, are located in a region similar to that required for activity in ARH1 but different from the location of the critical vicinal glutamates in the PARG catalytic site. All findings are consistent with the conclusion that ARH3 has PARG activity but is structurally unrelated to PARG.

The silent information regulator 2 (Sir2) family of NAD-dependent N-acetyl-protein deacetylases participates in the regulation of gene silencing, chromatin structure, and longevity. In the Sir2-catalyzed reaction, the acetyl moiety of N-acetyl-histone is transferred to the ADP-ribose of NAD, yielding O-acetyl-ADP-ribose and nicotinamide. We hypothesized that, if O-acetyl-ADP-ribose were an important signaling molecule, a specific hydrolase would cleave the (O-acetyl)-(ADP-ribose) linkage. We report here that the poly-(ADP-ribose) glycohydrolase ARH3 hydrolyzed O-acetyl-ADPribose to produce ADP-ribose in a time-and Mg 2؉ -dependent reaction and thus could participate in two signaling pathways. This O-acetyl-ADP-ribose hydrolase belongs to a family of three structurally related 39-kDa ADP-ribose-binding proteins (ARH1-ARH3). ARH1 was reported to hydrolyze ADP-ribosylarginine, whereas ARH3 degraded poly(ADP-ribose). ARH3-catalyzed generation of ADP-ribose from O-acetyl-ADP-ribose was significantly faster than from poly(ADP-ribose). Like the degradation of poly(ADP-ribose) by ARH3, hydrolysis of O-acetyl-ADP-ribose was abolished by replacement of the vicinal aspartates at positions 77 and 78 of ARH3 with asparagine. The rate of O-acetyl-ADP-ribose hydrolysis by recombinant ARH3 was 250-fold that observed with ARH1; ARH2 and poly(ADP-ribose) glycohydrolase were inactive. All data support the conclusion that the Sir2 reaction product O-acetyl-ADP-ribose is degraded by ARH3.ADP-ribosylhydrolase ͉ ADP-ribosyltransferase ͉ sirtuin ͉ ADP-ribose S ilent information regulator 2 (Sir2) family proteins are involved in gene silencing, chromosomal stability, and lifespan extension (1, 2). In the presence of NAD, Sir2 couples protein deacetylation with formation of O-acetyl-ADP-ribose and release of nicotinamide (3-5). NAD-dependent histone deacetylation appears to be crucial for the biological effects of Sir2. The second product of the reaction, O-acetyl-ADP-ribose, may be involved in the stabilization of chromatin and formation of Sir complexes (6, 7), although its contribution to the biological effects of Sir2 is unclear.In many biological systems, specific enzymes are responsible for the degradation of small molecules that are generated in signaling cascades, thus terminating their action. Examples include the adenylyl cyclase and guanylyl cyclase pathways, where cyclic nucleotide phosphodiesterases degrade cAMP and cGMP, respectively, thus extinguishing the signal (8). Thus far, enzymatic destruction of O-acetyl-ADP-ribose has been shown only with the Nudix family of ADP-ribose pyrophosphatases (9) (nucleoside diphosphate linked to another moiety, hence the acronym Nudix) (10) and perhaps other less selective pyrophosphatases.The extent of ADP-ribosylation of proteins is determined by the rate of opposing actions of ADP-ribosyltransferases, which catalyze the posttranslational modification, and ADP-riboseprotein hydrolases, which cleave the ADP-ribose-protein linkage, releasing ADP-ribose and regenerating unmodified protein...

No abstract

No abstract

No abstract

Coronavirus disease pandemic has led to a shortage of disinfectant alcohol (DA; 76.9-81.4% ethanol solution) in Japan. This study investigated the availability of hypochlorous acid (HA) as an alternative disinfectant to DA in clinical environment. HA is a safe and economical disinfectant with a broad antibacterial spectrum and low risk of hand irritation, which is used worldwide. In this study, HA and sodium hypochlorite solution (SH) were degraded over time and the degradation was accelerated by temperature and lighting. Results of bactericidal effects of HA revealed that the realistic effective concentration should be 200 ppm. Compared with DA, the dental carbon steel burs were more severely rusted by SH and HA. These results indicated that high concentration of HA generated on-site could be an effective and safe disinfectant for use immediately after generation with consideration of object materials in clinical environment, as an alternative to DA.

The distribution of the molluscan cardioexcitatory tetrapeptide FMRFamide (Phe-Met-Arg-Phe-NH2) in the brain of the cloudy dogfish, Scyliorhinus torazame, was examined by immunocytochemistry. FMRFamide-like immunoreactivity was demonstrated to occur extensively in various regions of the dogfish brain, except for the corpus cerebelli. Immunoreactive neuronal perikarya were located in the ganglion of the nervus terminalis, the preoptic area, and the hypothalamic periventricular gray matter consisting of the nucleus medius hypothalamicus, the nucleus lateralis tuberis, and the nucleus lobi lateralis. Some of the immunoreactive cells in the hypothalamus were identified as cerebrospinal fluid-contacting neurons. The bulk of the immunostained fibers in the nervus terminalis penetrated into the midventral portion of the telencephalon and ran dorsocaudally toward the basal telencephalon and hypothalamus, showing radial projections or ramifications. The labeled fibers were abundant in the midbasal part of the telencephalon and in the hypothalamus, where some fibers were found in loose networks around the cell bodies of the nucleus septi and hypothalamic periventricular nuclei. The fibers demonstrated in the hypothalamus terminated around the vascular wall of the primary capillary plexus of the median eminence or penetrated deeply into the pars intermedia of the hypophysis. These results suggest that, in the dogfish, an FMRFamide-like substance participates in the regulation of adenohypophysial function. This molecule may have a role as a neurotransmitter and/or neuromodulator in the central nervous system.

Enameloid is a well-mineralized tissue covering the tooth surface in fish and it corresponds to the outer-most layer of dentin. It was reported that both dental epithelial cells and odontoblasts are involved in the formation of enameloid. Nevertheless, the localization and timing of secretion of ectodermal enamel matrix proteins (EMPs) in enameloid are unclear. In the present study, the enameloid matrix during the stages of enameloid formation in spotted gar, Lepisosteus oculatus, an actinopterygian, was examined mainly by transmission electron microscopy-based immunohistochemistry using an anti-mammalian amelogenin (AMEL) antibody and antiserum. Positive immunoreactivity with the antibody and antiserum was found in enameloid from the surface to the dentin-enameloid junction just before the formation of crystallites. This immunoreactivity disappeared rapidly before the full appearance of crystallites in the enameloid during the stage of mineralization. Immunolabelling was usually found along the collagen fibrils but was not seen on the electron-dense fibrous structures, which were probably derived from matrix vesicles in the previous stage. In inner dental epithelial (IDE) cells, the granules in the distal cytoplasm often showed positive immunoreactivity, suggesting that the EMP-like proteins originated from IDE cells. EMP-like proteins in the enameloid matrix might be common to the EMP-like proteins previously reported in the collar enamel of teeth and ganoine of ganoid scales, because they exhibited marked immunoreactivity with the same anti-mammalian AMEL antibodies. It is likely that EMP-like proteins are involved in the formation of crystallites along collagen fibrils in enameloid.