2,5-didehydro-D-gluconate + AH2 => 2-dehydro-D-gluconate + A
2,5-didehydro-d-gluconate + ah2 => 2-dehydro-d-gluconate + a
2,5-didehydro-D-gluconate + AH2 => 2-dehydro-D-gluconate + A
2,5-didehydro-d-gluconate + ah2 => 2-dehydro-d-gluconate + a