A lipoglycoprotein from hemolymph of healthy and diseased larvae of the Japanese beetle, Popillia japonica

Abstract

The major protein in the hemolymph of third-instar Popillia japonica larvae is a lipoglycoprotein (LGP). This protein was isolated from healthy larvae and larvae infected with Bacillus popilliae, a cause of milky disease. The LGP was separated by density gradient centrifugation and partially purified by exhaustive dialysis. During the course of milky disease, the concentration of LGP decreases markedly. Lipids associated with the LGP were extracted and characterized by thin-layer chromatography and gas-liquid chromatography. Fatty acids detected in significant amounts were palmitic (C 16), stearic (C 18), oleic (C 18:1), linoleic (C 18:2), and lignoceric (C 24). The relative concentration of palmitic acid was significantly reduced in LGP isolated from diseased larval hemolymph. Carbohydrate constituents released from LGP by hydrolysis were determined by gas-liquid chromatography of the trimethylsilylated derivatives. Mannose, glucose, and a trace of galactose were present in LGP from hemolymph of normal larvae; however, only trace quantities of any of these carbohydrates could be detected in the LGP from hemolymph of infected larvae. Amino acids present in the greatest amounts in the LGP were aspartic and glutamic acids. Appreciable quantities of tyrosine, leucine, and threonine were also present. The amino acid composition of LGP in hemolymph from healthy larvae did not differ significantly from that in diseased larvae.