<p> This enzyme, found in cyanobacteria, reduces a long-chain (mainly C16 or C18) fatty acyl ACP ester to its corresponding fatty aldehyde, releasing the acyl carrier protein (ACP) [<cite idref="PUB00055010"/>]. NADPH or NADH is the reductant for this reaction. This enzyme may be distantly related to the short-chain dehydrogenase or reductase (SDR) family (<db_xref db="PFAM" dbkey="PF00106"/>). The purpose of this reaction is in the first step of alkane biosynthesis (GenProp0942). </p>