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K Mosbach

Publications and source records attributed to K Mosbach.

At least 37 records · Page 2Linked to original sources
PubMed1979

N6-[N-(6-Aminohexyl)carbamoylmethyl]-coenzyme A. Synthesis and application in affinity chromatography and as an immobilized active coenzyme.

The synthesis of a new coenzyme A analogue, N6-[N-(6-aminohexyl)carbamoylmethyl]-CoA, suitable for immobilisation through its terminal amino group to support matrices, is described. The synthetic route starts with bis(CoA) and involves the following steps: alkylation with iodoacetic acid and rearrangement yielding bis(N6-carboxymethyl-CoA), elongation of the carboxymethyl terminal with 1,6-diaminohexane using carbodiimide to yield bis(N6-[N-(6-aminohexyl)-carbamoylmethyl]-CoA) and finally the splitting of this bis[CoA analogue) through reduction with dithiothreitol to give the final product in approximately 10% overall yield. This CoA analogue showed 'coenzymic activity' with the enzymes acetyl-CoA synthetase, phosphotransacetylase and succinic thiokinase. Covalent binding of the CoA analogue to Sepharose 4B was normally carried out using its S-(5-thio-2-nitrobenzoic acid) derivative as this allows a convenient way for determining the amount of ligand coupled, based on the amount of 5-thio-2-nitrobenzoic acid liberated from the gel after reduction with dithiothreitol. After covalent binding of the CoA analogue to water-soluble activated dextran 70, the analogue was recycled while present in an ultrafiltration cell using the enzymes phosphotransacetylase and citrate synthase. The reaction was followed by measuring the citrate formed on addition of acetylphosphate and oxaloacetate. In affinity chromatographic studies it was shown that the CoA-Sepharose preparation could bind the CoA-dependent enzymes citrate synthase and succinic thiokinase and these could be biospecifically eluted using soluble CoA.

Animals↗
PubMed1979

The use of biochemical solid-phase techniques in the study of alcohol dehydrogenase. 1. Some studies on subunit interactions in alcohol dehydrogenase with subunits covalently bound to agarose.

The EE and SS isozymes of horse liver alcohol dehydrogenase have been immobilized separately to weakly CNBr-activated Sepharose 4B. The resulting immobilized dimeric preparations lost practically all of their activity after treatment with 6 M urea. However, enzyme activity was regenerated by allowing the urea-treated Sepharose-bound alcohol dehydrogenase to interact specifically with either soluble subunits of dissociated horse liver alcohol dehydrogenase or soluble dimeric enzyme. The regeneration of steroid activity in the immobilized preparations after treatment of the bound S subunits with soluble E subunits seems to show that true reassociation of the enzyme had taken place on the solid phase, since only isozymes with an S-polypeptide chain are active when using 5 beta-dihydrotestosterone as substrate. The results presented in this paper indicate that immobilized single subunits of horse liver alcohol dehydrogenase are inactive and that dimer formation is a prerequisite for the enzymic activity.

Alcohol Oxidoreductases↗
PubMed1978

Covalent binding of an NAD analogue to liver alcohol dehydrogenase resulting in an enzyme-coenzyme complex not requiring exogenous coenzyme for activity.

1. The NAD analogue, N6-[N-(6-aminohexyl)carbamoylmethyl]-NAD, was covalently bound to horse liver alcohol dehydrogenase in a carbodiimide-mediated reaction and in such a way that it was active with the very same enzyme molecule to which it was coupled. 2. The degree of substitution, i.e. the number of NAD analogues per enzyme subunit, could be varied (0.3-1.6). In one preparation 1.6 coenzyme molecules were bound per subunit; the alcohol dehydrogenase activity of this preparation was 40% of the activity obtained after addition of free NAD in excess. 3. It was calculated that every fourth active site of this preparation was provided with a covalently bound functioning coenzyme analogue, and that this analogue had a cycling rate of about 40 000 cycles/h in a coupled substrate assay. 4. The presence of the covalently bound coenzyme made the active sites difficult to inhibit with a competitive inhibitor. For example, 10 mM AMP inhibited the activity of the preparation by 50% whereas a reference system containing native alcohol dehydrogenase was inhibited by 80% in spite of the fact that the reference system contained about 20 000 times as high a concentration of coenzyme.

Adenosine Monophosphate↗
PubMed1977

Enzyme thermistor determination of glucose in serum using immobilized glucose oxidase.

An enzyme thermistor assay for serum glucose is described. The glucose present in the sample is reacted in a small column containing glucose oxidase immobilized to controlled pore glass (single thermistor device). The heat produced in the primary reaction is measured directly in the column without any need for coupling reactions. The useful linear range is 0.01-0.45 mM glucose, permitting 50-fold dilution of serum samples. Advantages are low enzyme cost, due to the immobilization, insensitivity for the color or any turbidity of the sample, and no requirement for coenzyme or any ancillary reaction. Improved sensitivity and extended linear range (0.01--0.9 mM) can be attained through a secondary reaction using catalase. The application to glucose analysis of a split-flow enzyme thermistor equipped with a reference column to eliminate unspecific heat effects is also described. The enzyme thermistor determinations were also compared with a spectrophotometric continuous flow technique using a small column with immobilized glucose oxidase and 4-aminoantipyrine and phenol as color reagents.

Blood Glucose↗
PubMed1977

Aspects of microenvironmental compartmentation. An evaluation of the influence of restricted diffusion, exclusion effects, and enzyme proximity on the overall efficiency of the sequential two-enzyme system malate dehydrogenase--citrate synthase in its soluble and immobilized form.

Soluble bifunctional enzyme aggregates have been prepared by cross-linking the sequential enzymes malate dehydrogenase (EC 1.1.1.37) and citrate synthase (EC 4.1.3.7) using glutaraldehyde. The kinetic behaviour of this two-enzyme system in its aggregated and non-aggregated form was studied both in free solution and immobilized on Sepharose beads. This study was undertaken in order to distinguish between the following two factors which may account for the increased efficiency found in general in co-immobilized consecutive two-enzyme systems: (a) closer proximity between the participating enzymes and (b) establishment of a favourable microenvironment (such as higher local intermediate concentration caused by increased diffusional hindrance in the gel phase). It was found that in spite of a reduction of the distance between the two enzymes in the aggregated form by an estimated factor of 10(3), no kinetic advantage (shorter lag phase or higher steady-state rate) could be detected compared to the corresponding system with the two enzymes not linked to each other. However, both systems immobilized to Sepharose reached the steady-state rate of citrate formation almost immediately, in contrast to the corresponding free systems which exhibited pronounced lag phase. These results indicate that, at least in the above systems and under the conditions given, diffusional hindrance in the gel phase of the intermediate oxaloacetate, which is present in rate-limiting concentrations, is the dominant cause of the observed higher efficiency in immobilized systems.

Citrate (si)-Synthase↗
PubMed1977

Thermometric enzyme linked immunosorbent assay: TELISA.

A new method, thermometric enzyme linked immunosorbent assay (TELISA), for the assay of endogenous and exogenous compounds in biological fluids is described. It is based on the previously described enzyme linked immunosorbent assay technique, ELISA, but utilizes enzymic heat formation which is measured in an enzyme thermistor unit. In the model system studied determination of human serum albumin down to a concentration of 10(-10) M (5 ng/ml) was achieved, with both normal and catalase labelled human serum albumin competing for the binding sites on the immunosorbent, which was rabbit antihuman serum albumin immobilized onto Sepharose CL-4B.

Catalase↗