62
F. B. SHORLAND
The fatty acid compositions of the individual phospholipids isolated
from mammalian tissues are collected in Table XIX. The results shown
in Table XIX indicate very wide diflEerences in fatty acid composition of
individual phospholipids from the same tissues. It is perhaps to be
expected that the acetalphospholipid or plasmalogen fraction with the
fatty acids attached to the ß-hydroxyl group of glycerol should be
largely unsaturated (see Section II,B,3,d).
In the brain and egg lipids notable differences in fatty acid composition are shown between the phospholipids from the same tissues. In
brain, phosphatidylethanolamine as compared with phosphatidylserine
shows a much higher content of C 20 and C 22 unsaturated fatty acids. In
studies on egg yolk phospholipids, the phosphatidylethanolamine and
phosphatidylcholine were almost quantitatively separated. The phosphatidylethanolamine fractions as compared with the phosphatidylcholine
are shown to be much richer in stearic acid. The lesser amounts of Ci 8
unsaturated acids found in phosphatidylethanolamine as compared with
phosphatidylcholine consist largely of linoleic acid. In phosphatidylcholine, Ci 8 unsaturated acids are mainly oleic acid. The results in Table
XIX show a diversity in fatty acid composition between individual
phospholipids as well as between the same kind of phospholipid, e.g.,
phosphatidylethanolamine in brain as compared with that in egg yolk.
The former is much richer in unsaturated fatty acids but contains less
stearic acid.
Earlier investigations carried out on sphingomyelin show that the
fatty acid present in this lipid is not solely lignoceric as is sometimes
reported [cf. Hutt (297)]. For example, Rennkamp (298) records the
following fatty acid composition (weight %): stearic, 46; nervonic'(tetracos-15-enoic) and lignoceric, 34; palmitic, 2; arachidic, 2; behenic, 6, and
hexacosenoic, 10.
In the cerebrosides there are four different types of galactolipids [cf.
Deuel (299)], each of which contains a different fatty acid. Cerasine
contains lignoceric, phrenosine, cerebronic (α-hydroxytetracosanoic)
(300), nervone, nervonic (tetracos-15-enoic) (301), and oxynervone,
oxynervonic (a-hydroxytetracos-15-enoic) acid (302).
4. General Conclusions Concerning the Types and Distribution of Fatty
Acids in Phospholipids
The somewhat meager data concerning the fatty acid distribution
of phospholipids in the various forms of life restrict the possibility of
arriving at any firm generalizations. Nevertheless it is evident that the
differences found between the fats of land plants and of fish are preserved in the phospholipids. The polyunsaturated C 20 and C 22 acids,
F. B. SHORLAND
The fatty acid compositions of the individual phospholipids isolated
from mammalian tissues are collected in Table XIX. The results shown
in Table XIX indicate very wide diflEerences in fatty acid composition of
individual phospholipids from the same tissues. It is perhaps to be
expected that the acetalphospholipid or plasmalogen fraction with the
fatty acids attached to the ß-hydroxyl group of glycerol should be
largely unsaturated (see Section II,B,3,d).
In the brain and egg lipids notable differences in fatty acid composition are shown between the phospholipids from the same tissues. In
brain, phosphatidylethanolamine as compared with phosphatidylserine
shows a much higher content of C 20 and C 22 unsaturated fatty acids. In
studies on egg yolk phospholipids, the phosphatidylethanolamine and
phosphatidylcholine were almost quantitatively separated. The phosphatidylethanolamine fractions as compared with the phosphatidylcholine
are shown to be much richer in stearic acid. The lesser amounts of Ci 8
unsaturated acids found in phosphatidylethanolamine as compared with
phosphatidylcholine consist largely of linoleic acid. In phosphatidylcholine, Ci 8 unsaturated acids are mainly oleic acid. The results in Table
XIX show a diversity in fatty acid composition between individual
phospholipids as well as between the same kind of phospholipid, e.g.,
phosphatidylethanolamine in brain as compared with that in egg yolk.
The former is much richer in unsaturated fatty acids but contains less
stearic acid.
Earlier investigations carried out on sphingomyelin show that the
fatty acid present in this lipid is not solely lignoceric as is sometimes
reported [cf. Hutt (297)]. For example, Rennkamp (298) records the
following fatty acid composition (weight %): stearic, 46; nervonic'(tetracos-15-enoic) and lignoceric, 34; palmitic, 2; arachidic, 2; behenic, 6, and
hexacosenoic, 10.
In the cerebrosides there are four different types of galactolipids [cf.
Deuel (299)], each of which contains a different fatty acid. Cerasine
contains lignoceric, phrenosine, cerebronic (α-hydroxytetracosanoic)
(300), nervone, nervonic (tetracos-15-enoic) (301), and oxynervone,
oxynervonic (a-hydroxytetracos-15-enoic) acid (302).
4. General Conclusions Concerning the Types and Distribution of Fatty
Acids in Phospholipids
The somewhat meager data concerning the fatty acid distribution
of phospholipids in the various forms of life restrict the possibility of
arriving at any firm generalizations. Nevertheless it is evident that the
differences found between the fats of land plants and of fish are preserved in the phospholipids. The polyunsaturated C 20 and C 22 acids,