ABSTRACT
In vitro enzyme systems are used as diagnostic aids in medical laboratories to determine blood constituents and activities of catalytic enzymes. The enzyme tests which are introduced in the following pages are based on the specific inhibition of the enzymatic reaction by single substances or specific groups of substances. The three tests described — acetylcholinesterase inhibition test, aldehyde dehydrogenase inhibition test, and urease inhibition test — can be used as screening tests in aquatic systems. Alteration of enzymatic activities determined by an in vivo test system — for example, the direct determination of enzyme activities of a microbial population in water samples — can be used to identify toxic effects in the ecosystem. The inhibition tests using enzymes in vitro indicate the effects of samples of unknown composition. In most cases the effect on the enzyme is an inhibition of the enzymatic activity.
