Microbiology and physiology of anaerobic fermentation of cellulose. Progress report (4/30/91--4/30/92) and outline of work for the period 9/1/92--9/1/93 Page: 4 of 14
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against individual polypeptides of the cellulosome complex will
also be investigated. In preparation of the antibodies we will
first remove any carbohydrates from the polypeptides.
Thermoanaerobacter ethanolicus. We have published our results
on the isolation and characterization of the FDP-dependent lactate
dehydrogenase (Bryant, J. Enzyme Inhibition. 5, 235-248, 1991) and
alcohol dehydrogenases from mutant strains (Bryant et al. In
press). Present work is concentrated on the secondary alcohol
dehydrogenase. It is a remarkable enzyme with very broad
specificity. It reduces a number of both aliphatic and aromatic
compounds containing carboxy group to corresponding secondary
alcohols. The reaction is stereo-specific. This specificity
depending on the temperature (Pham et al. J. Am. Chem. Soc. 111,
1935, 1989). The enzyme is very thermostable. The work on this
enzyme which is being done in cooperation with Dr. Robert S.
Phillips of the Department of Chemistry at UGA has led to the
suggestions that its structure should be determined by X-ray
crystallography. To compliment the structure work we are now
cloning and sequencing the enzyme.
A second aspect of T. ethanolicus is an investigation of its
cellobiase or -glucosidase. The original goal was to obtain a
thermostable cellobiase to be inserted into C. thermoaceticum to
give it the ability to grow on cellobiose. It turned out that T.
ethanolicus has two cellobiases, one is constitutive, the other is
induced when the bacterium is grown on cellobiose. The first one
is hydrolyzing xylobiose and its main functions may be that of a
xylobiase. Both enzymes are being isolated and characterized. The
induced cellobiase has a very high thermostability and we will
attempt to clone it and insert it into C. thermoaceticum as
originally was planned. However, presently we do not have a system
for cloning into C. thermoaceticum. We propose to develop such a
system. Dr. S. Kushner, Head of the Department of Genetics, UGA
has kindly agreed to cooperate with us in this endeavor.
Clostridium thermoaceticum. We have finished the sequencing
of carbon monoxide dehydrogenase/acetyl-CoA synthase (CODH).
(Morton et al. J. Biol. Chem. 266, 23824, 1991). The enzyme is a
nickel-iron-sulfur protein consisting of two subunits in the form
of (0q)3. The a subunits consists of 729 amino acids (M, 81,730).
The fl subunit consists of 674 amino acids (Mr 72,928). No
significant homolog was found to any known sequence by computer
search of GenBank . The sequence of CO dehydrogenase from
Methanothrix soengenii has been published (Eggen et al. J. Biol.
Chem. 266, 6883, 1991). This enzyme consists of two large (79,
4kDa) and two small (19kDa) subunits. No extensive homology exists
between the two enzymes. However, two shorter sequences of the C.
thermoaceticum 0 subunit have homology with two sequences of the
large subunit of the M. soengenii enzyme. They are residues 495-
500 (VVATGC) and 548-551 (GSCV) of the C. thermoaceticum enzyme and
residues 544-549 and 583-586, respectively, of the M. soehngenii
enzyme. Our long term goal of CODH is to identify the Ni and iron
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Ljungdahl, L.G. Microbiology and physiology of anaerobic fermentation of cellulose. Progress report (4/30/91--4/30/92) and outline of work for the period 9/1/92--9/1/93, report, December 31, 1992; United States. (digital.library.unt.edu/ark:/67531/metadc793657/m1/4/: accessed October 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.