Primary enzyme quantitation using substrates labeled with a second indicator enzyme. I. Elastase determination using peroxidase-labeled elastin

A versatile microassay for elastase using succinylated elastin

We have developed a rapid, versatile, and sensitive elastase assay that is based on the measurement of primary amines that are exposed due to enzymatic degradation of proteins, using succinylated elastin as the substrate for elastase. After incubation with elastase the degree of digestion is determined with trinitrobenzene sulfonic acid. The assay is rapid and sensitive, detecting elastase down to 1 ng/ml, and is linear up to enzyme concentrations of 10 microg/ml. The assay is carried out in microtiter plate wells and therefore offers the potential for assaying numerous samples of small volume. The use of succinylated elastin shows specificity for elastase over the control protease, trypsin. This assay is also versatile because it can be applied to samples such as cell culture supernatants, blood plasma, tissue biopsies, and tissue homogenates.

A sensitive assay for proteolytic activity using fluorescein-labeled gelatin coupled to Sepharose 4B as substrate

A method for the determination of proteolytic activity is described which uses fluorescein-labeled gelatin coupled to Sepharose 4B as substrate. The assay is simple and sensitive allowing detection of one nanogram of trypsin and is found suitable for the measurement of gelatinolytic activity in tissue samples.

An evaluation of fluorometric proteinase assays which employ fluorescamine

The sensitivity and utility of proteinase assays employing fluorescamine, a compound which reacts with primary amines to form a fluorescent adduct, was assessed. As little as 1 ng of purified trypsin or clostridiopeptidase A could be detected within 3 h of incubation at 37 degrees C, using casein or gelatin as substrates. Increasing the incubation period to 18 h permitted the detection of 250 pg of each enzyme. When gelled collagen was utilized as substrate, the sensitivity to clostridiopeptidase A was reduced to 2.5 ng at 3 h and 500 pg at 18 h. The techniques could be used to measure the gelatinase, caseinase, and collagenase activities of culture media conditioned by synovial tissue. The main disadvantage of this assay is its susceptibility to interference by compounds which fluoresce or quench. This, in turn, necessitates additional blanks, which may render the assay tedious.

Adsorbed soluble [3H]elastin as substrate for proteinase activity. A new microassay technique

A microassay for elastase activity has been designed. Microtubes are coated with soluble elastin substrate by passive adsorption to the tube walls. On contact with enzymes in test samples, radioactivity is released into the sample buffer, which is then transferred to vials containing scintillation fluid without further processing. Porcine pancreatic elastase (EC 3.4.21.11) is easily detected in concentrations down to 8 micrograms/litre. The interassay coefficient of variation (CV) was below 10% for values above 50 micrograms/litre. The assay is rapid, precise, economical and sensitive.

Amperometric assay for collagenase. Amplification by the use of glucose oxidase conjugated to insoluble collagen

A sensitive and rapid amperometric assay for collagenase has been developed. The substrate for the assay is glucose oxidase covalently linked to insoluble collagen with dimethylsuberimidate. The collagenase cleaves the insoluble collagen--glucose oxidase conjugate into smaller, soluble fragments that have glucose oxidase activity. That activity is proportional to the collagenase activity hydrolyzing the insoluble conjugate. In the absence of collagenase, no glucose oxidase activity is found in the soluble phase. Glucose oxidase activity was assayed by measuring amperometrically the rate at which hydrogen peroxide is produced. The kinetics follow that proposed for a soluble enzyme acting on an insoluble substrate.