Catalyzes the oxidation of malonate semialdehyde (MSA) and methylmalonate semialdehyde (MMSA) into acetyl-CoA and propanoyl-CoA, respectively. 3-oxopropanoate + CoA + NAD(+) = acetyl-CoA + CO2 + NADH 2-methyl-3-oxopropanoate + CoA + H2O + NAD(+) = H(+) + hydrogencarbonate + NADH + propanoyl-CoA kcat is 7.4 sec(-1) with malonate semialdehyde as substrate. kcat is 1.1 sec(-1) with methylmalonate semialdehyde as substrate. Polyol metabolism; myo-inositol degradation into acetyl-CoA; acetyl-CoA from myo-inositol: step 7/7. Homotetramer. No effect on vanillin degradation. Belongs to the aldehyde dehydrogenase family. IolA subfamily.