Catalysis of the reaction: a 1-acyl-2-hexadecanoyl-glycerolipid + 2 H+ + O2 + 2 reduced - = a 1-acyl-2--glycerolipid + 2 H2O + 2 oxidized -. The this activity introduces an unusual trans double bond at carbon 3 of a palmitoyl group attached to the sn-2 position of glycerolipids.
1-18:1-2-16:0-phosphatidylglycerol trans-3 desaturase activity