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IN MEMORIAM

ESMOND E. SNELL


Esmond Emerson Snell, one of the outstanding biochemists of the 20th century, died in Boulder, Colorado, of prostate cancer and congestive heart failure at the age of 89 on December 9, 2003, six days after the death of his wife, Mary. He was recognized nationally and internationally for his pioneering research on vitamins and the chemistry of their actions. Especially noteworthy was his development of microbiological assays for the identification and isolation of factors essential for animal nutrition and the discovery of two new forms of vitamin B6, pyridoxal and pyridoxamine, and the elucidation of their catalytic mechanism.

Esmond was born September 22, 1914, in Salt Lake City to Hedwig Emma Ludwig and Huber C. Snell. His parents met while serving as Mormon missionaries, married in 1905, and had five children. Esmond and his siblings attended Provo High School and Brigham Young University. After receiving his B.A. in chemistry in 1935, Esmond received a $400 scholarship from the Wisconsin Alumni Research Foundation and headed to the University of Wisconsin in Madison. There he earned an M.A. in biochemistry in 1936 and a Ph.D. in biochemistry in 1938. After moving to The University of Texas at Austin, Esmond married Mary Caroline Terrill, a senior chemistry major, on March 15, 1941. Mary and Esmond had four children: Richard, Allan, Margaret, and Esmond Jr., who was killed in action in Vietnam in 1968.

Esmond’s long and distinguished academic career began in 1939 at The University of Texas at Austin as a postdoctoral research associate with Roger J. Williams. He was appointed assistant professor of chemistry in 1941 and associate professor in 1943. He returned to the University of Wisconsin in 1945 as associate professor of biochemistry. Subsequently, he served as professor of biochemistry at the University of Wisconsin (1947-1951), professor of chemistry at The University of Texas at Austin (1951-56), and professor of biochemistry at the University of California, Berkeley (1956-1976) including chairmanship of the Department of Biochemistry (1956-1962). He returned to The University of Texas at Austin in 1976 as professor of both microbiology and chemistry and was chairman of the Department of Microbiology from 1976-1980. He became Ashbel Smith Professor of Chemistry in 1980 and professor emeritus in 1990. During his long and productive career, he trained more than thirty Ph.D. students, had more than forty postdoctoral fellows and senior associates, and published about 400 scientific papers and reviews. He received numerous awards, including the Eli Lilly Award in Bacteriology and Immunology from the Society of American Bacteriologists (1945), the Mead-Johnson Vitamin B Complex Award from the American Institute of Nutrition (1946), the Osborne-Mendel Award from the American Institute of Nutrition (1951), the Kenneth A. Spencer Award from the American Chemical Society (1974), and the William C. Rose Award from the American Society of Biological Chemists (1985). He was elected to the National Academy of Sciences in 1955 and the American Academy of Arts and Sciences in 1962. He received an Honorary Doctor of Science from the University of Wisconsin in 1982. He was a fellow of the American Association for the Advancement of Science and the American Institute of Nutrition, a former chairman of the Division of Biological Chemistry of the American Chemical Society, and a former president of the American Society of Biological Chemists. He served on many national and international committees and editorial and advisory boards. He was editor of the Annual Review of Biochemistry from 1969-1983.

Esmond has described his personal odyssey in the paper, “From Bacterial Nutrition to Enzyme Structure.” (Annual Review of Biochemistry 62:1-27 (1993)). His thesis project at the University of Wisconsin was to identify growth factors for lactic acid bacteria, which required complex media for growth. The experimental approach was to start with a simple medium and to determine what supplements were necessary for growth. This and later work resulted in the discovery of several vitamins and related substances, in the development of microbiological assays for following the purification of these substances, and in determining their concentration in nature. He published an assay for riboflavin in 1939, which was the first microbiological assay for a vitamin. This served as a prototype assay for each of the B vitamins. The method gave results comparable to those obtained by a much more lengthy, cumbersome, and expensive rat assay. The use of microbiological assays instead of animal assays for vitamins has resulted in untold savings in time and money. While at the University of Wisconsin, Esmond also published microbiological assays for pantothenic acid and nicotinic acid.

At The University of Texas in the early 1940s, Esmond, together with Hershel Mitchell and Roger Williams, purified a growth factor from four tons of spinach that was named “folic acid.” The report of this work has been called “A Nutrition Classic.” In the course of investigations of microbiological assays for vitamin B6 with different microorganisms, Esmond and his colleagues discovered two new forms of vitamin B6, subsequently identified as an aldehyde and an amino form, and named pyridoxal and pyridoxamine, respectively. While investigating the natural forms of vitamin B6, Esmond’s group found that pyridoxal and pyridoxamine were readily interconverted by a fully reversible, non-enzymatic transamination reaction with glutamate and a-ketoglutarate. Further investigation showed that pyridoxal catalyzed a series of nonenzymatic reactions of amino acids that simulated closely the corresponding reactions catalyzed in living organisms by pyridoxal phosphate-dependent reactions. Detailed studies of these model, nonenzymatic reactions led to the proposal in 1954 of a general mechanism for the action of vitamin B6-dependent enzymes. It was a unique contribution to the field of enzymology because it provided a verifying mechanism to a wide range of apparently unrelated transfer or elimination reactions. In further studies of vitamin B6-dependent enzymes, Esmond’s group discovered another closely related class of enzymes, the pyruvoyl enzymes. Histidine decarboxylase purified from Lactobacillus 30a, a Gram-positive organism, did not contain pyridoxal phosphate, as expected, but instead contained a covalently bound pyruvoyl prosthetic group. This group was shown to participate as a Schiff’s base in the catalysis of decarboxylation and to arise from a specific serine residue in the proenzyme by a previously unobserved, intrachain, non-hyrolytic cleavage reaction. Peptide chain cleavage is coupled to an ab-elimination reaction to form an active enzyme that contains two chains, one of which has an N-terminal pyruvoyl residue. Several other enzymes have been found subsequently to have a pyruvoyl prosthetic group.

In addition to his scientific achievements, Esmond played a central role as a good citizen of the biological community and was widely regarded as a gentle, unassuming person. He served on many national and international committees and editorial advisory boards. Esmond was also highly regarded as a teacher and mentor. Typical were these comments by former graduate students: “He treated us all with respect, even when work was not going well. We all liked Es.” And, “Esmond took me under his wing and taught me how to be a professional scientist. Without question, he has been the one person who has made the most impact on me and my life as a person and a scientist. He and Mary became my surrogate parents during my years as a graduate student.” Esmond had a series of Japanese scientists in his laboratory at the University of California, Berkeley. After a lecture during a sabbatical stay at Osaka University in 1971, a student asked Esmond to write on a fancy paperboard a message for the students. Many Japanese and American scientists have copies of this statement, which summarizes Esmond’s philosophy of science. He wrote,
Hard work on interesting problems is enjoyable and preferable to aimless wasting of leisure time. It may also lead to unexpected findings that give insights into important related problems. Such unexpected findings–sometimes called “luck”–frequently happen to the active researcher, but only rarely to those who prefer talk to study and work. So one should study and work hard, on interesting problems of any nature, with the purpose of explaining nature and helping others.



<signed>

Larry R. Faulkner, President
The University of Texas at Austin


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Sue Alexander Greninger, Secretary
The General Faculty





This memorial resolution was prepared by a special committee consisting of Professor Emeritus Lester J. Reed (chair) and Professors Marvin L. Hackert and Ian J. Molineux.