Calcium-independent phospholipase A2: structure and function

The classical Ca2+-independent phospholipase A2 enzyme, now known as Group VIA PLA2, was initially purified and characterized from the P388D1 macrophage-like cell line. The corresponding cDNA was subsequently cloned from a variety of sources, and it is now known that multiple splice variants of the enzyme are expressed, some of which may act as negative regulators of the active enzyme. Group VIA PLA2 has a consensus lipase motif (GTSTG) containing the catalytic serine, is 85–88 kDa, and exists in an aggregated form. The enzyme contains multiple ankyrin repeats, which may play a role in oligomerization. The Group VIA enzyme exhibits lysophospholipase activity as well as phospholipase A2 activity, and it is capable of hydrolyzing a wide variety of phospholipid substrates. A major function of Group VIA PLA2 is to mediate phospholipid remodeling, but the enzyme may play other roles as well. Other Ca2+-independent PLA2 enzymes have more recently been identified, and it may be possible to discriminate between the various Ca2+-independent PLA2 enzymes based on sequence or inhibitor-sensitivity. However, the physiological functions of the newly identified enzymes have yet to be elucidated.