Cyclase

About: Cyclase is a research topic. Over the lifetime, 10162 publications have been published within this topic receiving 388566 citations.

Mode of action of endogenous opiate peptides.

Abstract: AS THE culmination of a search for endogenous ligands of the opiate receptor1–4, the structures of two closely related pentapeptides, isolated from porcine (brain, with morphine-like properties in pharmacological tests, have been reported by Hughes et al.5 The amino acid sequences of the pentapeptides, termed methionine enkephalin and leucine enkephalin, are Tyr-Gly-Gly-Phe-Met (Met5-enkephalin) and Tyr-Gly-Gly-Phe-Leu (Leu5-enkephalin), respectively. They behave as highly potent opiates in the mouse vas deferens and guinea pig ileum assays5. In addition, animals tolerant to morphine are also tolerant to enkephalin6. The action of the pentapeptides in the guinea pig ileum5 and when injected intracerebrally or intracerebroventricularly7–9 is very short lived, perhaps because of proteolytic degradation. A related peptide, with longer chain length has been shown to have a long duration of action10. Morphine and other narcotics have been shown to bind to the opiate receptor11–13 and inhibit adenylate cyclase activity in homogenates of neuroblastoma × glioma hybrid cells14,15, to inhibit cyclic AMP accumulation in intact hybrid cells15,16 and in rat brain homogenates17. We have tested the effects of Met5- and Leu5-enkephalin on NG108-15 adenylate cyclase activity, and show here that endogenous opiate peptides are potent, receptor-mediated, inhibitors of adenylate cyclase of neuroblastoma × glioma hybrid cells.

Beyond receptors: multiple second-messenger systems in brain.

Abstract: Second-messenger systems play a major role in mediating neurotransmitter actions. In recent years our understanding of the organization and function of two prominent second-messenger systems has progressed rapidly--the adenylate cyclase and phosphoinositide systems. Guanosine triphosphate-binding proteins, which are especially abundant in brain, couple transmitter receptors to the key second-messenger generating enzymes in both of these systems. Whereas activation of adenylate cyclase produces a single intracellular messenger, cyclic AMP, stimulation of the phosphoinositide system generates at least two, inositol trisphosphate and diacylglycerol. Inositol trisphosphate mobilizes calcium from intracellular stores, and diacylglycerol, like cyclic adenosine monophosphate, activates a phosphorylating enzyme, protein kinase C. These second-messenger systems are particularly enriched in the brain where they modulate many aspects of synaptic transmission.

Coupling of hormone receptors to adenylate cyclase of different cells by cell fusion

Abstract: A new hormone responsiveness can be conferred on an adenylate cyclase system by coupling it to a foreign hormone receptor. Receptor and enzyme from cells of different species can be compatible with each other.