Search PubMed⌕ Search

Biomedical subjects

B Schink

Publications and source records attributed to B Schink.

94 records · Page 6Linked to original sources
PubMed1980

The membrane-bound hydrogenase of Alcaligenes eutrophus: II. Localization and immunological comparison with other hydrogenase systems.

Immunological comparison of the soluble and the membrane-bound hydrogenase of Alcaligenes eutrophus revealed no common antigenic determinants shared by the native proteins, however, a small amount of cross-reacting material was detected after freezing and thawing. Immune precipitation assays supported previous observations indicating the membrane-bound hydrogenase to be localized in the outer surface of the cytoplasmic membrane. The membrane-bound hydrogenases of A. eutrophus and Pseudomonas pseudoflava showed close immunological relationship, and material cross-reacting to both antisera was found in membrane extracts of all hydrogen-oxidizing strains of Pseudomonas. Alcaligenes and Aquaspirillum. Material cross-reacting to the membrane-bound hydrogenase of Xanthobacter autotraphicus GZ 29 was found only in a few hydrogen-oxidizing bacteria. Material cross-reacting to the soluble hydrogenase of A. eutrophus was detected in strains of A. eutrophus and A. ruhlandii only. Comparison of the membrane-bound hydrogenase of A. eutrophus, P. pseudoflava and X. autotrophicus with hydrogenases of other physiological bacterial groups revealed serological relationship to the membrane-bound hydrogenases of the hydrogen bacteria and of Chromatium vinosum only. The results are discussed in terms of physiological, taxonomical, and evolutionary aspects.

Alcaligenes↗
PubMed1978

Mutants of Alcaligenes eutrophus defective in autotrophic metabolism.

Forty-four mutants of Alcaligenes eutrophus H 16 were isolated which grew poorly or not at all under autotrophic conditions. Four types were characterized with respect to their defects and their physiological properties. One mutant lacked both enzymes specific for autotrophic CO2 fixation, another one lacked both hydrogenases, and two mutants lacked either the membrane-bound or the soluble hydrogenase. Comparing the results of studies on these mutant types, the following conclusions were drawn: the lack of each hydrogenase enzyme could be partially compensated by the other one; the lack of membrane-bound hydrogenase did not affect autotrophic growth, whereas the lack of the soluble hydrogenase resulted in a decreased autotrophic growth rate. When pyruvate as well as hydrogen were supplied to the wild-type, the cell yield was higher than in the presence of pyruvate alone. Mutant experiments under these conditions indicated that either of both hydrogenases was able to add to the energy supply of the cell. Only the soluble hydrogenase was involved in the control of the rate of hydrogen oxidation by carbon dioxide; the mutant lacking this enzyme did not respond to the presence or absence of CO2. The suppression of growth on fructose by hydrogen could be mediated by either of both hydrogenases alone.

Alcaligenes↗
PubMed1978

Hydrogen metabolism in aerobic hydrogen-oxidizing bacteria.

A survey on organisms able to use molecular hydrogen as electron donor in the energy-yielding process is presented. In the group of the aerobic hydrogen-oxidizing bacteria so far two types of hydrogenases have been encountered, a NAD-reducing, soluble enzyme (H2 : NAD oxidoreductase) and a membrane-bound enzyme unable to reduce pyridine nucleotides. With respect to the distribution of both types of hydrogenases three groups of hydrogen-oxidizing bacteria can be diffentiated containing (i) both types (Alcaligenes eutrophus), (ii) a soluble enzyme only (Nocardia opaca lb), and (iii) a membrane-bound hydrogenase only (majority of genera and species). The results of studies on the NAD-specific hydrogenase of A. eutrophus are summarized. Results on the solubilization and purification of the membrane-bound hydrogenase of A. eutrophus are presented in detail. The enzyme was solubilized from purified membranes by Triton X-100 and sodium desoxycholate or phospholipase D. The crude membrane extract was fractionated by ammonium sulfate precipitation and chromatography on carboxymethylcellulose at pH 5.5. The enzyme was stable in potassium phosphate buffer; it resembles the soluble enzyme with respect to stability under oxidizing conditions. Further biochemical and immunological data indicate, however, that both enzymes are different with respect to their native structure.

Alcaligenes↗