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Metabolism of 1‐acyl‐2‐oleoyl‐ sn ‐glycero‐3‐phosphoethanolamine in castor oil biosynthesis
Author(s) -
Lin JiannTsyh,
Lew Karen M.,
Chen Jennifer M.,
Iwasaki Yugo,
McKeon Thomas A.
Publication year - 2000
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/s11745-000-547-5
Subject(s) - microsome , chemistry , incubation , biochemistry , biosynthesis , substrate (aquarium) , phosphatidylcholine , chromatography , stereochemistry , enzyme , phospholipid , biology , ecology , membrane
We have examined the role of 2‐oleoyl‐PE (phosphatidylethanolamine) in the biosynthesis of triacylglycerols (TAG) by castor microsomes. In castor microsomal incubation, the label from 14 C‐oleate of 1‐palmitoyl‐2‐[1‐ 14 C]oleoyl‐ sn ‐glycero‐3‐phosphoethanolamine is incorporated into TAG containing ricinoleate. The enzyme characteristics, such as optimal pH, and the effect of incubation components of the oleoyl‐12‐hydroxylase using 2‐oleoyl‐PE as incubation substrate are similar to those for 2‐oleoyl‐PC (phosphatidylcholine). However, compared to 2‐oleoyl‐PC, 2‐oleoyl‐PE is a less efficient incubation substrate of oleoyl‐12‐hydroxylase in castor microsomes. Unlike 2‐oleoyl‐PC, 2‐oleoyl‐PE is not hydroxylated to 2‐ricinoleoyl‐PE by oleoyl‐12‐hydroxylase and is not desaturated to 2‐linoleoyl‐PE by oleoyl‐12‐desaturase. We have demonstrated the conversion of 2‐oleoyl‐PE to 2‐oleoyl‐PC and vice versa. The incorporation of label from 2‐[ 14 C]oleoyl‐PE into TAG occurs after its conversion to 2‐oleoyl‐PC, which can then be hydroxylated or desaturated. We detected neither PE‐ N ‐monomethyl nor PE‐ N,N ‐dimethyl, the intermediates from PE to PC by N ‐methylation. The conversion of 2‐oleoyl‐PE to 2‐oleoyl‐PC likely occurs via hydrolysis to 1,2‐diacyl‐ sn ‐glycerol by phospholipase C and then by cholinephosphotransferase. This conversion does not appear to play a key role in driving ricinoleate into TAG.