Phospholipase A2 in hemocytes of the tobacco hornworm, Manduca sexta

Phospholipase A2 in salivary glands isolated from tobacco hornworms, Manduca sexta

“…So far, PLA2s from midgut contents of tiger beetles, mosquito larvae, screwworms, and tobacco hornworms, plus a PLA2 associated with oral secretions of adult burying beetles have been characterized to a limited extent (Nor Aliza and Stanley, 1998;Nor Aliza et al, 1999;Rana et al, 1997Rana et al, , 1998Uscian et al, 1995). Aside from these secretory enzymes, putative intracellular PLA2s have been described for tobacco hornworm fat body (Uscian and Stanley-Samuelson, 1993) and hemocytes (Schleusener and Stanley-Samuelson, 1996). The hemocyte PLA2 appeared to operate in eicosanoid biosynthesis because it exhibited a marked preference for arachidonylcontaining substrates (Schleusener and Stanley-Samuelson, 1996), and increased enzyme activity was stimulated by bacterial challenge (Tunaz et al, 2003).…”

“…Aside from these secretory enzymes, putative intracellular PLA2s have been described for tobacco hornworm fat body (Uscian and Stanley-Samuelson, 1993) and hemocytes (Schleusener and Stanley-Samuelson, 1996). The hemocyte PLA2 appeared to operate in eicosanoid biosynthesis because it exhibited a marked preference for arachidonylcontaining substrates (Schleusener and Stanley-Samuelson, 1996), and increased enzyme activity was stimulated by bacterial challenge (Tunaz et al, 2003). The salivary gland PLA2 also is able to hydrolyze 20:4n-6 from the sn-2 position of substrate PLs, although substrate specificities of PLA2s from insect sources have not yet been considered in detail.…”

An entomopathogenic bacterium, Xenorhabdus nematophila, inhibits hemocytic phospholipase A2 (PLA2) in tobacco hornworms Manduca sexta

“…Determination of PLA2 activities followed our routine protocols (Nor Aliza et al, 1999;Schleusener and Stanley-Samuelsson, 1996;Tunaz et al, 2003) in which release of radiolabeled arachidonic acid from phosphatidylcholine (1-palmitol, 2-arachidonyl [arachidonyl-1-14 C]) substrate was monitored by TLC.…”

“…The first step in eicosanoid biosynthesis is hydrolysis of AA from cellular PL pools, catalyzed by action of cellular phospholipase A2 (cPLA2; Baksinde et al, 1999;Dennis, 1997;Stanley, 2000). cPLA2s which are able to hydrolyze AA from the sn-2 position of PLs are present in tobacco hornworm fat body (Uscian and Stanley-Samuelsson, 1993) and hemocytes (Schleusener and Stanley-Samuelsson, 1996). The hemocyte cPLA2 is characterized by a marked preference for AA-linked PL substrate (Schleusener and Stanley-Samuelsson, 1996).…”

“…cPLA2s which are able to hydrolyze AA from the sn-2 position of PLs are present in tobacco hornworm fat body (Uscian and Stanley-Samuelsson, 1993) and hemocytes (Schleusener and Stanley-Samuelsson, 1996). The hemocyte cPLA2 is characterized by a marked preference for AA-linked PL substrate (Schleusener and Stanley-Samuelsson, 1996). More recently, we reported that bacterial infection stimulates increased PLA2 activity in tobacco hornworm hemocyte preparations (Tunaz et al, 2003).…”