Biology Reference
In-Depth Information
asserting that, in contradiction with molecular biology and
genetic determinism, biological organisation does not arise from
the properties of molecules, but from cells as a whole.
A large amount of work has been done since the beginning of molec-
ular biology research to isolate stereospecific proteins. A great many
molecules have been characterised, such as the transcription factors
involved in regulating gene expression and the signals permitting the
transfer of information. These discoveries have resulted in major
progress, yet at the same time, a problem has arisen. When the
interactions of these proteins were analysed, instead of finding sin-
gle or a well-defined limited number of interactions, it came to light
that they do not exhibit the character of specificity expected, but on
the contrary, are conducive to a great variety of interactions. Many
proteins can interact with a large number, several tens, or even hun-
dreds, of partner molecules, generating an immense number of pos-
sible combinations. This is confirmed for the proteins implicated in
all biological phenomena and there are countless cases of molecular
non-specificity described in the literature. It is not our aim here to
carry out an exhaustive review, which would be impossible, but to
illustrate it using a few examples from the major areas of cell phys-
iology, concentrating on the signalling and regulation of gene expres-
sion. We will also analyse the causes of this non-specificity and its
consequences for a theory of biological organisation.
4.1
The non-specificity of biological molecules
4.1.1
Non-specificity in metabolism
The precision of biological processes relies for the most part on the
precision of enzyme reactions, yet there are many examples of non-
specificity in this area. Non-mutated enzymes can act on many sub-
strates, which may be exogenous substrates, as in the case of human
carboxylesterase 1. This enzyme is known for metabolising heroin
