Catalyzes the ATP- and NADPH-dependent reduction of carboxylic acids to the corresponding aldehydes (By similarity). In vitro, also catalyzes the activation of medium/long-chain fatty acids as acyl-adenylates (acyl-AMP) (PubMed:19182784). a carboxylate + ATP + H(+) + NADPH = AMP + an aldehyde + diphosphate + NADP(+) a medium chain fatty acid + ATP + H(+) = a medium-chain fatty acyl-AMP + diphosphate a long-chain fatty acid + ATP + H(+) = a long-chain fatty acyl-AMP + diphosphate ATP + dodecanoate + H(+) = diphosphate + dodecanoyl-AMP ATP + H(+) + hexadecanoate = diphosphate + hexadecanoyl-AMP Binds 1 phosphopantetheine covalently. 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. Belongs to the ATP-dependent AMP-binding enzyme family. Carboxylic acid reductase subfamily.