A digestive phospholipase A2 in the tiger beetle Cicindella Cicindela circumpicta

Uscian, J.M.; Miller, J.S.; Sarath, G.; Stanley-Samuelson, D.W.

Journal of Insect Physiology 41.2: 135-141


ISSN/ISBN: 0022-1910
Accession: 037317711

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We report on phospholipase A sub(2) (PLA sub(2)) in the midgut contents of tiger beetles Cicindella circumpicta. PLA sub(2) is responsible for hydrolyzing fatty acids from the sn-2 position of dietary phospholipids (PLs), an essential step in the digestion and absorption of essential fatty acids. As expected from the background of mammalian digestive PLA sub(2)s, the midgut PLA sub(2) was Ca super(2+)-dependent. The PLA sub(2) in tiger beetle midgut contents was influenced by altering the reaction conditions, including incubation time, protein concentrations, pH and temperature. Routine assay conditions included incubating 3.3 mu g of protein prepared from midgut contents in Tris buffer (pH 9.0) for 30 min at 28 degree C. Partial purification on size-exclusion chromatography indicated that the molecular weight of the midgut PLA sub(2) is approximately 22 kDa. The partially purified PLA sub(2) was inhibited by the site-specific inhibitor oleyoxyethyl phosphorylcholine. The presence of the PLA sub(2) in the midgut contents is related to feeding activity, because the midgut contents of unfed beetles did not express PLA sub(2). We suggest that PLA sub(2)s are a common, and quite important, feature of insect digestive physiology.