Mary Lilias Christian Bernheim (née Hare; 28 June 1902 – 19 November 1997) was a British biochemist best known for her discovery of the enzyme tyramine oxidase, which was later renamed as monoamine oxidase. Bernheim discovered the enzyme system of tyramine oxidase during her doctorate research at the University of Cambridge in 1928, and her research has been referred to as "one of the seminal discoveries in twentieth century neurobiology". Early life and education Bernheim was born under the name Mary Lilias Christian Hare in Gloucester, England on 28 June 1902. However, she was referred to as "Molly" by those around her. As a child, Bernheim was raised in India. She obtained higher degrees of BA, MA, and PhD from the University of Cambridge in England. After finishing her undergraduate, Bernheim received the Bathurst Studentship to work on her PhD research in the Department of Biochemistry at the Newnham College of the University of Cambridge. Discovery of monoamine oxidase As a doctoral student, Bernheim was aware of the limited research which had been conducted on the catabolism of tyramine, a naturally occurring monoamine compound obtained from the amino acid tyrosine. Keeping in mind the availability of newly enhanced techniques for the analysis of oxidative processes, she decided to study the manner in which the addition of tyramine affected oxygen uptake in tissues. During the course of her work, Bernheim used rabbit liver extracts and obtained the enzyme by adding kaolin to the liver extracts at pH 6.5. Following this, crude tyramine was procured by heating tyrosine in the presence of the catalyst diphenylamine. The extracted enzyme was added to tyramine, in the presence of water and buffer, and the Barcroft technique was used to observe the amount of oxygen consumed by tyramine. She discovered that the oxidation of tyramine did take place, with the observation that one atom of oxygen was absorbed per molecule of tyramine present. This observation indicated the presence of an enzyme system within the studied liver extracts, which Bernheim named tyramine oxidase, since it was involved in the oxidation of tyramine. In addition to the discovery of the enzyme system, Bernheim observed several unique properties of the tyramine oxidase system. She noted that the methylene blue dye used in the experiment was not reduced. This observation indicated that the tyramine oxidase system, unlike other enzyme systems, was not able to use the dye as a hydrogen