CHEMICAL MODELS OF ENZYMES - New Trends in Enzyme Catalysis and Biomimetic Chemical Reactions - page 172

CHAPTER 6
CHEMICAL MODELS OF ENZYMES
6.1. General principles
Outstanding catalytic and regulator properties of enzymes, which catalyze various
chemical reactions with high rates, specificity and selectivity in mild conditions (ambient
temperature, normal pressure, neutral aqua media) have long been of interest to
chemists. A greater knowledge of the principles of the structure and mechanism of
enzymes and the realization of these principles in chemistry would signify a new
decisive step in the development of the theory of kinetics and catalysis and its
application in industry (Shilov, 1997; Fersht, 1999, Groves, 1985, 2000; Silverman,
2000; Diekmann et.al., 2002)
The terms “mimicking enzymatic processes” or “chemical models of enzymes” have
no monosemantic and exact definitions. In some cases mimicking involves preceding a
specific fast chemical reaction catalyzed by an enzyme in mild conditions. In other
cases, attempts to construct chemical structures similar to an enzyme active site and to
imitate different steps of an enzymatic process are made. Depending on the knowledge
of the detailed structure and action mechanism of a target enzyme, starting positions of
chemist are also diverse.
At present, the following general steps of mimicking enzymatic processes may be
formulated.
1. Previous detailed analysis of existing data on the structure and action mechanism
of an enzyme, together with the experience and chemical intuition of the investigator,
allow the composition a realistic working program which could provide optimal
conditions for each stage of the enzymatic processes.
2. One must choose of basic (primary) catalytic groups directly involved in the
catalytic process. These groups may be nucleophilic and electrophilic reagents, general
acids and bases, complexes of transition metals of a given valence, etc. It is necessary to
emphasize that the chemical reactivity of these reagents, as well as the activity of
correspondent catalytical groups in the active sites of enzymes, have to be optimal to
provide smooth thermodynamic relief in all steps of the process.
3. Selection of secondary groups, which can regulate the reactivity of the attacking
groups. For instance, adjacent basic imidazol or carboxylate can strengthen nucleophilic
properties of a hydroxyl or acid groups can assist in the reactions of electroplic reagants.
For helping along redox processes with participation of transition metals, adjacent acid
and basic charged groups can be useful. At multi-electron processes, the presence of
transition metal clusters in the vicinity of primary metal atoms plays a key role.
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