. Biological order. Biology. THE FUNCTIONAL ORDER OPERON structural genes reguloting gene operator. L^^' enzyme forming systems Qd O/i Oy 6^ enzymes { 1 ' -^3 V 1 >2 / \ specific i nhibition of activity >tryptoc Figure 23. Control of the Activity and Synthesis of "Tryptophan ; The activity of the systems of enzymes involved in the synthesis of tryptophan (tryptophan zymon) is under a dual control. 1. The activity of the first enzyme is specifically inhibited by tryptophan, the end product of the tryptophan zymon activity. 2. The synthesis of the tryptophan zymon is
. Biological order. Biology. THE FUNCTIONAL ORDER OPERON structural genes reguloting gene operator. L^^' enzyme forming systems Qd O/i Oy 6^ enzymes { 1 ' -^3 V 1 >2 / \ specific i nhibition of activity >tryptoc Figure 23. Control of the Activity and Synthesis of "Tryptophan ; The activity of the systems of enzymes involved in the synthesis of tryptophan (tryptophan zymon) is under a dual control. 1. The activity of the first enzyme is specifically inhibited by tryptophan, the end product of the tryptophan zymon activity. 2. The synthesis of the tryptophan zymon is specifically inhibited by a repressor. The repressor is the result of the interaction of an aporepressor produced by a regulating gene and of tryptophan, which is a corepressor. The yet-hypothetical operator is in position go in the absence of repressor and is switched to stop by the repressor. The term zyvion is proposed to save time and money. Zymons belong to two categories: anazymons, which are responsible for anabolism, that is, syn- theses; and catazymons, which deal with catabolism or breakdown. The system considered here is the tryptophan anazymon, whereas /3-galactoside permease and /3-galactosidase constitute the lactose catazymon. bacterium synthesizes an excess of tryptophan, either because of a surplus of enzymes or because of a relative deficiency in the tryp- tophan consumption. The substance in excess, tryptophan, enters the constitution of a repressor. The operator, normally in position go, receives the signal stop. Tryptophan, the end product of a chain of enzymes, stops the synthesis of these enzymes. This is a true [59]. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Lwoff, André, 1902-. Cambridge, M. I. T. Press
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