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K Eschrich

Publications and source records attributed to K Eschrich.

63 records · Page 4Linked to original sources
PubMed1982

Transitions between alternate ATP-producing and ATP-consuming stationary states in a reconstituted enzyme system containing phosphofructokinase.

The kinetic behavior of a reconstituted eyzyme system containing purified phosphofructokinase, pyruvate kinase, adenylate kinase, and glucose 6-phosphate isomerase was investigated. Experimentally the approach is based on a stirred flow-through reactor containing gel entrapped enzymes. The experiments were performed on the basis of a mathematical model developed from the kinetic properties of the individual enzymes involved. The system is able to exhibit alternative stable stationary states for one set of experimental conditions (bistability) originating mainly from the allosteric character of the phosphofructokinase. From a functional point of view, these states are either ATP-generating or ATP-consuming. Theoretically, the appearance of alternate steady states gives rise to hysteretic behavior of the system. In fact, transitions between alternate ATP generating stationary states as well as between ATP-generating and ATP-consuming steady states were observed experimentally.

Adenosine Triphosphate↗
PubMed1981

Self-stabilization of the energy charge in a reconstituted enzyme system containing phosphofructokinase.

The self-stabilization of the energy charge and of ATP was investigated in an open reconstituted enzyme system containing phosphofructokinase, pyruvate kinase, adenylate kinase, and glucose-6-phosphate isomerase. The experiments were performed in a stirred flow-through reactor containing gel-entrapped enzymes. The dynamics of the system were analyzed theoretically by a model based on the kinetic properties of the individual enzymes. The energy charge was identified as one of the essential variables of the system. According to the theoretical prediction, homoeostasis of the energy charge was observed experimentally when either the maximal activity of phosphofructokinase, the energy charge of the influx solution of the flow rate through the reaction chamber was varied. It is shown that the efficiency of stabilization of the energy charge is related to the occurrence of alternative stationary states.

Adenylate Kinase↗
PubMed1979

Kinetic modelling of yeast phosphofructokinase.

Phosphofructokinase from baker's yeast (Saccharomyces cerevisiae) is an octameric enzyme which exhibits complex allosteric behaviour. In contrast to mammalian phosphofructokinase, the enzyme does not show association-dissociation behaviour. A systematic kinetic investigation at pH 7.2 in dependence on the substrates, fructose 6-phosphate and ATP as well as on the effectors AMP and ADP is presented. The results are interpreted in terms of a structure oriented theoretical model. Because the two state model of Monod, Wyman and Changeux proved to be insufficient for interpretation of the experimental data, it was extended to a four state model in which the basic conformations R and T of the enzyme are split into subconformations R1 and R2 as well as T1 and T2, respectively. It is assumed that fructose 6-phosphate and the adenine nucleotides influence different allosteric equilibria. The model permits a precise quantitative description of the experimental data.

Adenosine Diphosphate↗
PubMed1979

Non-linear dynamic phenomena in open reconstituted enzyme systems.

The dynamic pattern of an open reconstituted in-vitro enzyme system containing phosphofructokinase, pyruvate kinase and adenylate kinase has been investigated. The approach is experimentally based on a stirred flow-through reactor. Stationary concentrations of phosphofructokinase and pyruvate kinase are maintained by entrapment in polyacrylamide gel particles. The results fit to a theoretical model based on the initial kinetic responses of the enzymes involved. An S-shaped steady state input characteristic for fructose 6-phosphate has been experimentally obtained.

Adenosine Triphosphate↗
PubMed1978

Dynamic properties of in vitro enzyme systems containing phosphofructokinase.

