The effects of variations of substrate concentration on the velocity of an enzymatic reaction. We may only add that in some cases, variations of substrate or co-substrate concentration [S] can exert important effects on the metabolism by permitting either the synthesis, or on the contrary the degradation of a substance X, or by determining the metabolic pathway in which a [...]
In connection with the tryptophan operon, that an excess of tryptophan can cause a repression of the genes of this operon, leading to an arrest of the synthesis of the enzymes required for the formation of tryptophan. Beside this possibility of repression, there is very often feedback inhibition, i.e. the possibility for an essential metabolite (amino acid, nucleotide, etc.), which [...]
The synthesis of enzymes - or more generally, the synthesis of proteins — implies the incorporation of amino acids in an order dictated by the genetic information. Control of the Expression of Genes at the Level of Transcription: In addition to the adaptation mechanisms operating in the cells in response to changes in environmental conditions, cellular differentiation and developÂment imply [...]