Pardee, Arthur Beck (1921– )

US biochemist who discovered that enzymes can be inhibited by the final product of the reaction they catalyse (trigger); a regulatory strategy used by cells, called feedback inhibition.

Enzyme research Pardee worked on many aspects of how cells control their own processes, especially those involving enzymes. For example, Pardee worked with John Gerhart on the enzyme aspartate transcarbamoylase, an enzyme that catalyses the formation of N-carbamoylaspartate from aspartate and carbamoyl phosphate. This reaction is the first step in the biosynthesis of the pyrimidines cytidine and thymidine, which are necessary substrates for the synthesis of DNA.

Pardee and Gerhardt discovered that the aspartate transcarbamoylase enzyme, which they purified from the bacterium Escherichia coli, is inhibited by the end product of the biosynthetic pathway, known as cytidine triphosphate. This process is in effect a control mechanism that prevents N-carbamoylaspartate and subsequent intermediates in the pathway from being produced when the final product is abundant.

Life Pardee was born in Chicago, Illinois, and was educated at the University of California, Berkeley, where he worked until 1961. He was then appointed to a staff position at Princeton University and subsequently became professor of Pharmacology at Harvard Medical School in Boston 1975.

Pardee and Gerhart also discovered that the binding of the aspartate and carbamoyl phosphate to the aspartate transcarbamoylase enzyme is cooperative and that the enzyme is activated by adenosine triphosphate (ATP). ATP is a source of energy within cells and activation of the enzyme by this molecule serves to signal that there is sufficient energy available for DNA replication.