A low molecular weight zinc-copper lipolytic protein from chick liver

A lipolytic zinc-copper protein has been isolated from the cytosol of chick liver. This material had a molecular weight of 6000 daltons, contained four atoms of zinc and one atom of copper per molecule. The 6000 dalton fraction aggregated at high ionic strength or in the presence of sodium dodecyl sulphate. Lipolytic activity was observed towards triolein, tripalmitin, phosphatidyl choline and retinyl palmitate, and was stimulated by cholate, Ca and high NaCl concentrations, and was inhibited by sulphydryl reagents, inhibitors of serine esterases, alkaline phosphatase and chelating agents. It appears that this copper-zinc protein is distinct from metallothionein which has no lipolytic activity.