Properties of Arginase from the Hepatopancreas of Giant Freshwater Prawn (Macrobrachium rosenbergii, de Man).

We describe the hepatopancreas arginase activity of freshwater prawn (Macrobrachium rosenbergii). The enzyme was isolated using reactive blue 2- agarose affinity chromatography and gel filtration on Sephadex G-150. The enzyme had a specific activity of 5.70 μmol/min/mg of protein. The enzyme exhibited a maximal activity at pH 8.5 and Km of 12.5 mM. The enzyme was capable of hydrolysing L-arginine and to a lesser extent, L-arginine monohydrochlorate and L-arginine monohydrate. The optimum temperature of the enzyme was 35 0C. The molecular weight as determined by gel filtration was approximately 160,000 dalton and SDS-PAGE, was 22,000 dalton. The different amino acids (L-lysine, L-cysteine, Lvaline, L-proline, L-aspartic acid, L-glutamic acid and L-serine) and metal ions (Ni2+, Co2+, Zn2+, Mn2+ and Mg2+) did not show any inhibition on the enzyme activity. The enzyme was activated with Mn2+ and different concentration of Mn2+ had no effect on the enzyme activity. EDTA, citrate and urea showed considerable inhibition on the enzyme activity.Key words: Freshwater prawn; arginase; uricotelism; invertebrates; hepatopancrea

In vitro induction of rat liver mitochondrial membrane permeability transition pore opening by solvent extracts of Momordica charantia leaves

Alteration of mitochondrial functions such as permeability transition (PT), a process associated with the uncoupling of oxidative phosphorylation, has been found to play a vital role in the apoptotic process induced by certain anti-cancer agents. When triggered, PT facilitates the release of mitochondrial apoptogenic proteins which in turn activate the caspase cascade of apoptosis. Thus, this study investigated the in vitro effects of varying concentrations (0.2, 0.4, 0.6, 0.8 and 1.0 mg/ml) of different leaf extracts [Crude Water-Soluble Extract (CWSE), Decoction (DE) and Methanol Extract (ME)] of Momordica charantia (M. charantia), a purported anti-cancer plant of the family Cucurbitaceae on normal rat liver mitochondria. Opening of mitochondrial membrane permeability transition pore (MMPTP) was spectrophotometrically assayed under succinate-energized condition. Results obtained showed concentration-dependent and significant (P<0.05) increases in the extents to which MMPTP opening was induced by the three extract types when compared with the control group. Inductions caused by CWSE and DE increased with increasing concentrations while those caused by ME decreased with increasing concentrations, giving the maximum induction at 1.0 mg/ml (8.1-fold increase) of CWSE and the least induction at 1.0 mg/ml (4.3-fold increase) of ME, respectively. Spermine, a reference inhibitor of MMPTP opening, reversed all observed openings. These results indicate that the tested leaf extracts of M. charantia are potent (CWSE being the most potent) MMPTP opening inducers and the pathway by which M. charantia causes apoptosis in cancer cells is probably mitochondrial-mediated (intrinsic).Keywords: Mitochondrial membrane permeability transition pore (MMPTP), Momordica charantia, Apoptosis, Spermine