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)

l-Threonine deaminase (l-threonine dehydratase [deaminating], EC 4.2.2.16) has been shown to be involved in the regulation of three of the enzymes of isoleucine-valine biosynthesis in yeast. Mutations affecting the affinity of the enzyme for isoleucine also affected the repression of acetohydroxyacid synthase, dihydroxyacid dehydrase, and reductoisomerase. The data indicate that isoleucine must be bound for effective repression of these enzymes to take place. In a strain with a nonsense mutation midway in liv 1, the gene for threonine deaminase, starvation for isoleucine or valine did not lead to derepression of the three enzymes; starvation for leucine did. The effect of the nonsense mutation is recessive; it is tentatively concluded, therefore, that intact threonine deaminase is required for derepression by two of the effectors for multivalent repression, but not by the third. A model is presented which proposes that a regulatory species of leu tRNA(leu) is the key intermediate for repression and that threonine deaminase is a positive element, regulating the available pool of charged leu tRNA by binding it.
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PMID:Involvement of threonine deaminase in repression of the isoleucine-valine and leucine pathways in Saccharomyces cerevisiae. 457 Jul 83

The levels of the five enzymes required for isoleucine and valine synthesis were examined under several growth conditions in strain K-12 of Escherichia coli and mutants derived from it. In strains with wild type repressibility, the same pattern of derepression was found on limiting isoleucine as is found to be constitutive in strain Tir-8, which has an altered isoleucine-activating enzyme. Homoserine dehydrogenase, which is essential for the biosynthesis of threonine and is normally derepressed on limiting isoleucine or threonine, is also derepressed in strain Tir-8. Threonine deaminase and homoserine dehydrogenase were partially repressed in strain Tir-8 by very high levels of isoleucine, but were not further derepressed over levels in minimal medium by limiting isoleucine.
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PMID:Isoleucine and valine metabolism of Escherichia coli. XVI. Pattern of multivalent repression in strain K-12. 487 Feb 82

Growth of Pseudomonas cepacia 249 on D-threonine required a mutation to permit D-hydroxyamino acid deaminase formation and L-valine to overcome alpha-ketobutyrate toxicity. Strain 249 lacked a second D-hydroxyamino acid deaminase formed by other strains.
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PMID:Hydroxyamino acid utilization and alpha-ketobutyrate toxicity in Pseudomonas cepacia. 677 65

PS-5 was deacetylated to NS-5 (deacetylated PS-5) by l-amino acid acylase from porcine kidney and D-amino acid acylase from Streptomyces olivaceus but not by l-amino acid acylase from Aspergillus sp. Using PS-5, N-chloroacetyl-l-phenylalanine and N-chloroacetyl-D-valine as substrates, acylase producers were screened among facultative methanol-assimilating bacteria. Most of the microbes tested were active and could be classified into two groups of l-acylase producers and L-& D-acylase producers. Pseudomonas sp. 1158 which deacetylated the three substrates was chosen for further study. Cells of the bacterium entrapped in polyacrylamide gel and its acylase activities immobilized on DEAE-Sephadex were found to be useful for conversion of PS-5 to NS-5.
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PMID:Deacetylation of PS-5, a new beta-lactam compound, I. Microbial deacetylation of PS-5. 689 41

The crystal structure for the negative regulator (AmiC) of the amidase operon from Pseudomonas aeruginosa has been solved at a resolution of 2.1 A. AmiC is the amide sensor protein in the amidase operon and regulates the activity of the transcription antitermination factor AmiR, which in turn regulates amidase expression. The AmiC structure consists of two domains with an alternating beta-alpha-beta topology. The two domains are separated by a central cleft and the amide binding site is positioned in this cleft at the interface of the domains. The overall fold for AmiC is extremely similar to that for the leucine-isoleucine-valine binding protein (LivJ) of Escherichia coli despite only 17% sequence identity, however, the two domains of AmiC are substantially closed compared with LivJ. The closed structure of AmiC is stabilized significantly by the bound acetamide, suggesting a molecular mechanism for the process of amide induction. The amide binding site is extremely specific for acetamide and would not allow a closed conformation in the presence of the anti-inducer molecule butyramide.
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PMID:Crystal structure of AmiC: the controller of transcription antitermination in the amidase operon of Pseudomonas aeruginosa. 781 19

