Harold Edwin Umbarger (17 July 1921, Shelby, Ohio – 15 November 1999, Carmel, Indiana) was an American bacteriologist and biochemist.
[1] His doctoral thesis, supervised by J. Howard Mueller,[3] is entitled Studies on the Interactions Involved in the Biosynthetic Mechanisms of Isoleucine and Valine in Escherichia Coli.
He is perhaps best known as the co-discoverer, with Edward A. Adelberg in 1953, of feedback inhibition in the metabolism of valine and isoleucine.
[2][6] Feedback inhibition in biochemistry had been reported in an almost unknown paper a decade earlier by Zacharias Dische.
[7][8] H(arold) Edwin Umbarger had a major role in defining the pathways that living organisms employ to produce branched-chain amino acids (L-leucine, L-isoleucine, and L-valine), which are required in all proteins.