Purification and properties of phospholipase A2 from the venom of scorpion, (Heterometrus fulvipes)

Phospholipase A2 was purified about 78 fold from the venom of scorpion Heterometrus fulvipes. The molecular weight of the enzyme was found to be 16,000 and it was optimally active at pH 7.4 and at 50 degrees C. The Km value of the enzyme was 1.8 x 10(-3) M. Calcium, Magnesium and Zinc ions stimulated whereas Mercury ion and EDTA inhibited the enzyme activity. This enzyme exhibited fluorescence emission maximum between 310-320 nm.     

Roles of an Unconventional Protein Kinase and Myosin II in Amoeba Osmotic Shock Responses

The contractile vacuole (CV) is a dynamic organelle that enables Dictyostelium amoeba and other protist to maintain osmotic homeostasis by expelling excess water. In the present study, we have uncovered a mechanism that coordinates the mechanics of the CV with myosin II, regulated by VwkA, an unconventional protein kinase that is conserved in an array of protozoa. Green fluorescent protein (GFP)-VwkA fusion proteins localize persistently to the CV during both filling and expulsion phases of water. In vwkA null cells, the established CV marker dajumin still localizes to the CV, but these structures are large, spherical and severely impaired for discharge. Furthermore, myosin II cortical localization and assembly are abnormal in vwkA null cells. Parallel analysis of wild-type cells treated with myosin II inhibitors or of myosin II null cells also results in enlarged CVs with impaired dynamics. We suggest that the myosin II cortical cytoskeleton, regulated by VwkA, serves a critical conserved role in the periodic contractions of the CV, as part of the osmotic protective mechanism of protozoa.     

Purification of isozymes of superoxide dismutase from groundnut (Arachis hypogea) seedlings

Groundnut seedlings contain five isozymes of superoxide dismutase. These isozymes were purified to homogeneity by ammonium sulfate precipitation, ionexchange chromatography on diethyl amino ethyl cellulose, gel filtration using Sephadex G100 and preparative gel electrophoresis. Manganese containing superoxide dismutase showed optimal activity at pH 7.8 whereas activity was one fifth at pH 9.8. This difference in the activity was not observed in case of copper-zinc enzymes.