Allostérikus

Allostérikus, or allosteric, regulation refers to regulatory mechanisms in proteins whereby binding of a molecule at a site distinct from the active or catalytic site induces a functional change in the protein. This type of regulation enables cells to modulate enzyme activity in response to metabolic conditions and signaling events without covalent modification of the enzyme. Allosteric effects can increase or decrease substrate affinity and/or alter catalytic turnover.

Most allosteric regulation involves multimeric proteins with quaternary structure; effector molecules bind to allosteric sites, often stabilizing alternate conformations, commonly described as tense (T) and relaxed (R) states. Two classic models explain these changes: the concerted model (MWC), in which all subunits switch state together, and the sequential model (KNF), where ligand binding induces gradual conformational changes in subunits.

Examples include hemoglobin, which displays positive cooperativity in oxygen binding; 2,3-bisphosphoglycerate lowers O2 affinity by binding to deoxygenated Hb. Enzymes such as aspartate transcarbamoylase (ATCase) are inhibited by CTP and activated by ATP; phosphofructokinase-1 is regulated by ATP, ADP, AMP, and fructose-2,6-bisphosphate. Allosteric regulation is also central to many signaling receptors and metabolic pathways.

Physiological significance includes rapid, tunable control of metabolic flux and signal transduction. Allosteric drugs and modulators target regulatory sites to fine-tune activity, potentially offering greater specificity and reversible control compared with active-site inhibitors.

The term derives from Greek allos "other" and stereos "shape". The concept was formalized in the 1960s by Monod, Wyman, and Changeux and remains a foundational principle in biochemistry, pharmacology, and systems biology.