1. FATTY ACID OCCURRENCE AND DISTRIBUTION
25
The main interest in the studies of fatty acid synthesis of C. kluyveri is the demonstration of a fatty acid cycle involving the participation
of acetyl coenzyme A as in the Lynen cycle, but differing from it in
that the regeneration of coenzyme A does not take place through the
citric acid cycle. Instead, the activation of acetate is initiated by the
phosphorylation of acetate (101, 137)
Acetate + ATP ;=± Acetyl phosphate + ADP
followed by the acetyl transfer through transacetylase to coenzyme A:
Acetyl phosphate + CoA ^ Acetyl CoA + Phosphate
Bernhard and associates (138) grew the mold Phycomyces blakesleeanus, which produces a wide range of fatty acids, on a glucose medium
to which was added C
14 -labeled acetate. At the beginning γ-linolenic
(octadeca-6,9,12-trienoic) acid was the most strongly labeled, but the
activity thereafter slowly decreased. The C 22 , C 24 , and C 26 acids showed
an increased activity as the experiment proceeded, reaching a maximum
at 4 days, and then the activity diminished slowly toward the end of
the experiment, which lasted 8 days. The activity of stearic acid was
low throughout, whereas that of palmitic acid tended to increase. The
activity of oleic and of linoleic acid remained high, the activity of latter
tending to increase toward the end of the experiment.
Further experiments (139) showed that the percentage of activity
of each of the fatty acids remained constant during growth and that
no hydrogenation of linoleic or linolenic acid to saturated acids therefore took place.
The results as a whole do not suggest the conversion of oleic into
the more highly unsaturated constituents; they therefore confirm generally the observations made on seeds.
IV. Relationships between Types and Distribution of Fatty Acids
and Their Biological Origin
A. INTRODUCTION
In this section it is necessary, because of the limited data, to base
conclusions mainly on the composition of the triglycerides in the depot
fats of different species. Occasionally, however, the lipid constituents
are mainly or wholly nonglyceridic as in Mycobacterium
tuberculosis
or in the seed lipids of the shrub Simmondsia californica, and so comparisons between the types and distribution of fatty acids cannot always be made on a uniform basis. In this section, for the most part the
25
The main interest in the studies of fatty acid synthesis of C. kluyveri is the demonstration of a fatty acid cycle involving the participation
of acetyl coenzyme A as in the Lynen cycle, but differing from it in
that the regeneration of coenzyme A does not take place through the
citric acid cycle. Instead, the activation of acetate is initiated by the
phosphorylation of acetate (101, 137)
Acetate + ATP ;=± Acetyl phosphate + ADP
followed by the acetyl transfer through transacetylase to coenzyme A:
Acetyl phosphate + CoA ^ Acetyl CoA + Phosphate
Bernhard and associates (138) grew the mold Phycomyces blakesleeanus, which produces a wide range of fatty acids, on a glucose medium
to which was added C
14 -labeled acetate. At the beginning γ-linolenic
(octadeca-6,9,12-trienoic) acid was the most strongly labeled, but the
activity thereafter slowly decreased. The C 22 , C 24 , and C 26 acids showed
an increased activity as the experiment proceeded, reaching a maximum
at 4 days, and then the activity diminished slowly toward the end of
the experiment, which lasted 8 days. The activity of stearic acid was
low throughout, whereas that of palmitic acid tended to increase. The
activity of oleic and of linoleic acid remained high, the activity of latter
tending to increase toward the end of the experiment.
Further experiments (139) showed that the percentage of activity
of each of the fatty acids remained constant during growth and that
no hydrogenation of linoleic or linolenic acid to saturated acids therefore took place.
The results as a whole do not suggest the conversion of oleic into
the more highly unsaturated constituents; they therefore confirm generally the observations made on seeds.
IV. Relationships between Types and Distribution of Fatty Acids
and Their Biological Origin
A. INTRODUCTION
In this section it is necessary, because of the limited data, to base
conclusions mainly on the composition of the triglycerides in the depot
fats of different species. Occasionally, however, the lipid constituents
are mainly or wholly nonglyceridic as in Mycobacterium
tuberculosis
or in the seed lipids of the shrub Simmondsia californica, and so comparisons between the types and distribution of fatty acids cannot always be made on a uniform basis. In this section, for the most part the