B1 against S.
aureus, V. harveyi and F. oxysporum were 20, 470 and 250 µg/mL, respectively. The rHis-SOP-B and rHis-SOP-B1 (1000
µg/mL) did not show antimicrobial activity against E. coli and C. albicans. Three purified proteins were able to agglutinate
V. harveyi in vitro, displayed a chitinase activity and proteinase inhibition. In addition the stability of the proteins was
tested and found decrease antimicrobial activity after incubation at 50 °C for 5 h.