Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.5.1.4 (deaminase)
5,113 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A conserved amino acid sequence motif was identified in four distinct groups of enzymes that catalyze the hydrolysis of the alpha-beta phosphate bond of ATP, namely GMP synthetases, argininosuccinate synthetases, asparagine synthetases, and ATP sulfurylases. The motif is also present in Rhodobacter capsulata AdgA, Escherichia coli NtrL, and Bacillus subtilis OutB, for which no enzymatic activities are currently known. The observed pattern of amino acid residue conservation and predicted secondary structures suggest that this motif may be a modified version of the P-loop of nucleotide binding domains, and that it is likely to be involved in phosphate binding. We call it PP-motif, since it appears to be a part of a previously uncharacterized ATP pyrophophatase domain. ATP sulfurylases, NtrL, and OutB consist of this domain alone. In other proteins, the pyrophosphatase domain is associated with amidotransferase domains (type I or type II), a putative citrulline-aspartate ligase domain or a nitrilase/amidase domain. Unexpectedly, statistically significant overall sequence similarity was found between ATP sulfurylase and 3'-phosphoadenosine 5'-phosphosulfate (PAPS) reductase, another protein of the sulfate activation pathway. The PP-motif is strongly modified in PAPS reductases, but they share with ATP sulfurylases another conserved motif which might be involved in sulfate binding. We propose that PAPS reductases may have evolved from ATP sulfurylases; the evolution of the new enzymatic function appears to be accompanied by a switch of the strongest functional constraint from the PP-motif to the putative sulfate-binding motif.
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PMID:A P-loop-like motif in a widespread ATP pyrophosphatase domain: implications for the evolution of sequence motifs and enzyme activity. 773 53

The N-end rule relates the in vivo half-life of a protein to the identity of its N-terminal residue. Tertiary destabilizing N-terminal residues asparagine and glutamine function through their conversion, by enzymatic deamidation, into the secondary destabilizing residues aspartate and glutamate, whose activity requires their enzymatic conjugation to arginine, one of the primary destabilizing residues. We isolated a Saccharomyces cerevisiae gene, termed NTA1, that encodes an amidase (Nt-amidase) specific for N-terminal asparagine and glutamine. Alterations at the putative active-site cysteine of the 52-kDa Nt-amidase inactivate the enzyme. Null nta1 mutants are viable but unable to degrade N-end rule substrates that bear N-terminal asparagine or glutamine. The effects of overexpressing Nt-amidase and other components of the N-end rule pathway suggest interactions between these components and the existence of a multienzyme targeting complex.
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PMID:Yeast N-terminal amidase. A new enzyme and component of the N-end rule pathway. 774 55

The peptide-N4-(N-acetylglucosaminyl) asparagine amidase (PNGase Se) earlier described [Lhernould S., Karamanos Y., Bourgerie S., Strecker G., Julien R., Morvan H. (1992) Glycoconjugate J 9:191-97] was partially purified from cultured Silene alba cells using affinity chromatography. The enzyme is active between pH 3.0 and 6.5, and is stable in the presence of moderate concentrations of several other protein unfolding chemicals, but is readily inactivated by SDS. Although the enzyme cleaves the carbohydrate from a variety of animal and plant glycopeptides, it does not hydrolyse the carbohydrate from most of the corresponding unfolded glycoproteins in otherwise comparable conditions. The substrate specificity of this plant PNGase supports the hypothesis that this enzyme could be at the origin of the production of 'unconjugated N-glycans' in a suspension medium of cultured Silene alba cells.
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PMID:Characterization of the peptide-N4-(N-acetylglucosaminyl) asparagine amidase (PNGase Se) from Silene alba cells. 779 18

Co- and post-translational amino-terminal processing of proteins is one mechanism by which intracellular proteins can be either protected from or targeted to degradation by the N-end Rule pathway (Bachmair, A., Finley, D., and Varshavsky, A. (1986) Science 234, 179-186). A novel enzyme, protein NH2-terminal asparagine amidohydrolase, which can function in this pathway by potentially directing critical regulatory proteins possessing an amino-terminal asparagine residue formed from the removal of N-acetylmethionine, has recently been purified and characterized (Stewart, A.E., Arfin, S. M., and Bradshaw, R. A. (1994) J. Biol. Chem. 269, 23509-23517). Here, we report the isolation and characterization of a cDNA for porcine protein NH2-terminal asparagine amidohydrolase, which indicates that it is a new type of enzyme, not homologous to any previously identified protein. This provides strong evidence for the importance of regulated protein degradation in cellular functioning.
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PMID:The sequence of porcine protein NH2-terminal asparagine amidohydrolase. A new component of the N-end Rule pathway. 781 82