The dynamic properties of a series of in vitro reaction systems with increasing complexity and containing phosphofructokinase as central enzyme have been investigated. An experimental strategy and a principal mathematical treatment was elaborated to search for the minimum requirements with respect to the enzyme composition of a reaction system for generating limit cycle behaviour. As a criterion, such models have been developed which permit experimental realization by application of a specially designed flow-through equipment. In addition to phosphofructokinase, the following enzymes have been stepwise included into the reaction systems composing the Models 1 through 6: pyruvate kinase, adenylate kinase, hexokinase, and glucose 6-phosphate isomerase. It turned out that only a minimum dynamic system containing phosphofructokinase and pyruvate kinase as well as excesses of adenylate kinase and glucose 6-phosphate isomerase for maintaining equilibrium conditions between the respective reacting species, acquires the property of limit cycle behaviour and, hence, to generate sustained self-oscillations. The approach permits to compute the region of the experimentally variable parameters (influx rates of fructose 6-phosphate and ATP, maximum rate of pyruvate kianse) for which self-oscillatory behaviour can be predicted.

Adenylate Kinase↗
PubMedDate not supplied

Peroxidase reaction as a parameter for discrimination of Streptococcus mutans and Streptococcus sobrinus.

425 strains of mutans streptococci and 12 reference strains were investigated by membrane fatty acid spectra (MFAS) and peroxidase reaction (PR) after aerobic and anaerobic incubation. 423 strains were identified as Streptococcus mutans. The remaining 2 strains were identified as Streptococcus sobrinus. The PR of 29 strains was doubtful; immediately after anaerobic incubation a negative PR changed into a slightly positive PR. To test the diagnostic value of PR the strains were additionally investigated by means of species-specific polymerase chain reactions (PCR). The species-specific PCRs were developed on the basis of the respective genes of 16S rRNA of the pathogens S. mutans and S. sobrinus. Specificity and sensitivity were tested on reference strains (n = 17) and negative control strains (n = 39). The results of this investigation showed that an anaerobic incubation regime could lead to false-positive (S. mutans) or false-negative (S. sobrinus) PR. The 425 MS strains were classified as either S. mutans (n = 420) or S. sobrinus (n = 5). The findings on the reference strains required a reclassification of S. mutans V 100 into S. sobrinus V 100. Summarising, it is possible now to differentiate strains of mutans streptococci by MFAS and PR after aerobic incubation.

Aerobiosis↗
PubMedDate not supplied

Clinical significance and neuropathology of primary MADD in C34-T and G468-T mutations of the AMPD1 gene.

OBJECTIVE: Primary myoadenylate deaminase deficiency (MADD) is probably the most frequent inborn metabolic myopathy with a prevalence of up to 2%. It is the result of mutations in the AMPDI gene, the most common of which is a C34-T transition in exon 2. The importance of the more rare mutation G468-T in exon 5 is uncertain. Primary objective was to elucidate the clinical significance of the enzyme disorder, which remains unclear since its first description in 1978. We further examined the existence of an association of MADD with other muscle disorders, such as malignant hyperthermia and rhabdomyolysis, as was suspected in earlier studies. MATERIAL AND METHODS: In a large collection of 1673 muscle biopsies that had been stored deep frozen we identified 33 cases of primary MADD, 12 of which without any other coinciding muscle diseases, by histochemical, biochemical and molecular genetic examinations. Clinical and laboratory data was collected. By additional examination of randomly chosen blood samples we identified one person carrying the rare compound heterozygosity C34-T/ G468-T, who was examined in clinical respects and a muscle biopsy was taken. RESULTS: As underlying mutation, the most common transition C34-T/C 143-T was detected in 33 cases. One patient carried the compound heterozygosity C34-T/G468-T. The overall frequency of MADD in the contingent was 1.8%. Only three patients out of 12 with isolated primary MADD suffered from muscle complaints, one of whom did not experience the typical symptoms of exercise related myalgia, muscle cramps and weakness as described by Fishbein. The patient carrying C34-T/G468-T was a fully healthy female. She had never experienced any muscle complaints. Any association with other neuromuscular disorders, if not completely ruled out, was found to be very unlikely. CONCLUSION: The results suggest that MADD itself is unlikely to be solely responsible for the manifestation of muscular symptoms. It is probable that either the loss of a compensation mechanism or coexistent disturbances in muscle metabolism which are unidentified so far are required for the emergence of complaints.

AMP Deaminase↗