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Changes in lipid molecular species and sterols of microsomal membranes during aging of potato ( Solanum tuberosum L.) seed‐tubers
Author(s) -
Zabrouskov Vladimir,
Knowles N. Richard
Publication year - 2002
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/s11745-002-0896-0
Subject(s) - phospholipid , sterol , microsome , degree of unsaturation , microsoma , stigmasterol , chemistry , biochemistry , membrane lipids , glycolipid , biology , solanum tuberosum , cholesterol , botany , membrane , chromatography , enzyme
Abstract Changes in sterols and the molecular species composition of polar lipids from microsomal membranes were characterized as a prerequisite to determining how lipid chemistry affects membrane susceptibility to peroxidation during aging of potato tubers. Polar lipid content of the microsomal fraction fell 17% (protein basis) as tubers aged from 2 to 38 mon at 4°C. In younger seed‐tubers, PC concentration (protein basis) was the highest, followed by digalactosyldiacylglycerol (DGDG), PE, monogalactosyldiacylglycerol (MGDG), and PI. PC and PE increased 14 and 27%, respectively, whereas glycolipids fell 64 and PI 43% with advancing age. These changes resulted in PC and PE dominating the microsomal membrane lipids of 38‐mon‐old tubers. Nonpositional analysis of lipid molecular species across lipid pools showed an increase in 16∶0/18∶3, 18∶3/18∶3, and 18∶2/18∶3 (PC and PE only), and a decline in 18∶2/18∶2 and 16∶0/18∶2 (except for MGDG) with advancing tuber age. The increase in 18∶3‐bearing species effected a linear increase in double‐bond index (DBI) of PC and PE during aging. The DBI of DGDG did not change with age; however, it fell 65% for MGDG, resulting in an overall decrease in average microsomal DBI. In addition, Δ5‐avenasterol and stigmasterol concentrations increased 1.6‐ and 3.3‐fold, respectively, effecting a significant increase in the sterol/phospholipid ratio with advancing tuber age. The increase in sterol/phospholipid ratio and the possibility that the increased unsaturation of microsomal membranes reflects a compensatory response to maintain optimal membrane function in light of the age‐induced loss of galactolipid and PI are discussed.