Delta(6) fatty acid desaturase introducing a cis double bond at carbon 6 of palmitoyl-[acyl-carrier protein](16:0-ACP), producing 16:1(6Z)-ACP (PubMed:7961667, PubMed:9144157). No activity with the coenzyme A ester of the fatty acid (PubMed:7961667). The position of the double bond is determined by its distance from the carboxyl end of the fatty acid (PubMed:7961667). Low activity with several saturated acyl-[acyl-carrier protein]s, including 14:0-ACP and 18:0-ACP (PubMed:7961667, PubMed:9144157). Requires reduced ferredoxin for detectable in vitro activity (PubMed:7961667). 2 H(+) + hexadecanoyl-[ACP] + O2 + 2 reduced [2Fe-2S]-[ferredoxin] = (6Z)-hexadecenoyl-[ACP] + 2 H2O + 2 oxidized [2Fe-2S]-[ferredoxin] Binds 2 Fe(2+) ions per subunit. Inhibited by KCN or H(2)O(2). Lipid metabolism; fatty acid metabolism. Belongs to the fatty acid desaturase type 2 family.