Glycohydrolase

Influenza virus sialidase (Fig. 2) is a tetrameric glycoprotein consisting of four identical subnnits (Colman and Ward 1985), and acts as a glycohydrolase that removes a-ketosidically linked terminal AT-acetylneuraminic acid residues from gly-coconjugates. 

BRCT BRCAl C-terminus-like DBD DNA-binding domain dPARP Drosophila PARP MPTP l-methyl-4-phenyl-l,2,3,6-tetrahydropyridine NAD+ Nicotinamide adenine dinucleotide NAm Nicotinamide NLS Nuclear locahzation signal OAADPR O-acetyl-ADP-ribose PAR Poly(ADP-ribose) PARG Poly(ADP-ribose) glycohydrolase PARP Poly(ADP-ribose) polymerase PARylation poly(ADP-ribosyl)ation... 

Bonicalzi ME, Vodenicharov M, Coulombe M, Gagne JP, Poirier GG (2003) Alteration of poly(ADP-ribose) glycohydrolase nucleocytoplasmic shuttling characteristics upon cleavage by apoptotic proteases. Biol Cell 95 635-644... 

The enzyme catalyzing the addition of ADP-ribose units onto the histones and itself is poly(ADP-ribose) polymerase or synthetase. Poly(ADP-ribose) polymerase is a nuclear, DNA-dependent enzyme that is stimulated by DNA breaks [302]. This property of the enzyme would target its action to sites that have DNA strand breaks (regions of the genome involved in replication, repair, recombination). The enzyme is associated with chromatin areas and perichromatin regions in interphase Chinese hamster ovary cells [312]. Degradation of the ADP-ribose polymer is catalyzed by the nuclear enzyme poly(ADP-ribose) glycohydrolase and ADP-ribosyl protein lyase. 

Realini and Althaus [313] have put forth the hypothesis that poly(ADP-ribosylation) may have a function in histone shuttling. They propose that poly(ADP-ribose) polymerase directed to sites of DNA strand breaks would auto-modify itself generating multiple ADP-ribose polymers. The polymers would lead to the dissociation of the histones from DNA onto the polymers. The DNA would now be free for processing (e.g., by enzymes involved in excision repair). The action of poly(ADP-ribose) glycohydrolase would degrade the... 

Figure 1. Amino acid sequences of microbial glycohydrolases. A Aureobasid-iwn sp. endo-xylanase Sc Schizophyllwn commune endo-xylanase C Chainia sp. endo-xylanase Bp Bacillus pumilus endo-xylanase Bs Bacillus subtilis Bacillus circulans endo-xylanase Pf Pseudomonas fluorescens endo-xylanase B alkalophilic Bacillus sp. endo-xylanase Ct Clostridium thermocellum endo-xylanase Cf Cellulomonas fimi cellobiohydrolase Ca Cryptococcus albidus endo-xylanase. Residue numbers are those of the adjacent residue, counting from the N-terminus of the mature protein.

Figure 2. Comparison of homologies between microbial glycohydrolases. Percentages arc based on the number of paired amino acid residues between any two enzymes. Symbols are as in Figure 1.

NAD glycohydrolases from rat liver nuclei, 66, 151 poly(ADP-ribose) synthetase from rat liver nuclei, 66, 154 poly(ADP-ribose) synthetase from calf thymus, 66, 159 extraction and quantitative determination of larger than tetrameric endogenous polyadenosine diphosphoribose from animal tissues, 66, 165 covalent modification of proteins by metabolites of NAD, 66, 168 coenzyme activity of NAD bound to polymer supports through the adenine moiety, 66, 176 use of differently immobilized nucleotides for binding NAD -dependent dehydrogenases, 66, 192. 

NAD GLYCOHYDROLASE Hydrolysis of nucleoside diphosphate, NUCLEOSIDE DIPHOSPHATASE Hydrolysis of 3 -ribonucleotide,... 

NAD GLYCOHYDROLASE NAD -dependent dehydrogenases, ABSORPTION SPECTROSCOPY NAD -dependent enzymes,... 

Controls with the anti-glycohydrolases IgG, first incubated with the enzymic extract before being applied in thin sections, showed no labeling (Fig. 2B). Other controls performed, i.e., replacement of the primary antibody by normal rabbit serum or preimmune serum, suppression of the first step corresponding to the primary antibody, or labeling of uninfected wood specimen, were also negative. 

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