The glycosylation pattern of the external envelope glycoprotein of human immunodeficiency virus type 2 (HIV-2) was studied in dependence on host cells and virus isolates. Strains HIV-2ALT, HIV-2ROD and HIV-2D194, differing in their biological properties and in the amino acid sequences of their env genes, were propagated in MOLT4, HUT78 and U937 cells, in human peripheral blood lymphocytes and monocytes/macrophages in the presence of [6-3H]glucosamine. Radiolabelled viral glycoproteins were isolated from the cell-free supernatants and digested with trypsin. Glycans were sequentially liberated by endo-beta-N-acetylglucosaminidase H and peptide-N4-(N-acetyl-beta-glucosaminyl) asparagine amidase F, and fractionated according to charge and size. Comparison of the oligosaccharide profiles revealed that the envelope glycoproteins of different virus isolates, propagated in the same host cells, yielded very similar glycan patterns, whereas cultivation of an isolate in different host cells resulted in markedly divergent oligosaccharide maps. Variations concerned the proportion of high-mannose-, hybrid- and complex-type substituents, as well as the state of charge and structural parameters of the complex-type species. As a characteristic feature, complex-type glycans of macrophage-derived viral glycoprotein were almost exclusively substituted by lactosamine repeats. Hence, glycosylation of the HIV-2 external envelope glycoprotein seems to be primarily governed by host cell-specific factors rather than by the amino acid sequence of the corresponding polypeptide backbone.
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PMID:Oligosaccharide profiles of HIV-2 external envelope glycoprotein: dependence on host cells and virus isolates. 782 9

Peptide-N4-(N-acetyl-beta-D-glucosaminyl)asparagine amidase F (PNGase F) is an amidase that cleaves the beta-aspartylglucosylamine bond of asparagine-linked glycans. The 34.8-kDa (314 amino acids) enzyme has a very broad substrate specificity and is extensively used for studies of the structure and function of glycoproteins. Enzymatic activity of PNGase F requires recognition of both the peptide and the carbohydrate components of the substrate. Only limited information regarding the mechanism of action of the enzyme is available. The three-dimensional structure of PNGase F has been determined by X-ray crystallography at 2.2-A resolution. The protein folds into two domains comprising residues 1-137 and 143-314, respectively. Both domains have eight-stranded antiparallel beta-sandwich motifs that are very similar in geometry. Both sandwiches have parallel principal axes and lie side by side. The covalent link between the domains is located at the top end of the molecule. Extensive hydrogen-bonding contacts occur along the full length of the interface between the two domains. Three different areas, all at the interface between the two domains, have been identified as possible locations for the active site of the enzyme. These include a hydrophobic bowl of about 20 A in diameter on one surface of the molecule, a long polar cleft on the opposite side, and a cleft at the bottom, which is lined with large aromatic residues including eight tryptophans.
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PMID:Crystal structure of peptide-N4-(N-acetyl-beta-D-glucosaminyl)asparagine amidase F at 2.2-A resolution. 791 86

In the present study, we investigated the nature and the importance of glycosylation of two mammalian bombesin receptors, the neuromedin B receptor (NMB-R) and the gastrin-releasing peptide receptor (GRP-R), using chemical cross-linking and enzymatic deglycosylation. [125I]-(D-Tyr0)NMB cross-linked to native NMB-R on rat C-6 glioblastoma cells or rat NMB-R transfected into BALB 3T3 cells revealed a single broad band, M(r) = 63,000, on both cell types that was not altered by DTT. NMB inhibited cross-linking specifically and saturably with an IC50 of 4.8 and 6.1 nM for C-6 and NMB-R transfected cells, respectively, and there was a close correlation between its ability to inhibit binding and its ability to inhibit cross-linking. A single broad band of M(r) = 82,000 was cross-linked with [125I]GRP on mouse GRP-R transfected BALB 3T3 cells. Peptide-N4-(N-acetyl-beta- glucosaminyl)asparagine amidase F (PNGase F) digestion increased the mobility of the original band in C-6, NMB-R, and GRP-R transfected cell membranes. Endoglycosidase H (Endo-H) and endoglycosidase F2 (Endo-F2) digestion had no effect on both transfected cells. Neuraminidase digestion slightly increased the mobility of the original band in NMB-R transfected cell membranes; however, it had no effect on GRP-R transfected cell membranes. Endo-alpha-N-acetylglucosaminidase (O-glycanase) digestion subsequent to neuraminidase treatment showed no additional effect on either receptor. Serial partial deglycosylation of cross-linked NMB-Rs with PNGase F treatment for different incubation periods revealed one band of partially glycosylated receptor (53 kDa) besides the fully glycosylated and fully deglycosylated ones, showing that NMB-R has two oligosaccharide chains. Similarly, three partially deglycosylated species (72, 62, and 52 kDa) are seen with the GRP-R, indicating that the GRP-R has four oligosaccharide chains. Treatment of unlabeled membranes with PNGase F followed by affinity labeling resulted in fully deglycosylated NMB-R or 75% deglycosylated GRP-R. Deglycosylation of the NMB-R did not alter its affinity for NMB or alter G-protein coupling; however, 75% deglycosylation of the GRP-R both decreased its affinity for GRP and altered its ability to couple to G-proteins. The present results demonstrate that NMB-R on native and transfected cells is an N-linked sialoglycoprotein with two triantenary and/or tetraantenary complex oligosaccharide chains. The apparent M(r) of this sialoglycoprotein is 63,000, and this protein does not contain disulfide-linked subunits or O-linked carbohydrates.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Glycosylation of bombesin receptors: characterization, effect on binding, and G-protein coupling. 794 1

