Journal of Lipid Research, Vol 20, 363-370, Copyright © 1979 by Lipid Research, Inc.
Positional distribution of fatty acids in the glycerophospholipids of Tetrahymena pyriformis
J Pieringer and RL Conner
The positional distributions of the fatty acids in the major
glycerophospholipids of Tetrahymena pyriformis W were analyzed. A
comparison was made of the acyl distributions in normal and ergosterol-
grown cells. It was assumed that the positional arrangement of fatty acids
would serve as an indicator of acyltransferase enzyme specificity. The
acyltransferases in this protozoan have substrate specificities that direct
unsaturated groups, particularly polyunsaturates, to the 2-carbon of the
glycerophospholipids. An exception is gamma-linolenic acid, which
represents a substantial proportion of the total acids at both carbons.
Saturated and iso-acids are esterified primarily at the 1-carbon. The
qualitative pattern of the fatty acyl distribution is the same in both
normal and ergosterol- grown organisms. Sterol substitution produces
quantitative differences in the acyl components at both the 1- and
2-carbons of the glycerophospholipids. These differences include a
shortening of the average chain length and a decrease in total unsaturation
at both the 1- and 2-positions. In addition, there is a modification at the
2-carbon in the relative amounts of the products of two pathways involved
in the biosynthesis of fatty acids. The data are interpreted to indicate
that the fatty acid transformations in the glycerophospholipids of
organisms that contain ergosterol are not the result of altered
acyltransferase specificities.
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