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Four suppression subtractive hybridization (SSH) cDNA libraries were constructed to identify differentially expressed salinity stress responsive genes of black tiger shrimp, Penaeus monodon exposed to high (55 ppt) salinity conditions. One each of the forward and reverse SSH cDNA libraries were developed from the gill and gut tissues of shrimp and clones having inserts larger than 300 bp were unidirectionally sequenced. Based on the sequence homology search, the identified genes were categorized for their putative functions related to a wide range of biological roles, such as nucleic acid regulation and replication, immune response, energy and metabolism, signal transduction, cellular process, structural and membrane proteins, stress and osmoregulation. Gene expression levels in response to high salinity conditions at 2 weeks post salinity stress for some of the differentially expressed genes (Na(+)/K(+)-ATPase α-subunit, glutathione peroxidase, intracellular fatty acid binding protein, elongation factor 2, 14-3-3 like protein, penaeidin, translationally controlled tumor protein, transglutaminase and serine proteinase inhibitor B3) identified from SSH cDNA libraries were analysed by real-time RT-PCR. The highest gene expression levels was observed for Na(+)/K(+)-ATPase α-subunit in gill tissues (15.23-folds) and antennal glands (12.01-folds) and intracellular fatty acid binding protein in gut tissues (14.05-folds) respectively. The differential and significant levels of gene expression indicate the functional role of these genes in shrimp salinity stress adaptive mechanisms.

L-glutaminase is a therapeutic enzyme used in the treatment of acute lymphoblastic leukemia (ALL). In this study, the extracellular L-glutaminase produced by Bacillus subtilis strain JK-79 was purified to homogeneity. The purified L-glutaminase has specific activity of 937 U mg −1 with K M and V Max value of 8 × 10 -2 mM and 200 µM/ml min, respectively. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) confirmed it to have a molecular mass of 64 kDa. Further biochemical characterization revealed that the purified enzyme attained maximal activity at pH 7 and temperature 37°C. The enzyme was stable at 37°C for 60 min at physiologic-ph. The enzyme showed high specificity towards Lglutamine. The effect of metal ions on enzyme activity showed that NaCl, KCl and CaCl 2 enhanced the activity while AgCl 3 and CuCl 2 strongly inhibited the activity of the enzyme. The in-vitro antioxidant activity of the enzyme was investigated and the IC 50 value for DPPH and ABTS assay were 400 and 600 µg/ml, respectively. The purified enzyme showed cytotoxic activity against various Leukemic cell lines tested with IC 50 value of 231, 480, and 500 µg/ml for K562, U932 and Jurkat cell lines, respectively. Interestingly, L-glutaminase also revealed cytotoxic effect on other cancer cell lines such as MCF-7, OV1063 and HCA 7 with IC 50 value of 500, 526 and 750 µg/ml, respectively. Hence this enzyme from marine bacteria would possibly be an attractive candidate for further pharmaceutical use as a broad spectrum anti-tumor drug.

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