We previously reported the occurrence of oligomannosides and xylomannosides corresponding to unconjugated N-glycans (UNGs) in the medium of a white campion (Silene alba) cell suspension. Attention has been focused on these oligosaccharides since it was shown that they confer biological activities in plants. In an attempt to elucidate the origin of these oligosaccharides, we studied two endoglycosidase activities, putative enzymes involved in their formation. The previously described peptide-N4-(N-acetyl-glucosaminyl) asparagine amidase activity and the endo-N-acetyl-beta-D-glucosaminidase activity described in this paper were both quantified in white campion cells during the culture cycle with variable initial concentrations of sucrose. The lower the sucrose supply, the higher the two activities. Furthermore, endoglycosidase activities were greatly enhanced after the disappearance of sugar from the medium. The production of UNGs in the culture medium rose correlatively. These data strongly suggest that the production of UNGs in our white campion cell-suspension system is due to the increase of these endoglycosidase activities, which reach their highest levels of activity during conditions of carbon starvation.
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PMID:Carbon starvation increases endoglycosidase activities and production of "unconjugated N-glycans" in Silene alba cell-suspension cultures. 799 89

PNGase F is an amidase that hydrolyzes the beta-aspartylglucosylamine bond of asparagine-linked glycopeptides and glycoproteins. Enzymatic activity of PNGase F requires the recognition of both the peptide and the carbohydrate moiety. Crystals of PNGase F were grown by sitting drop vapor diffusion methods at 10 degrees C. The precipitating buffer contains both polyethylene glycol 3350 and (NH4)2SO4 in sodium acetate buffer at pH 4.3. The crystals belong to the orthorhombic space group C222(1) with cell dimensions: a = 87.16 A, b = 125.10 A, c = 79.33 A and diffract to 1.8 A resolution.
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PMID:Crystallization and preliminary crystallographic analysis of peptide-N4-(N-acetyl-beta-D-glucosaminyl)asparagine amidase PNGase F. 805 83

The amino acid sequence and a 2-A-resolution crystallographic structure of Pseudomonas 7A glutaminase-asparaginase (PGA) have been determined. PGA, which belongs to the family of tetrameric bacterial amidohydrolases, deamidates glutamine and asparagine. The amino acid sequence of PGA has a high degree of similarity to the sequences of other members of the family. PGA has the same fold as other bacterial amidohydrolases, with the exception of the position of a 20-residue loop that forms part of the active site. In the PGA structure presented here, the active site loop is observed clearly in only one monomer, in an open position, with a conformation different from that observed for other amidohydrolases. In the other three monomers the loop is disordered and cannot be traced. This phenomenon is probably a direct consequence of a very low occupancy of product(s) of the enzymatic reaction bound in the active sites of PGA in these crystals. The active sites are composed of a rigid part and the flexible loop. The rigid part consists of the residues directly involved in the catalytic reaction as well as residues that assist in orienting the substrate. Two residues that are important for activity residue on the flexible loop. We suggest that the flexible loops actively participate in the transport of substrate and product molecules through the amidohydrolase active sites and participate in orienting the substrate molecules properly in relation to the catalytic residues.
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PMID:Structural characterization of Pseudomonas 7A glutaminase-asparaginase. 806 64


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