Enzyme-selective detector systems for high-pressure liquid chromatography

Lactate dehydrogenase isoenzymes

The analytical procedures for LD isoenzymes include electrophoresis, chromatography, immunochemical and kinetic methods. Electrophoretic methods are generally preferred because the resulting patterns are directly observable and all five isoenzymes are resolved in a single procedure. Chromatographic methods, with the introduction of HPLC, have recently been perfected in terms of speed, resolution, precision and accuracy. Immunochemical methods and kinetic methods are attractive because of their speed and simplicity. Therefore, the latter methods are used mainly for assaying acute myocardial infarction, where generally the determination of LD-1 and LD-2 is sufficient. In all other instances, however, electrophoretic separation is currently preferred. Ion-exchange high-performance procedures are useful prospects, particularly in view of their velocity in comparison with electrophoresis. In general, the LD isoenzymes assay contributes considerably to diagnosis, but the results must be used with an adequate knowledge of biochemistry, physiology and the advantages and drawbacks of the different assay methods used.

Rapid separation and measurement of rat urinary kallikrein by high-performance liquid chromatography with a continuous flow enzyme detector

Rat urinary kallikrein was separated by high-performance liquid chromatography (HPLC) using an ion-exchange or gel-permeation column. Kallikrein activity was monitored continuously with peptidase or esterase activity using a post-reactor system directly adapted to HPLC. A PTFE helically coiled tube served as the enzyme reactor vessel. Four and three peaks with peptidase and esterase activity, respectively, were detected on application of normal rat urine.

Separation and measurement of isoenzymes and other proteins by high-performance liquid chromatography

We review the state-of-the-art of the separation of isoenzymes and other proteins by high-performance liquid chromatography (HPLC) and their subsequent, continuous detection and activity assay by post-column reaction (PCR). We describe the developments leading to current practice. These developments are categorized by column packings, post-column reaction detectors and applications in which specific analysis systems for isoenzymes, especially for lactate dehydrogenase (LD) and creatine kinase (CK) are discussed. Although HPLC coupled with PCR detection is well developed and in many cases is analytically superior to other isoenzyme technologies, it is not at the present used for routine clinical applications. We expect this trend to be reversed with clinical demonstration and the addition of commercially available automation.

Dual-detector-post-column reactor system for the detection of isoenzymes separated by high-performance liquid chromatography. I. Description and theory

We describe a dual-detector-post-column chromatographic reaction detector system that corrects for substances present in biological samples that interfere with the measurement of isoenzymes separated on a chromatographic column. The response observed at the detector in front of the reaction coil is mathematically dispersed, time transformed and subtracted from the detector behind the coil to produce a blank corrected chromatogram. The same computer program calculates peak areas and other chromatographic parameters such as height equivalent to a theoretical plate and retention time. In addition, we have evaluated the dispersion effects caused by various changes in our experimental system.

Dual-detector-post-column reactor system for the detection of isoenzymes separated by high-performance liquid chromatography. II. Evaluation and application to lactate dehydrogenase isoenzymes

We describe the separation of lactate dehydrogenase isoenzymes by high-performance liquid chromatography-anion-exchange columns and their quantitation by a computer-controlled, dual-detector post-column reaction system. The recoveries from the separation column were ca. 90%. The dynamic range of the system was linear over about three orders of magnitude from 3 to 1500 U/l. The coefficient of variation for isoenzyme peak areas was ca. 2%. The method is compared to the classical electrophoresis measurement and shows increased speed, resolution, precision and accuracy.

Techniques for detecting enzymes in high-performance liquid chromatography

Techniques are described for the automated detection of a series of enzymes in a high-performance liquid chromatographic system. Detection was achieved by either a direct or a coupled enzyme assay using photometric detectors. In direct detection the immediate enzymatic product was monitored. Coupled enzyme assays required additional enzyme(s) to convert the product of the primary enzyme reaction into a more easily detectable form. The efficiency of both free and immobilized coupling enzyme(s) was evaluated. The detector sensitivity could be increased three-fold by increasing the reaction temperature. This system is particularly suitable for isoenzyme profiling in biological materials.