NETHRAVATHY V., ANISA ATHHAR AND MRINALINI DEVI U.G.
Abstract
SOD activity is one of the major defense mechanism against oxidative stress for all the aerobic organisms and industrial production of this enzyme is very essential. The effect of 2 different levels of Dissolved oxygen (Uncontrolled DO and DO at 20%) on SOD production were evaluated. Increasing enzyme activity in S mellis cells cultivated under both conditions was detected in the early exponential phase and an active synthesis was observed during a period of intensive oxygen consumption. More over the time courses of SOD production show 2 maxima. 1st maxima is upto 48 hours. 2nd maxima is from 48 hours to 96 hours. The results demonstrated that the O2 level had a significant influence on SOD activity. Under high DO conditions higher levels of SOD were produced at 1stand 2nd maxima, reaching activities of about 112 and 124 U (mg protein)-1 respectively. The number of isoforms did not change under hyperoxic conditions when s mellis was exposed to an atmosphere of 20% O2. There was no significant change in Cu, Zn SOD activity, where as Mn SOD expression increased 10-12 fold by elevated DO. SO it appears that Mn-SOD is the primary defense in S. mellis cells against oxygen toxicity. The presence of 59 ng-atom copper and 52 ng-atom zinc (mg enzyme)-1 in the purified S.mellis Cu, Zn SOD was confirmed by atomic absorption spectrometry.