12
F. B. SHORLAND
b. Phosplfwtidylethanolamine (Cephalin). Structure as in lecithin,
but choline is replaced by ethanolamine,
HO · CH 2 · CH 2 NH 2
c. Phosphatidyherine. Structure as in lecithin, but serine
HO · CH 2 · CH · COOH
I
NH 2
is substituted for choline.
In addition to the above, phospholipids without the nitrogenous
base and designated phosphatidic acids (64) were isolated earlier from
leaf tissues, such as those of cabbage. As, however, enzymes are present
in these tissues which rapidly remove the nitrogenous bases to give
phosphatidic acid, the occurrence in living tissues of any substantial
amounts of this substance is doubtful (65).
In the phospholipids, lyso forms with one fatty acid radical in the
a- or ^-position are possible. It is well known that snake venom hydrolyzes fatty acids in the «-position only. Studies on the ß-lyso forms
of phosphatidylcholine and phosphatidylethanolamine of egg yolk have
shown that, in accordance with the generally accepted view, the saturated acids are preferentially attached to the /^-position (66). On the
other hand, in milk glycerophospholipids unsaturated acids occur in both
the a- and ^-positions (67).
d. Plasmalogens. These are related to the phosphoglycerides, but the
α-hydroxyl group is occupied by an aldehyde (jointed as an acetal) in
place of a higher fatty acid (68) (V). Other evidence (68a) indicates
that the aldehydogenic chain is bound to the secondary hydroxyl group
of glycerol as an α,/3-unsaturated ether.
OH
CH 2 · O · CH · R
I
CH · O · CO · R'
I
CH 2 —O—PO—0—CH 2 · CH 2 · NH 2
I
OH
(V)
Plasmalogens also occur with choline attached to the phosphoric
acid radical as in lecithin described above (69, 70).
e. Polyphosphoglycerides. This class is represented by cardiolipin,
first isolated from heart muscle by Pangborn (71), who ascribed to it
the structure shown (VI).
F. B. SHORLAND
b. Phosplfwtidylethanolamine (Cephalin). Structure as in lecithin,
but choline is replaced by ethanolamine,
HO · CH 2 · CH 2 NH 2
c. Phosphatidyherine. Structure as in lecithin, but serine
HO · CH 2 · CH · COOH
I
NH 2
is substituted for choline.
In addition to the above, phospholipids without the nitrogenous
base and designated phosphatidic acids (64) were isolated earlier from
leaf tissues, such as those of cabbage. As, however, enzymes are present
in these tissues which rapidly remove the nitrogenous bases to give
phosphatidic acid, the occurrence in living tissues of any substantial
amounts of this substance is doubtful (65).
In the phospholipids, lyso forms with one fatty acid radical in the
a- or ^-position are possible. It is well known that snake venom hydrolyzes fatty acids in the «-position only. Studies on the ß-lyso forms
of phosphatidylcholine and phosphatidylethanolamine of egg yolk have
shown that, in accordance with the generally accepted view, the saturated acids are preferentially attached to the /^-position (66). On the
other hand, in milk glycerophospholipids unsaturated acids occur in both
the a- and ^-positions (67).
d. Plasmalogens. These are related to the phosphoglycerides, but the
α-hydroxyl group is occupied by an aldehyde (jointed as an acetal) in
place of a higher fatty acid (68) (V). Other evidence (68a) indicates
that the aldehydogenic chain is bound to the secondary hydroxyl group
of glycerol as an α,/3-unsaturated ether.
OH
CH 2 · O · CH · R
I
CH · O · CO · R'
I
CH 2 —O—PO—0—CH 2 · CH 2 · NH 2
I
OH
(V)
Plasmalogens also occur with choline attached to the phosphoric
acid radical as in lecithin described above (69, 70).
e. Polyphosphoglycerides. This class is represented by cardiolipin,
first isolated from heart muscle by Pangborn (71), who ascribed to it
the structure shown (VI).