Scheme V.
Modest mimics of SOD enzymes (log kcat(O2•−)= 5.7–7). Some of those compounds have increased lipophilicity which allows higher intracellular accumulation and compensates largely for their inferior SOD-like activity. That has been most strikingly demonstrated with ortho MnTE-2-PyP5+ and its meta isomer, MnTE-3-PyP5+. With 10-fold lower kcat(O2•−), but with 10 fold higher cellular accumulation, MnTE-3-PyP5+ protected SOD-deficient E. coli to the same extent as did MnTE-2-PyP5+. For values of kcat(O2•−) please see [3,9,15].