[Regulation processes in biological systems. I. General principles and enzymatic control mechanisms]

A property, characteristic of all living organisms, is the ability to adapt their metabolism to changes of environment. Such an adaptation, i.e. a regulation of metabolism, is made possible not only by nervous and hormonal mechanisms, but it is also caused by the cooperation of enzymes and enzyme systems localized in different cell areas and may called "enzymic regulations". Enzymes are functional units of complex chemical systems. Although present knowledge in this area is primitive, it is already apparent that the properties of regulatory enzymes are very precisely tailored to the needs of the cells in which they occur. The kinetic behaviour of an enzyme can be rationally interpreted only in terms of metabolic function and the structural features of an enzyme molecule are only the means by which this behaviour is attained. Each enzyme has evolved in the context of a metabolizing cell and the progress in understanding the kinetic and structural properties of enzymes will be aided by progress toward understanding the interactions in which that enzyme participates in the living cell. It is certain that we have only just begun to comprehend the ways in which the enzymes interact to produce a stable, yet flexible and responsive metabolic unit.