Sensitive assay of creatine kinase isoenzymes in human serum using M subunit inhibiting antibody and firefly luciferase

Applications of bioluminescence in biotechnology and beyond

Bioluminescent probes have hugely benefited from the input of synthetic chemistry and protein engineering. Here we review the latest applications of these probes in biotechnology and beyond, with an eye on current limitations and future directions.

Optimization of the firefly luciferase reaction for analytical purposes

The optimization of assays has two purposes: (1) to increase the sensitivity of the assay so that low levels of the analyte can be determined; and (2) to prevent small changes of the reaction conditions from having a large impact on the outcome of the assay. The two purposes are usually equally important, as has been recognized in well-established branches of analytical chemistry, such as clinical chemistry. The firefly luciferase reaction can be used for many types of assays. The way to optimize these assays is not trivial, as there are many parameters to consider. Furthermore, as there are now several types of recombinant luciferases available, one has to decide which is the most suitable for each individual assay. The optimization is influenced by the conditions and requirements under which the assay is performed. Special attention is given to ways to calibrate assays. Examples on optimization are mainly taken from the author's own work during 40 years using assays based on the firefly luciferase reaction.

Creatine kinase and recurrent myocardial infarction

Daily measurements of serum creatine kinase (CK) activity have been performed in 31 patients during hospitalization for acute myocardial infarction (MI). If CK was raised, isoenzyme B was analysed as well. In this way one probable silent MI and another two overt MIs were diagnosed. MI recurred within three months after discharge in another five patients. None of these eight patients showed even small increases in the daily CK activity when in hospital. This study does not support the concept that reinfarction is a stepwise damage of the myocardium.

Membrane cholesterol is required for activity of Vibrio vulnificus cytolysin

Vibrio vulnificus cytolysin (VVC) forms a pore in the plasma membrane and induces cytolysis of various cells including erythrocytes, neutrophil and endothelial cells. The cytolytic activity of VVC is inhibited by exogenously added cholesterol, suggesting that membrane cholesterol might be required for VVC cytolytic activity. However, there is no direct evidence that membrane cholesterol is involved in VVC-induced cytolysis. Herein we demonstrate that membrane cholesterol is required for binding of VVC to the plasma membrane. Membrane cholesterol depletion with methyl-beta-cyclodextrin inhibited VVC-induced K(+) release, 2-deoxy glucose release and Ca(2+) influx, which are indicators of VVC pore formation. The cholesterol depletion-induced blockage of VVC cytolysis was due to the inhibition of VVC binding to membrane. These findings suggest that interaction with cholesterol is required for activity of VVC.

Cytotoxic mechanism of Vibrio vulnificus cytolysin in CPAE cells

Vibrio vulnificus is an estuarian bacterium that causes septicemia and serious wound infection. The cytolysin, one of the important virulence determinants in V. vulnificus infection, has been reported to have lethal activity primarily by increasing pulmonary vascular permeability. In the present study, we investigated the cytotoxic mechanism of V. vulnificus cytolysin in cultured pulmonary artery endothelial (CPAE) cells, which are possible target cells of cytolysin in vivo. V. vulnificus cytolysin caused the CPAE cell damages with elevation of the cytosolic free Ca2+, DNA fragmentation, and decrease of the cellular NAD+ and ATP level. These cytotoxic effects of V. vulnificus cytolysin were prevented by EGTA and aminobenzamide, but were not affected by verapamil or catalase. These results indicate that the elevation of cytosolic free Ca2+ induced by V. vulnificus cytolysin causes the increase of DNA fragmentation and the damaged DNA activates nuclear poly(ADP-ribose) synthetase, which depletes the cellular NAD+ and ATP, resulting in cell death.

Bioluminescent assay of creatine kinase activity using immobilized firefly extract

A bioluminescent method has been developed for creatine kinase (CK) assay using immobilized firefly extract containing the bioluminescent coimmobilized system: adenylate kinase + luciferase. ADP for the reaction with CK was produced from the initial mixture of AMP and ATP. The ATP formed in the reaction with CK was quantified using firefly luciferase. The lowest detection limit for CK activity was 0.5 +/- 0.2 U/liter in the sample. A linear range of the determined CK activities was 0.5-1000 U/liter. The correlation coefficient between the bioluminescent and spectrophotometric methods was 0.981 (n = 40). The use of immobilized firefly extract for analysis has been shown to be advantageous compared to soluble enzyme.

Chemiluminescence: applications for the clinical laboratory

The chemical features and applications of chemiluminescence are reviewed, with special attention to bacterial and firefly bioluminescence and to uses of chemiluminescence in direct substrate assays, enzyme assays, solid-phase reactions, and immunoassays.

A bioluminescent assay for enolase (EC 4.2.1.11) activity in human serum and cerebrospinal fluid

A simple method is described for the measurement of enolase enzyme activity in human serum and in unconcentrated cerebrospinal fluid. The enzyme is measured by a bioluminescent assay, making use of the luciferine/luciferase system. The method is very suitable for use in clinical chemical laboratories. The Michaelis-Menten constants of three enolase isozyme forms have been measured. Data concerning the in vitro stability at 37 degrees C of alfa-alfa, alfa-gamma and gamma-gamma enolase in cerebrospinal fluid are presented. The gamma-gamma form is the most stable enolase form under these conditions. Preliminary data from a clinical study about the diagnostic significance of the enzyme indicate that evident elevations in cerebrospinal fluid enolase levels can be seen in patients from neurological wards. There is a poor correlation between total creatine kinase and enolase cerebrospinal fluid levels.

A sensitive assay for creatine kinase in serum samples dried on paper: enhanced thermal stability of the dried enzyme

A new bioluminescent creatine kinase (CK) assay using purified luciferase was used to analyse CK activity in serum samples dried on filter paper. Enzyme activity was preserved for over 1 wk on paper stored at room temperature. At 60 degrees C, CK activity in liquid serum samples was rapidly inactivated, but the activity of enzyme stored on paper was preserved for at least 2 days.

Bioluminescent assay of total and brain-specific creatine kinase activity in cerebrospinal fluid

A bioluminescent assay based on the firefly luciferase reaction has been used for determination of creatine kinase activity in CSF. Activities as low as 0.1 U/L can be measured. The coefficient of variation at an activity level of 0.3-0.4 U/L was between 5 and 6%. The assay conditions optimized for serum specimens can be used for CSF. The adenylate kinase activity is almost completely inhibited, which simplifies the procedure. The creatine kinase/(CK) isoenzyme distribution was obtained using the bioluminescent assay in combination with immunoinhibition or ion exchange chromatography. All specimens contained both MM and BB activity, but no MB was found. The study indicates that the bioluminescent assay is useful in the determination of CK isoenzymes in CSF. The clinical importance of the observed CK levels will be reported in a separate communication.