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R Bühler

Publications and source records attributed to R Bühler.

47 records · Page 3Linked to original sources
PubMed1982

Quantitation of alcohol dehydrogenase in human tissue and serum by an enzyme-linked immunosorbent assay (ELISA).

An enzyme-linked immunosorbent assay for human alcohol dehydrogenase (ADH) has been developed. The method is based on preventing anti-ADH antibodies from binding to ADH-coated polystyrene microtiter wells by preincubation with serial dilutions of ADH-containing samples. The test detects ADH below 50 ng/ml. The sensitivity of the assay is superior to the commonly used photometric method and is particularly useful to quantitate ADH in crude tissue homogenates and in serum. Enzymatically active as well as inactive ADH can be detected, shown by the longer half-life of the ADH antigenicity (6.5 months) as compared to the half-life of the enzymatic activity (3.5 months). Approximately 10% of the total soluble protein in liver homogenates was ADH protein. The specific activity was around 0.4 IU/mg. It was higher in "atypical" livers although the absolute amount of ADH protein in these livers was identical with that in normal livers. ADH protein paralleled ADH activity in liver, stomach, and kidney homogenates. Normal serum on the average contained 59 +/- 16 ng/ml ADH (n = 9). Activity at these levels lies beyond the limits of spectrophotometric detectability. Serum of patients with liver disease exhibited elevated ADH levels paralleled by increased gamma-glutamyl transpeptidase (GGT), glutamate oxalacetate transaminase (GOT), glutamate pyruvate transaminase (GPT), but not alkaline phosphatase (AP) activities.

Alcohol Dehydrogenase↗
PubMed1979

The size and number of intramembrane particles in cells of the photosynthetic bacterium Rhodopseudomonas capsulata studied by freeze-fracture electron microscopy.

By freeze-fracture electron microscopy, particles have been observed on the protoplasmic leaflet (PF face) of cytoplasmic and intracytoplasmic membranes of the photosynthetic bacterium Rhodopseudomonas capsulata. The particles are present under all culture conditions of chemotrophically and phototrophically grown cells. However, the number of particles per microM2 increased significantly when the formation of the photosynthetic apparatus in the membrane is induced. Intracytoplasmic membranes, where the bulk of photosynthetic activity is localized, always have a higher density of particles than cytoplasmic membranes. Under all conditions particles with a diameter of 9.5 nm dominate. The frequency of particles with diameters greater or smaller than 9.5 nm changed with culture conditions. A comparison of biochemical and electron microscopic data have lead us to the conclusion that the particles, formed under conditions which allow the synthesis of the photosynthetic apparatus, are composed of photochemical reaction centers and antenna light-harvesting bacteriochlorophyll I (B 875)-protein complexes. The total molecular weight of these particles is calculated to be 500,000.

Anaerobiosis↗
PubMed1978

Characterization of a restriction enzyme from Escherichia coli K carrying a mutation in the modification subunit.

The restriction enzyme from a restriction and modification-deficient strain of Escherichia coli K mutated in the modification gene (hsdM) has been purified using an in vitro complementation assay with a mutant restriction enzyme from a strain lacking only restriction. The restriction enzyme from the hsdM mutant lacks all of the activities that are associated with the wild type enzyme: binding of unmodified DNA to filters, cleavage, or methylation of unmodified DNA and ATP hydrolysis. It is shown that the enzyme from this hsdM mutant cannot bind S-adenosylmethionine, an allosteric effector in the restriction reaction. In the absence of enzyme activation by S-adenosylmethionine, no binding to unmodified DNA takes place. A comparison with other mutant restriction enzymes allows us to outline the biochemical role of the subunits of the E. coli K restriction endonuclease.

DNA Restriction Enzymes↗
PubMedDate not supplied

Human liver alcohol dehydrogenase: the unique properties of the "atypical" isoenzyme beta 2 beta 2-Bern can be explained by a single base mutation.

Two allelic variant alcohol dehydrogenase isoenzymes, beta 2 beta 2-Bern and beta 1 beta 1, coded by the ADH2 locus, were isolated from human livers of Caucasian origin. They represent the "atypical" and "typical" phenotype, respectively. beta 2 beta 2-Bern has a higher specific activity and a lower pH-optimum, has a higher kM for NAD+, is less susceptible to inactivation by iodoacetate, and cannot be activated with chloride ions. In order to define the structural basis for these properties, we determined the amino acid sequence difference between the beta 2-Bern and the beta 1 polypeptide chains. Peptides were prepared by cleavages with trypsin and CNBr, and were purified by exclusion chromatography and reverse phase high performance liquid chromatography. The structural analysis showed that beta 2-Bern differs at only one position from beta 1: Arg-47 in beta 1 is substituted for His-47 in beta 2-Bern. This exchange, which is identical to that reported for the beta 2-Oriental chain, alters the binding of the pyrophosphate group of the coenzyme NAD(H), and also that of iodoacetate, thus explaining the observed differences between beta 2 beta 2-Bern and beta 1 beta 1.

Alcohol Oxidoreductases↗