Mediates the conversion of L-glyceraldehyde to glycerol in D-galacturonate catabolic process. Also able to reduce D-glyceraldehyde. glycerol + NADP(+) = H(+) + L-glyceraldehyde + NADPH glycerol + NADP(+) = D-glyceraldehyde + H(+) + NADPH Carbohydrate acid metabolism. Belongs to the aldo/keto reductase family.