Isolation and Characterization of a Carotenoid-carrying Lipoprotein in the Serum of Chum Salmon (Oncorhynchus keta) during Spawning Migration

抄録

Carotenoid-carrying lipoproteins (CCLs) were found in the high density lipoprotein (HDL, d=1.063-1.210g/ml) and the very high density lipoprotein (VHDL₂, d>1.210g/ml) fractions of the serum of chum salmon, Oncorhynchus keta. A CCL was isolated from the HDL fraction by a sequential ultracentrifugal technique, and DEAE-cellulose and gel nitration column chromatography. Gel filtration chromatography showed that the molecular weight of the CCL ranged from 30, 000 to 500, 000, with a peak at 70, 000 dalton. The CCL gave rise to two subunits whose molecular weights were 24, 000 and 12, 000 by SDS-PAGE. No disulfide bond was detected between the two subunits. The CCL was considered to be a cluster of molecular species of various particle sizes any of which was composed of the two subunits. The CCL had a pi at 5.1, and was rich in glutamic acid, alanine, leucine, and lysine. The CCL showed a high content of lipid (54%), which consisted mainly of cholesterol ester, cholesterol, triglyceride, phosphatidylcholine, and sphingomyelin. The CCL could maintain a consistent function irrespective of the physiological state of chum salmon.