MULTIMODULATION OF ENZYME ACTIVITY. PHYSIOLOGICAL SIGNIFICANCE AND EVOLUTIONARY ORIGIN

摘要: ABSTRACT Knowledge of specific mechanisms regulation enzyme activity has increased within less than 25 years from essentially zero to a rich variety, that in some cases reaches bewildering multiplicity. Such multiplicity presumptive regulatory effects makes particularly pressing the question physiological significance multimodulation activity, trying sort out facts artifacts, and biologically relevant vitro curiosities. The basic type mechanism is hete rotropic allosteric regulation, frequently accompanied by one or more other types mechanisms: homo-tropic cooperativity metabolic interconversion. Multiple heterotropic may range independent strongly concerted conditioned, with activation being based on counteraction an inhibition. A critical examination phosphofructokinases indicates over 20 different reported effectors, about 8, involving as many sites, seem be significant for most eukaryotic organisms. Pyruvate kinase L 5 physiologically modulation its activity. Some multimodulated enzymes are briefly discussed. An analogy principle formulated basis comparative biochemistry. In general, highly sophisticated integrators signals. fact have single kind subunit, them half dozen these subunit size not greater average non-regulatory enzymes, suggests many, perhaps even arose mutational development new sites. It argued must very old: 1 billion years.