Cyclase

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

Autoantibodies against CD38 (ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase) that impair glucose-induced insulin secretion in noninsulin- dependent diabetes patients.

Abstract: Cyclic ADP-ribose (cADPR) has been shown to be a mediator for intracellular Ca2+ mobilization for insulin secretion by glucose in pancreatic beta cells, and CD38 shows both ADP-ribosyl cyclase to synthesize cADPR from NAD+ and cADPR hydrolase to hydrolyze cADPR to ADP-ribose. We show here that 13.8% of Japanese non-insulin-dependent diabetes (NIDDM) patients examined have autoantibodies against CD38 and that the sera containing anti-CD38 autoantibodies inhibit the ADP-ribosyl cyclase activity of CD38 (P

Mechanism of galanin-inhibited insulin release

Abstract: In the insulin-secreting beta cell line Rin m 5F, galanin, a newly discovered ubiquitous neuropeptide, inhibited, by 50%, the stimulation of insulin release induced by gastric inhibitory polypeptide (GIP) or forskolin, i.e. two cAMP-generating effectors. In contrast, it failed to decrease the stimulation of insulin release elicited by either the Ca2+-mobilizing agent, carbamoylcholine, or by dibutyryl-cAMP. Concomitantly, galanin inhibited the GIP-and forskolin-stimulated cAMP production. Furthermore, adenylate cyclase in membranes from Rin m 5F cells was highly sensitive to galanin, which exerted a marked inhibitory effect on the forskolin-stimulated enzyme activity. All these galanin effects were observed at low physiological doses, in the nanomolar range. Overnight treatment of the Rin m 5F cells with pertussis toxin completely abolished the inhibitory effect of galanin on insulin release, cAMP production and adenylate cyclase activity. Moreover, pertussis toxin specifically ADP-ribosylated a 39-kDa protein present in membranes from those cells. Taken together, these data show that the galanin inhibition of insulin release most likely occurs through the inhibition of adenylate cyclase, involving a petussis-toxin-sensitive inhibitory GTP-binding regulatory protein.

Use of calmodulin affinity chromatography for purification of specific calmodulin-dependent enzymes.

Abstract: Publisher Summary This chapter discusses the preparation of the calmodulin (CaM)-affinity column and its general application for the purification of CaM-regulated proteins. Owing to the large number of CaM-regulated proteins contained in most tissue sources, CaM-Sepharose 4B affinity column chromatography is not sufficient by itself for the purification of a specific enzyme to homogeneity. However, in combination with additional protein purification techniques, several homogeneous CaM-dependent enzymes and proteins are obtained. The purification of bovine brain CaM-dependent cyclic nucleotide phosphodiesterase and calcineurin is presented as an example in the chapter. Two procedures have been used in the preparation of CaM-Sepharose 4B: one uses the cyanogen bromide-activated gel and the other uses a divinyl sulfone activation method. Because CaM is multifunctional, many enzymes and proteins are capable of interacting with the CaM-Sepharose 4B column. Therefore, CaM-affinity chromatography is not sufficient by itself to purify one enzyme to homogeneity. However, several CaM-regulated proteins have been purified using CaM-Sepharose 4B affinity chromatography in combination with other purification steps. These include CaM-dependent phosphodiesterase, calcineurin, myosin light-chain kinase, phosphorylase kinase, erythrocyte Ca 2+ , Mg 2+ -ATPase, calmodulin-binding protein II, plant NAD kinase, and adenylate cyclase.

VIP-mediated G protein-coupled Ca2+ influx activates a constitutive NOS in dispersed gastric muscle cells.

Abstract: Vasoactive intestinal peptide (VIP) and peptide histidine-isoleucine (PHI) receptors and the signaling pathways to which they are coupled were characterized in dispersed gastric smooth muscle cells. Radioligand binding using 125I-labeled VIP and PHI identified 4 classes of receptors: VIP-preferring and PHI-preferring receptors recognized by both ligands and readily desensitized by the preferred ligand, and VIP-specific and PHI-specific receptors recognized by only 1 ligand and resistant to desensitization. All except VIP-specific receptors were coupled to adenylate cyclase. VIP-specific receptors mediated a G protein-coupled Ca2+ influx that led to activation of NO synthase (NOS), NO-dependent activation of soluble guanylate cyclase, and activation of guanosine 3',5'-cyclic monophosphate (cGMP) kinase resulting in muscle relaxation. The entire cascade was blocked by Ca2+ channel and/or calmodulin antagonists. The NOS inhibitor NG-nitro-L-arginine abolished L-[3H]citrulline (coproduct of NO synthesis) and cGMP generation and partly inhibited (52 +/- 4%) relaxation. The components of response mediated by VIP-specific receptors (increase in [Ca2+]i, L-[3H]citrulline, and cGMP) were preserved after desensitization. Insertion of guanosine 5'-O-(beta-thio)diphosphate into reversibly permeabilized muscle cells abolished responses mediated by VIP-preferring and VIP-specific receptors. VIP stimulated both adenosine 3',5'-cyclic monophosphate (cAMP)-kinase and cGMP-kinase activities consistent with stimulation of cAMP and cGMP. Both kinases contributed to relaxation that was partly inhibited by cAMP-kinase [H-89 and (R)-p-adenosine 3',5'-cyclic monophosphorothioate] and cGMP-kinase (KT-5823) inhibitors and abolished by a combination of the 2 types of inhibitors. We conclude that VIP-specific receptors mediate a G protein-coupled Ca2+ influx leading to activation of a constitutive Ca2+/calmodulin-dependent NOS and generation of NO, which is partly responsible for relaxation in smooth muscle.