Homogeneous activity test for determining enzymatic reactions

A method of quantitative determination of an enzyme modulator in a sample, wherein the method comprises the following steps:

• a) preparing and incubating a reaction mixture containing:
• (i) the sample including an unknown amount of the enzyme modulator,
• (ii) a known amount of an enzyme, whose activity can be influenced directly or indirectly by the modulator of enzyme activity to be determined,
• (iii) a substrate, which can be bound and modified by the enzyme, and
• (iv) a first and a second component of a signal-forming system, where the first component of the signal-forming system is or will become associated with the substrate and where the second component of the signal-forming system is associated with the enzyme, where the signal-forming system is such that a detectable signal is only produced if the first and the second component of the signal-forming system are brought spatially close to one another by binding of the enzyme to the substrate,
• b) measuring the signal, which is correlated with the activity of the enzyme modulator in the sample;
• and
• c) determining a concentration of the enzyme modulator based on the measured signal.