Archive | Enzymes

Allosteric enzymes and enzymes that exhibit cooperative effects do not display conventional Michaelis-Menten kinetics. Figure 8-25 compares the Michaelis-Menten curves for enzymes exhibiting non­cooperativity, positive cooperativity, and negative cooperativity. The curve in Figure 8-25a shows the normal hyperbolic binding pattern exhibited by most enzymes. In this example, an 81-fold increase in sub­strate concentration is required to elevate enzyme ac­tivity from [...]

Sudden and dramatic changes in cellular activity (e.g., conduction of nerve impulses by a nerve cell or the contractions of a muscle cell) demand rapid increases (or decreases) in the cellular level of particular meta­bolic intermediates. The binding of effectors at the regulatory sites of allosteric enzymes acts to quickly increase (or de­crease) the level of enzyme activity and in [...]

The metabolism of a cell is characterized by a myriad of simultaneously occurring chemical reactions. Nearly all these reactions are catalyzed by a special class of proteins called enzymes. It has been esti­mated that the typical eukaryotic cell contains about 3000 different enzymes. In the absence of these en­zymes, most of the cellular reactions would proceed at much slower rates. [...]