Bacterial Expression and Simple Purification of Human Group X Secretory Phospholipase A2

Secreted group X phospholipase A2 (sPLA2-X) is one of the most effective mammalian PLA2 enzymes at hydrolyzing plasma lipoproteins and phospholipids in the membranes of intact cells, due in particular to its relatively high binding affinity to zwitterionic phospholipid substrates, such as phosphatidylcholine. The products of its enzymatic activity, lysophospholipids and free fatty acids, especially arachidonic acid, are involved in various physiological and pathological processes and currently being studied intensively. In spite of numerous studies, the biological roles of sPLA2-X have not been completely elucidated. With the aims of studying various cellular functions and designing effective enzyme inhibitors, we prepared a high amount of recombinant human sPLA2-X. Here we describe an effective Escherichia coli expression system, together with an in vitro refolding and simple purification procedure, that yields up to 10 mg of mature human sPLA2-X from a litre of culture. In contrast to the natural protein, the recombinant enzyme was produced in bacterial cells without the N-terminal propeptide, i.e. as a mature protein, and was not N-glycosylated. It however retained all the enzymatic properties for hydrolysis of vesicular substrates composed of either phosphatidylglycerol or phosphatidylcholine.