Abstract
A diacylglycerol-carrying lipoprotein (DGLP) was isolated from the hemolymph of adult male and female American cockroaches, Periplaneta americana. The purification procedure involved dialysis against distilled water, precipitation at low ionic concentration at pH 6.6, and separation by column chromatography on DEAE-cellulose. The final preparation was homogeneous as judged by polyacrylamide gel electrophoresis and electron microscopy. The lipoprotein comprised over 50% of the total hemolymph protein. The DGLP molecule was almost globular in shape with a diameter of approximately 160 A. The molecular weight, determined by a sedimentation-equilibrium method, was approximately 600,000. Apoprotein of DGLP consisted of two subunits, heavy chain (mol wt 250,000) and light chain (mol wt 85,000). The total lipid content of DGLP amounted to about 50%. The lipids comprised diacylglycerol (15% of total lipid), hydrocarbons (28%), cholesterol (5%), and phospholipids (43%). n-Pentacosane, 3-methylpentacosane, and 6,9-heptacosadiene were identified as major hydrocarbons. Mannose(0.9%) and glucosamine (0.3%) were associated with apoprotein of DGLP. The capacity of the purified DGLP to accept diacylglycerol from both fat body and midgut was demonstrated in vitro; thus it was suggested that the same carrier molecule served to transport this lipid from storage site and absorption site. The possible multiple role of cockroach DGLP in transporting such lipids as diacylglycerol, cholesterol, and hydrocarbon from the site of storage, absorption, or synthesis is discussed.
Highlights
A diacylglycerol-carrying lipoprotein (DGLP) was isolated from the hemolymph of adult male and female American cockroaches, Periplaneta americana
We report the physical and chemical characterization of DGLP, and demonstrate the presence of a considerable amount of hydrocarbon in DGLP, in addition to diacylglycerol
The DGLP radioactivity is associated with primary protein which is designated as "diacylglycerolsame bufferand additionalproteinfractions were carrying lipoprotein" (DGLP) in this paper
Summary
A diacylglycerol-carrying lipoprotein (DGLP) was isolated from the hemolymph of adult male and female American cockroaches, Periplaneta americana. Our recent study [8] has revealed that in the American cockroach, Periplaneta americana, diacylglycerol is the predominant lipid transported from the fat body and from the gut, and has suggested that lipoprotein(s) is involved in transporting this lipid from the two organs It is not known if specific lipoproteins are required for different transporting functions or if a single molecule can serve more than one physiological role. The present report describes a procedure for the isolation and purification of a diacylglycerol-carrying lipoprotein (DGLP) from hemolymph of the adult American cockroach, and demonstrates the capacity of the purified DGLP to accept diacylglycerol from both the fat body and the midgut. We report the physical and chemical characterization of DGLP, and demonstrate the presence of a considerable amount of hydrocarbon in DGLP, in addition to diacylglycerol
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