Involved in the toluene-4-sulfonate degradation pathway. Does not discriminate between the sulfonate and the carboxyl substituents and can also be involved in the p-toluenecarboxylate degradation pathway. 4-formylbenzenesulfonate + H2O + NAD(+) = 4-sulfobenzoate + 2 H(+) + NADH Homodimer. Belongs to the short-chain dehydrogenases/reductases (SDR) family. TsaC2 is probably the product of a pseudogene and is not expressed, due to the absence of promoter-like sequences upstream of the operon tsaMBCD2.