Cyklázy

Cyklázy are enzymes that catalyze the formation of cyclic molecules. In biochemistry, the most prominent examples are adenylyl cyclase and guanylyl cyclase. These enzymes play crucial roles in signal transduction pathways within cells.

Adenylyl cyclase, often referred to as AC, catalyzes the conversion of adenosine triphosphate (ATP) into cyclic adenosine monophosphate (cAMP) and pyrophosphate. cAMP is a vital second messenger that mediates the effects of various hormones and neurotransmitters. It activates protein kinase A (PKA), which in turn phosphorylates numerous target proteins, leading to diverse cellular responses such as glycogenolysis, lipolysis, and gene transcription.

Guanylyl cyclase, or GC, catalyzes the conversion of guanosine triphosphate (GTP) into cyclic guanosine monophosphate (cGMP) and pyrophosphate. cGMP also acts as a second messenger, activating protein kinase G (PKG) and modulating ion channels. It is involved in processes like smooth muscle relaxation, platelet aggregation inhibition, and photoreception in the retina.

The activity of cyklázy is tightly regulated. Adenylyl cyclase can be activated or inhibited by G proteins, which are themselves regulated by receptors that bind extracellular signaling molecules. Guanylyl cyclase can be activated by nitric oxide (NO) or by natriuretic peptides. The disruption of cyklázy function is implicated in various diseases, making them important targets for drug development.