Catalyzes the reduction of a wide range of aldehydes into their corresponding alcohols. Has a strong preference for NADPH over NADH as the electron donor. Cannot use a ketone as substrate. Is a major source of NADPH-dependent aldehyde reductase activity in E.coli. The in vivo functions of YahK has yet to be determined. a primary alcohol + NADP(+) = an aldehyde + H(+) + NADPH Binds 2 Zn(2+) ions per subunit. kcat is 11.2 sec(-1) for acetaldehyde reduction. kcat is 11.6 sec(-1) for propionaldehyde reduction. kcat is 12.3 sec(-1) for glyceraldehyde reduction. kcat is 41.6 sec(-1) for butyraldehyde reduction. kcat is 32.1 sec(-1) for isobutyraldehyde reduction. kcat is 32.6 sec(-1) for crotonaldehyde reduction. kcat is 13.4 sec(-1) for glutaraldehyde reduction. kcat is 0.18 sec(-1) for 5-hydroxyvalerate reduction. kcat is 18.3 sec(-1) for hexanaldehyde reduction. kcat is 7.75 sec(-1) for benzaldehyde reduction. kcat is 12.5 sec(-1) for furfural reduction. kcat is 4.7 sec(-1) for butanol oxidation. kcat is 6.7 sec(-1) for 1,4-butanediol oxidation. Shows a constant increase in activity until 60 degrees Celsius using butyraldehyde as substrate. Belongs to the zinc-containing alcohol dehydrogenase family.