Binding sites of -SH reagents in dividing sea urchin egg

Inhibition of cleavage of sea urchin eggs by -SH reagents was examined by varying their concentration, and the time and stage of the treatment during the first cleavage cycle. It was found that more than half of -SH groups in the ‘cortex protein’, localized in the cortical layer, reacted with p-chloromercuribenzoate (PCMB) when cleavage was suppressed, while other protein fractions of eggs revealed only a little binding of PCMB. The amount of non-protein -SH groups (NPSH) in the egg decreased to a level 50% that of the intact cell when cytokinesis was completely blocked by 1 mM PCMB. Even at lower PCMB conc., which did not block cell division, the NPSH level decreased to 60% and remained there. In pulse-treatment with 0.1 mM N-ethylmaleimide (NEM), which did not block cell division, NPSH groups reacted quickly with the reagent to protect protein -SH groups from the alkylation. However, if the concentration was increased, the pulse-treatment resulted in suppression of cleavage and alkylation of protein -SH groups, especially of cortex protein, accompanied by decrease in ATPase activity involved in the cortex protein fraction.     

Inhibition of red cell Ca-ATPase by vanadate

1. 1. The Mg²⁺- plus Ca²⁺-dependent ATPase (Ca²⁺-ATPase) in human red cell membranes is susceptible to inhibition by low concentrations of vanadate.

2. 2. Several natural activators of Ca²⁺-ATPase (Mg²⁺, K⁺, Na⁺ and calmodulin) modify inhibition by increasing the apparent affinity of the enzyme for vanadate.

3. 3. Among the ligands tested, K⁺, in combination with Mg²⁺, had the most pronounced effect on inhibition by vanadate.

4. 4. Under conditions optimal for inhibition of Ca²⁺-ATPase, the K for vanadate was 1.5 μM and inhibition was nearly complete at saturating vanadate concentrations.

5. 5. There are similarities between the kinetics of inhibition of red cell Ca²⁺-ATPase and (Na⁺ + K⁺)-ATPase prepared from a variety of sources; however, (Na⁺ + K⁺)-ATPase is approx. 3 times more sensitive to inhibition by vanadate.

Enhancement of production and activity of alkaline zinc metalloprotease from <Emphasis Type="Italic">Salinivibrio proteolyticus</Emphasis> using low intensity direct electric current and zinc nanoparticles

Objectives

To improve the production and activity of an alkaline zinc metalloprotease from Salinivibrio proteolyticus in response to ZnSO₄ (ionic and nanoparticle forms) and low intensity direct electric current (LIDC).

Results

A DC of 50 µA for 10 min increased enzyme production from 35 to 53 U ml^?1 when applied to the stationary phase bacterial cells. Zn²⁺ improved enzyme production better than zinc nanoparticles (52 vs. 43.5 U ml^?1). Zinc nanoparticles (0.5 mM) added to an enzyme reaction mixture containing casein (0.65 %) and 20 mM Tris/HCl buffer (pH 8) improved enzyme activity more than Zn²⁺ (42 vs. 36 U ml^?1).

Conclusion

LIDC exposure (50 µA, 10 min) to the stationary phase bacterial cells increases metalloprotease production in Salinivibrio. A low concentration of zinc nanoparticles (0.5 mM) increases maximum enzyme activity.