L-glutaminase is an important anticancer agent that is used extensively worldwide by
depriving cancer cells of L-glutamine. The marine bacterium, Halomonas meridian was isolated
from the Red Sea and selected as the more active L-glutaminase-producing bacteria. L-glutaminase
fermentation was optimized at 36 h, pH 8.0, 37 C, and 3.0% NaCl, using glucose at 1.5% and soybean
meal at 2%. The purified enzyme showed a specific activity of 36.08 U/mg, and the molecular weight
was found to be 57 kDa by the SDS-PAGE analysis. The enzyme was highly active at pH 8.0 and
37 C. The kinetics’ parameters of Km and Vmax were 12.2 10?6 M and 121.95 mol/mL/min,
respectively, which reflects a higher affinity for its substrate. The anticancer efficiency of the enzyme
showed significant toxic activity toward colorectal adenocarcinoma cells; LS 174 T (IC50 7.0 g/mL)
and HCT 116 (IC50 13.2 g/mL). A higher incidence of cell death was observed with early apoptosis
in HCT 116 than in LS 174 T, whereas late apoptosis was observed in LS 174 T more than in HCT 116.
Also, the L-glutaminase induction nuclear fragmentation in HCT 116 was more than that in the LS
174T cells. This is the first report on Halomonas meridiana as an L-glutaminase producer that is used
as an anti-colorectal cancer agent.