Electrically induced protein release from Schizosaccharomyces pombe cells in a hyperosmotic condition during and following a high electropulsation

A high-electric-field application of fission yeast cells under hyperosmotic conditions improved the electro-induced release of protein and cytoplasmic enzymes. A cell suspension was pulsed at 12.5 kV/cm for 10 ms in a batch system and immediately postincubated at 30°C. The total protein release rate from cells increased in the hypertonic solutions of 1.5–2.5 M sorbitol to approximately threefold higher than those in the hypotonic and isotonic solutions of 0–0.5 M sorbitol. The protein release rate in 2.0 M sorbitol greatly increased up to 4.5 h and then gradually increased after 7.5 h. The maximum activities of cytoplasmic enzymes, such as alcohol dehydrogenase and 3-phosphoglycerate kinase, were obtained at 7.5 h after electropulsation in 2.0 M sorbitol, yielding approximately 90% of the enzyme activity levels found in spheroplast lysate. On the other hand, the release rates of protease in vacuoles and invertase in periplasmic space did not depend on osmotic solutions during electric pulse application.