May reduce toxic product malonic semialdehyde to 3-hydroxypropionic acid, which is excreted. 3-hydroxypropanoate + NADP(+) = 3-oxopropanoate + H(+) + NADPH Up-regulated by the nitrogen regulatory protein C (NtrC also called GlnG) and repressed by RutR. Belongs to the nitroreductase family. HadB/RutE subfamily.