Enzyme action, discovery of the

Enzyme action, discovery of the mechanisms of, 1947-1963, 21, 1 Equilibrating systems, isotope effects on nmr spectra of, 23, 63 Equilibrium constants, N.M.R. measurements of, as a function of temperature, 3,187 Ester hydrolysis, general base and nucleophilic catalysis, 5, 237 Exchange reactions, hydrogen isotope, of organic compounds in liquid ammonia, 1, 156... 

Riboflavin was first isolated from whey in 1879 by Blyth, and the structure was determined by Kuhn and coworkers in 1933. For the structure determination, this group isolated 30 mg of pure riboflavin from the whites of about 10,000 eggs. The discovery of the actions of riboflavin in biological systems arose from the work of Otto Warburg in Germany and Hugo Theorell in Sweden, both of whom identified yellow substances bound to a yeast enzyme involved in the oxidation of pyridine nucleotides. Theorell showed that riboflavin 5 -phosphate was the source of the yellow color in this old yellow enzyme. By 1938, Warburg had identified FAD, the second common form of riboflavin, as the coenzyme in D-amino acid oxidase, another yellow protein. Riboflavin deficiencies are not at all common. Humans require only about 2 mg per day, and the vitamin is prevalent in many foods. This vitamin... 

The discovery of the antiulcer activity of H2 antihistamine antagonists has revolutionized the treatment of that disease. A benzimidazole. Omeprazole (55), inhibits gastric secretion and subsequent ulcer formation by a quite different mechanism. Studies at the molecular level suggest that this compound inhibits K /H dependent ATPase and consequently shuts down the proton pumping action of this enzyme system. 

Another of Conant s students was Frank Westheimer (b. 1912), who, after postdoctoral work with Hammett at Columbia, held a post at the University of Chicago (1936-1954) and then returned to Harvard. Westheimer worked in several areas of physical organic chemistry and engaged in other chemistry-based activities, as revealed in an interview conducted in 1995 by Istvan Hargittai.233 For much of his career, Westheimer was essentially a physical organic chemist working in biochemistry and he has himself written reflectively on the discovery of the mechanisms of enzyme action over the period 1947-1963234 and on the application of physical organic chemistry to biochemical problems.235 Westheimer has also contributed, as Tetrahedron Perspective Number 4, an article on Coincidences, decarboxylation, and electrostatic effects , which, he writes, ...allows me to review some of my past .236... 

Directive effects in aromatic substitution, a quantitative treatment of, 1, 35 Directive effects in gas-phase radical addition reactions, 16, 51 Discovery of the mechanisms of enzyme action, 1947-1963, 21, 1 Displacement reactions, gas-phase nucleophilic, 21, 197... 

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