Lipid-protein globules of avian egg yolk. Isolation and properties of globules stable in concentrated sodium chloride solution.
A new type of globular particle, the 'insoluble yolk globule', was isolated from the egg yolk of three avian species (hen, duck, and emu) by centrifugation or gel-filtration chromatography. These globules are stable in NaCl and urea solutions at concentrations that dissolve or disrupt other constituents of yolk, The isolated globules are about 1% of the dry yolk of hen's and duck's eggs but about 8% emu's-egg yolk. Most of these globules are less than 2 micrometer in diameter. Electron micrographs of sections show a preponderance of globules in the range 0.125-0.25 micrometer, each with a thick shell surrounding a feature-less anterior. Globules with the same appearance were seen in sections of unfractionated yolk. Two kinds of larger particles were also observed: (i) particles with a distinct outer membrane and a vesiculated interior; (ii) featureless spheres, possibly of lipid. The insoluble yolk globules comprise protein (8-11% by dry wt.), phospholipid (31-35% total lipid), triacylglycerols (49-53%), cholesterol (8%) and cholesteryl esters (2-3%); the variations being among species. The phospholipid is accessible to phospholipase C. The isolated protein is heterogeneous and resembles the apoprotein from the yolk low-density lipoprotein.
D000818:Animals; D001717:Birds; D002645:Chickens; D004372:Ducks; D004530:Egg Yolk / Q000032:analysis*; D005260:Female; D008055:Lipids / Q000032:analysis; D008074:Lipoproteins / Q000032:analysis* / Q000378:metabolism; D008854:Microscopy, Electron; D010740:Phospholipases / Q000378:metabolism; D011506:Proteins / Q000032:analysis
D008055:Lipids; D008074:Lipoproteins; D011506:Proteins; D010740:Phospholipases