4.3.1.17 A65G site-directed mutagenesis of the human liver isozyme cSDH, large structural alterations, serine binding is not affected, overview 691069 4.3.1.17 A65S structure of A65S hSDH mutant is determined at 1.3 A resolution. Mutant shows decreased activity (50%) with substrate L-serine compared to wild-type. Mutant shows measurable activity with substrate D-serine 728723 4.3.1.17 A65S/V225S double mutant shows only 10% of activity with substrate L-serine compared to wild-type (100%). Double mutant shows very little but measurable activity with substrate D-serine 728723 4.3.1.17 C183A 135% of wild-type activity. Enzyme retains the positive cooperativity seen in the native enzyme 713970 4.3.1.17 C221A 70% of wild-type activity. Enzyme retains the positive cooperativity seen in the native enzyme 713970 4.3.1.17 C226A 100% of wild-type activity. Enzyme retains the positive cooperativity seen in the native enzyme 713970 4.3.1.17 C303A site-directed mutagenesis of the human liver isozyme cSDH, structural alterations, overview 691069 4.3.1.17 C304A 10% of wild-type activity. Mutant displays altered kinetics with a higher Km and a Hill coefficient indicating negative homotropic cooperativity 713970 4.3.1.17 C309A site-directed mutagenesis of the cancer cell isozyme cSDH, structural alterations, overview 691069 4.3.1.17 C343A inactive, mutants lacks the charge transfer absorbance at 400 nm that is indicative of the 4Fe-4S center 713970