456
ERIC E. CONN
dation of DPNH only 40%. These results indicated that the added cytochrome made an alternate, antimycin-A-insensitive oxidation route available for DPNH oxidation in plant tissues. Lehninger (49) and associates drew similar conclusions in studies with submitochondrial fractions from rat liver and suggested that their results were due to the
presence of DPNH-cytochrome c reductase in their fractions. The latter
enzyme is insensitive to antimycin A (104).
Succinoxidase activity has been observed in particles (mitochondria)
isolated from bakers' yeast (105). These particles in turn have served
as a source for isolation of a soluble succinic dehydrogenase which
closely resembles its counterpart in beef heart mitochondria (106).
The oxidation of succinate and DPNH in bacteria is also associated
with a particulate fraction. However, there are some major differences
between these particles and the mitochondria which can be isolated
from cells of plants and animals. For example, the particles from Azotobacter vinelandii are much smaller than mitochondria (107, 108); the
diameter of the bacterial particles is only about 1% of that of animal
mitochondria. Secondly, the small bacterial particles from Azotobacter
vinelandii oxidize only succinate without additions. This is in contrast
to animal mitochondria, which can oxidize all of the intermediates of
the Krebs cycle without supplementation. The rate of succinate oxidation by the bacterial particles is auite rapid, however. Recently a particle isolated from Azotobacter vinehndii has been described as having
all of the properties of the electron transport particles prepared from
beef heart mitochondria (109). But in the bacteria there is nothing resembling the mitochondrion, and the activities described above are
localized in independent small particles. Other properties exhibited by
these particles have been observed and their significance has been discussed (107).
In their studies on oxidative phosphorylation in particulate preparations of Azotobacter vinelandii, Rose and Ochoa observed succinoxidase
activity (110). Succinoxidase has also been observed in particles from
Serratia marscescens (111), Mycobacterium phlei (112), Corynebacterium creatinovorans (113), Escherichia coli (114), Aerobacter aerogenes (115), and Bacillus stearothermophilus
(116).
DPNH oxidase activity has been observed in the particulate preparations from Azotobacter vinehndii (107, 110) and Mycobacterium phlei
(U2).
3. Evidence Based on Distribution of Components of the Chain
The major evidence for the cytochrome respiratory chain is based
on the widespread distribution of components of the chain. Of all the
ERIC E. CONN
dation of DPNH only 40%. These results indicated that the added cytochrome made an alternate, antimycin-A-insensitive oxidation route available for DPNH oxidation in plant tissues. Lehninger (49) and associates drew similar conclusions in studies with submitochondrial fractions from rat liver and suggested that their results were due to the
presence of DPNH-cytochrome c reductase in their fractions. The latter
enzyme is insensitive to antimycin A (104).
Succinoxidase activity has been observed in particles (mitochondria)
isolated from bakers' yeast (105). These particles in turn have served
as a source for isolation of a soluble succinic dehydrogenase which
closely resembles its counterpart in beef heart mitochondria (106).
The oxidation of succinate and DPNH in bacteria is also associated
with a particulate fraction. However, there are some major differences
between these particles and the mitochondria which can be isolated
from cells of plants and animals. For example, the particles from Azotobacter vinelandii are much smaller than mitochondria (107, 108); the
diameter of the bacterial particles is only about 1% of that of animal
mitochondria. Secondly, the small bacterial particles from Azotobacter
vinelandii oxidize only succinate without additions. This is in contrast
to animal mitochondria, which can oxidize all of the intermediates of
the Krebs cycle without supplementation. The rate of succinate oxidation by the bacterial particles is auite rapid, however. Recently a particle isolated from Azotobacter vinehndii has been described as having
all of the properties of the electron transport particles prepared from
beef heart mitochondria (109). But in the bacteria there is nothing resembling the mitochondrion, and the activities described above are
localized in independent small particles. Other properties exhibited by
these particles have been observed and their significance has been discussed (107).
In their studies on oxidative phosphorylation in particulate preparations of Azotobacter vinelandii, Rose and Ochoa observed succinoxidase
activity (110). Succinoxidase has also been observed in particles from
Serratia marscescens (111), Mycobacterium phlei (112), Corynebacterium creatinovorans (113), Escherichia coli (114), Aerobacter aerogenes (115), and Bacillus stearothermophilus
(116).
DPNH oxidase activity has been observed in the particulate preparations from Azotobacter vinehndii (107, 110) and Mycobacterium phlei
(U2).
3. Evidence Based on Distribution of Components of the Chain
The major evidence for the cytochrome respiratory chain is based
on the widespread distribution of components of the chain. Of all the