Open AccessSeparation and analysis of novel polyunsaturated mycolic acids from a psychrophilic, acid‐fast bacterium, Gordona aurantiaca
Author(s) -
TOMIYASU Ikuko,
YANO Ikuya
Publication year - 1984
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1984.tb07991.x
Subject(s) - mycolic acid , chemistry , double bond , degree of unsaturation , thin layer chromatography , alkyl , silica gel , trimethylsilyl , chromatography , stereochemistry , bacteria , organic chemistry , biology , mycobacterium , genetics
More than 30 molecular species of highly unsaturated mycolic acids, ranging from C 60 to C 78 and possessing between two and seven double bonds, have been obtained from a new genus of acid‐fast bacteria, Gordona aurantiaca. They were fully separated and identified as their trimethylsilyl ether derivatives by a combination of silica gel thin‐layer chromatography (TLC), argentation thin‐layer chromatography and gas chromatography/mass spectrometry (GC/MS). On silica gel thin‐layer chromatography two adjacent spots, corresponding to mycolic acids possessing different structures of straight‐chain and α‐alkyl branch, were detected. The lower spot was separated by argentation TLC into four subclasses: monoenoic (including a small amount of saturated), dienoic, trienoic and tetraenoic mycolic acids ranging from C 62 to C 74 , and possessing a C 16:0 , C 18:0 , or C 20:0 alkyl branch at the C‐2 position. The upper spot was separated by argentation TLC into five subclasses: dienoic (including a small amount of monoenoic), trienoic, tetraenoic, pentaenoic and hexaenoic (heptaenoic) acids ranging from C 64 to C 78 and possessing a C 18:1 or C 20:1 alkyl branch at the C‐2 position. These types of mycolic acid structure differ from those reported previously in Mycobacteria and Nocardia, in the numbers of both carbon atoms and double‐bonds and the intermediate length of the α‐alkyl branch. The characteristic polyenoic structure of the straight‐chain alkyl unit was also confirmed by GC/MS analysis of the meromycolaldehydes obtained after pyrolysis of the methyl mycolates. The major aldehydes obtained from the lower‐spot mycolic acids were C 44 , C 46 , C 48 , C 50 and C 52 , centering at C 50 , while those from the upper‐spot mycolic acids were C 48 , C 50 , C 52 , C 54 and C 56 , centering at C 54 . These aldehydes were also shown to possess between two and four double bonds in the lower‐spot and between two and seven double bonds in the higher‐spot mycolic acids, respectively. The physiological role of such highly polyunsaturated mycolic acids in psychrophilic acid‐fast bacteria is discussed.