Michaelis, Leonor (1875-1949)

German-born, US biochemist who derived a mathematical model to describe the kinetics of how enzymes catalyse (trigger) reactions. The work of Michaelis and German scientist Maude Menton enabled several subsequent generations of biochemists to correctly assess the nature and efficiency of the key, enzyme-driven steps in cell metabolism.

Although Michaelis published many papers on the measurement of pH using various indicators, including early versions of the pH electrode, he is best known for his work on the physical properties and activities of enzymes. He worked for many years on pepsin, a digestive enzyme normally produced by the stomach. His joint work with Menton led to the formulation of a general, mathematical model to describe the kinetics of how enzymes catalyse reactions, called the Michaelis-Menton equation, 1913.

In their mathematical calculations they correctly assumed that an enzyme works by rapidly and reversibly binding to a specific molecule (called the substrate) to form an enzyme-substrate complex, triggering a reaction that generates a product molecule. Once the reaction has occurred the enzyme is released unchanged. Michaelis and Menton then correlated the speed of the enzymatic reaction with the concentrations of both the enzyme and the substrate.

Michaelis was born in Berlin, where he later became a professor 1908. He took up a staff position in Japan 1922, and then at Johns Hopkins University 1926-29 and Rockefeller University 1929-40 in the USA.