alpha-cyclodextrin extracts diacylglycerol from insect high density lipoproteins.
alpha-Cyclodextrins are water-soluble cyclic hexamers of glucose units with hydrophobic cavities capable of solubilizing lipophiles. Incubating alpha-cyclodextrin with high density lipophorin from Manduca sexta or Bombyx mori resulted in a cloudy, turbid solution. Centrifugation separated a pale yellowish precipitate. Thin-layer chromatography analysis of the lipid extract of the precipitate showed that the major lipid was diacylglycerol, while KBr density gradient analysis of the supernatant demonstrated the presence of a lipid-depleted very high density lipophorin. Transfer of diacylglycerol from lipophorin to cyclodextrin was specific to alpha-cyclodextrin and was not observed with beta- or gamma-cyclodextrins. pH had no effect on diacylglycerol transfer to alpha-cyclodextrin. However, the transfer was strongly dependent on the concentration of alpha-cyclodextrin and temperature. Increasing the concentration of alpha-cyclodextrin in the incubation mixture was associated with the formation of increasingly higher density lipophorins. Thus, at 20, 30, and 40 mm alpha-cyclodextrin, the density of B. mori lipophorin increased from 1.107 g/ml to 1.123, 1. 148, and 1.181 g/ml, respectively. At concentrations greater than 40 mm, alpha-cyclodextrin had no further effect on the density of lipophorin. alpha-Cyclodextrin removed at most 83;-87% of the diacylglycerol present in lipophorin. Temperature played an important role in altering the amount of diacylglycerols transferred to alpha-cyclodextrin. At 30 mm alpha-cyclodextrin, the amount of diacylglycerol transferred at different temperatures was 50% at 4 degrees C, 41% at 15 degrees C, 20% at 28 degrees C, and less than 3% at 37 degrees C. We propose that diacylglycerol transfers to alpha-cyclodextrin via an aqueous diffusion pathway and that the driving force for the transfer is the formation of an insoluble alpha-cyclodextrin-diacylglycerol complex.
Jouni
Z E
ZE
Department of Biochemistry and Center for Insect Science, Biological Sciences West, University of Arizona, Tucson, AZ 85721, USA.
Zamora
J
J
Snyder
M
M
Montfort
W R
WR
Weichsel
A
A
Wells
M A
MA
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D003505:Cyclodextrins / Q000737:chemistry*; D004075:Diglycerides / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D007313:Insecta; D008074:Lipoproteins / Q000378:metabolism; D008075:Lipoproteins, HDL / Q000737:chemistry*; D013696:Temperature; D047391:alpha-Cyclodextrins
D002352:Carrier Proteins; D003505:Cyclodextrins; D004075:Diglycerides; D008074:Lipoproteins; D008075:Lipoproteins, HDL; D047391:alpha-Cyclodextrins; C032830:lipophorin; C032613:alpha-cyclodextrin