Assists in the loading of diacylglycerol, generated from triacylglycerol stores in the fat body through the action of adipokinetic hormone, into lipophorin, the hemolymph lipoprotein. It increases the lipid carrying capacity of lipophorin by covering the expanding hydrophobic surface resulting from diacylglycerol uptake. It thus plays a critical role in the transport of lipids during flight in several species of insects. Has antibacterial activity against the Gram-positive bacteria L.monocytogenes (MIC=6.5 uM). Lacks antibacterial activity against the Gram-positive bacteria B.circulans, M.luteus, S.aureus, and S.lutea, and the Gram-negative bacteria E.coli D31, E.coli ATCC 25922, and S.typhimurium. Lacks antifungal activity against S.cerevisiae, P.pastoris, Z.marxianus, C.albicans, C.wickerhamii, A.niger, F.oxysporum, and T.harizianum. Equilibrium between a soluble monomer and a bound lipoprotein form. Apolipophorin-3 associates with lipophorin during lipid loading until each particle contains 9 or 14 molecules of apolipophorin-3. Secreted into hemolymph. Expressed in hemolymph (PubMed:17194500, PubMed:29289504). Also found in hemocytes and fat body (PubMed:29289504). By bacterial infection. Belongs to the insect apolipophorin-3 family. Lipid freight - Issue 59 of June 2005