The living organism is like a well-maintained chemical
factory: a number of organic compounds are incessantly
produced and degraded, while various inorganic materials—non-carbon
compounds, metals, and minerals-are consumed, to keep
the system alive. Almost all chemical reactions in this
factory are catalyzed by protein molecules called enzymes.
As catalysts, enzymes speed up enormously (10-billion-fold)
the rate of specific biochemical reactions.
Enzymes are thus the key to understanding "metabolism,"
which is a highly integrated and regulated process of
biochemical reactions. This process is usually manifest
in a sequence of multiple reactions, rather than of
a single one, to form a "metabolic
pathway," and survival of an organism is
possible only within the narrow limits of "metabolic
regulation." Therefore, the two main goals of biochemists
studying metabolism are: (1) to map out metabolic pathways
by identifying important intermediates—substances
that are produced or used in the sequence of reactions
but are not considered final products—and isolating
the enzymes involved; and (2) to elucidate the ways
in which biochemical reactions are regulated.
Thressa and Earl have explored the metabolism of fatty
acids, amino acids, and proteins, taking advantage of
enzymes extracted from both bacterial and mammalian
cells. At NIH, they have always been allowed to choose
their own research topics, and often, their keen attention
to unexpected experimental results has paid off with
important discoveries leading to new fields of study.
To those looking for a promising research subject, their
advice is simple and direct: "Follow your nose!"
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