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
<signed>
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.
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