Catalyzes the ATP- and NADPH-dependent reduction of carboxylic acids to the corresponding aldehydes. Catalyzes the reduction of a very wide range of aliphatic carboxylic acids as well as many aryl carboxylic acids. Aryl carboxylic acid substrates include substituted benzoic acids, phenyl-substituted aliphatic acids, heterocyclic carboxylic acids, and polyaromatic ring carboxylic acids. Cannot reduce benzaldehyde to benzyl alcohol. a carboxylate + ATP + H(+) + NADPH = AMP + an aldehyde + diphosphate + NADP(+) AMP + an aromatic aldehyde + diphosphate + NADP(+) = an aromatic carboxylate + ATP + H(+) + NADPH Binds 1 phosphopantetheine covalently. Is competitively inhibited by anthranilate when using benzoate as substrate. Vmax is 3 times higher than that of the natural enzyme when recombinant apo-Car is incubated with the purified PPTase Npt and CoA. Monomer. The N-terminal domain likely catalyzes substrate activation by formation of an initial acyl-AMP intermediate, the central region contains the phosphopantetheine attachment site, and the C-terminal domain catalyzes the reduction by NADPH of the intermediate thioester formed from the attack of the phosphopantetheine thiol at the carbonyl carbon of acyl-AMP (PubMed:17102130). Large-scale domain motions occur between the adenylation and thiolation states. Phosphopantetheine binding alters the orientation of a key Asp, resulting in a productive orientation of the bound nicotinamide. This ensures that further reduction of the aldehyde product does not occur (PubMed:28719588). 4'-phosphopantetheine is transferred from CoA to Ser-689 by Npt. The conversion of carboxylic acid into aldehyde involves three key steps: adenylation of the bound carboxylic acid substrate to form an AMP-acyl intermediate, formation of a thioester linkage between the acyl moiety and the phosphopantetheine prosthetic group, and reduction of the thioester intermediate to the aldehyde. Belongs to the ATP-dependent AMP-binding enzyme family. Carboxylic acid reductase subfamily.