Purification of sorbitol dehydrogenase from diapause eggs of Dysdercus cingulatus (Fabricus 1775)

Sorbitol Dehydrogenase (SDH) is important enzymes responsible for the protection of eggs from harsh condition as it convert fructose to sorbitol which serves as polyol and stabilize the soluble proteins and lipid bilayer. The enzyme SDH (d-Idiol NAD oxidoreductase EC 1.1.1.14) is purified from the eggs of red cotton bug, Dysdercus cingulatus exposed to low temperature. The SDH from eggs were purified by using different protein purification technique viz, ion exchange chromatography, gel filtration and SDS-PAGE. The ion exchange chromatography showed 0.185U total activity, with a purification fold of 1.48 and yield 3.36%. Gel filtration chromatography showed an increase in purification of SDH activity by 2.73 with 0.095 U total activity and yield of 1.73%. SDS-PAGE revealed that SDH molecular weight of 3 8 KDa. The Km value of Fructose: NADH is 0.4: 0.01 and the Vmax was 0.6 and 0.03. Thus low temperature increases the activity of SDH which convert fructose to sorbitol which protects the cell during diapause condition.