The real-time mass spectrometry (MS) systems have become robust and flexible techniques for enzyme activity, inhibition, and reaction processes and these processes can be monitored very sensitively and accurately. Regulation of enzymatic reactions and inhibitor characteristics of third molecules can be studied in detail with the help of this system. Clearly arranged experimental screening of single enzymes or multiplexed enzymes may be extended to more complex enzymatic systems and more realistic conditions, and thus to a more ambitious reaction compartment. The systematic and automated use of real-time MS will allow the research of complex molecular research fields. These analytical techniques with their bioanalytical background will extend into other research fields.