Escherichia coli (muT, mutD, Leu-) cells transformed with plasmid pYKD59 harbouring the pac gene encoding penicillin acylase (PA) from Kluyvera citrophila ATCC 21285 were exposed to environmental conditions that made expression of this enzyme essential for growth. Under these conditions, spontaneous mutants were isolated that used adipyl-L-leucine as the sole source of L-leucine. DNA sequencing of the mutant pac genes identified a transversion mutation of thymine to guanine at position 1163. This mutation was located in the beta-subunit of the enzyme and resulted in conversion of Phe-360 to valine. The assignment of this mutation to the shift in substrate specificity was further confirmed by site-directed mutagenesis. Secondary-structure prediction of the region surrounding Phe-360 suggests that this mutation should not produce any significant structural change. The purified mutant acylase was able to hydrolyse adipyl-, glutaryl-, valeryl-, caproyl-, heptanoyl- and phenoxyacetyl-L-leucine at pH 5 with greater efficiency than the wild-type enzyme. However, the mutant enzyme was not able to hydrolyse glutaryl-7-aminocephalosporanic acid and had lost 90% and 50% of activity on penicillin G and phenylacetyl-L-leucine respectively. Nevertheless, mutant PA retained its original activity on 6-nitro-3-phenylacetamidobenzoate and p-nitrophenylphenylacetate, suggesting that the binding specificity of PA by the acyl and amine moieties of the substrate are not independent phenomena. The small differences observed between the c.d. spectra of the mutant enzyme recorded at pH 5 and 8 suggest the existence of different conformational states at the two pH values, but these differences were indistinguishable from those observed in the native enzyme and cannot be correlated with the shift in substrate specificity. Our results demonstrate that it is possible to change the specificity of PA by laboratory evolution and use it to identify the amino acids involved in substrate recognition. However, the synchronous participation of the alpha- and beta-subunits in the complex induced-fit-like mechanism of acylases suggests that, to obtain new enzymes for industrial application, the selection pressure should be specifically designed for the compound of interest.
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PMID:Changing the substrate specificity of penicillin G acylase from Kluyvera citrophila through selective pressure. 798 Apr 57

Extracellular solute-binding proteins of bacteria serve as chemoreceptors, recognition constituents of transport systems, and initiators of signal transduction pathways. Over 50 sequenced periplasmic solute-binding proteins of gram-negative bacteria and homologous extracytoplasmic lipoproteins of gram-positive bacteria have been analyzed for sequence similarities, and their degrees of relatedness have been determined. Some of these proteins are homologous to cytoplasmic transcriptional regulatory proteins of bacteria; however, with the sole exception of the vitamin B12-binding protein of Escherichia coli, which is homologous to human glutathione peroxidase, they are not demonstrably homologous to any of the several thousand sequenced eukaryotic proteins. Most of these proteins fall into eight distinct clusters as follows. Cluster 1 solute-binding proteins are specific for malto-oligosaccharides, multiple oligosaccharides, glycerol 3-phosphate, and iron. Cluster 2 proteins are specific for galactose, ribose, arabinose, and multiple monosaccharides, and they are homologous to a number of transcriptional regulatory proteins including the lactose, galactose, and fructose repressors of E. coli. Cluster 3 proteins are specific for histidine, lysine-arginine-ornithine, glutamine, octopine, nopaline, and basic amino acids. Cluster 4 proteins are specific for leucine and leucine-isoleucine-valine, and they are homologous to the aliphatic amidase transcriptional repressor, AmiC, of Pseudomonas aeruginosa. Cluster 5 proteins are specific for dipeptides and oligopeptides as well as nickel. Cluster 6 proteins are specific for sulfate, thiosulfate, and possibly phosphate. Cluster 7 proteins are specific for dicarboxylates and tricarboxylates, but these two proteins exhibit insufficient sequence similarity to establish homology. Finally, cluster 8 proteins are specific for iron complexes and possibly vitamin B12. Members of each cluster of binding proteins exhibit greater sequence conservation in their N-terminal domains than in their C-terminal domains. Signature sequences for these eight protein families are presented. The results reveal that binding proteins specific for the same solute from different bacteria are generally more closely related to each other than are binding proteins specific for different solutes from the same organism, although exceptions exist. They also suggest that a requirement for high-affinity solute binding imposes severe structural constraints on a protein. The occurrence of two distinct classes of bacterial cytoplasmic repressor proteins which are homologous to two different clusters of periplasmic binding proteins suggests that the gene-splicing events which allowed functional conversion of these proteins with retention of domain structure have occurred repeatedly during evolutionary history.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Structural, functional, and evolutionary relationships among extracellular solute-binding receptors of bacteria. 833 70

1-Aminocyclopropane-1-carboxylate (ACC) deaminase catalyzes the cyclopropane ring fragmentation and deamination of ACC. Replacement of cysteine with alanine at a reactive thiol site, Cys-162, of ACC deaminase did not affect the enzyme activity, in spite of the previous result that modification of Cys-162 caused complete loss of the enzyme activity. Substitution of glycine or valine for the cysteine residue gave a higher Km for ACC without a significant change of the K0, indicating that changes of the amino acid side chain had structural effects on substrate binding. Replacement of lysine with alanine at the pyridoxal phosphate (PLP) binding site of the ACC deaminase caused a lower content of PLP and loss of detectable activity of ACC deamination. This mutant enzyme, K51A, showed absorption peaks at 330 nm and 405 nm. The peak at 405 nm was shifted to about 425 nm by the addition of ACC, D-, L-alanine, and D-, L-serine. The formation of aldimine complexes indicated by the spectral shift was reversible. It is suggested that lysine 51 affects the formation of holoenzyme and is important in catalysis.
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PMID:Substitutions of alanine for cysteine at a reactive thiol site and for lysine at a pyridoxal phosphate binding site of 1-aminocyclopropane-1-carboxylate deaminase. 909 53

AmiC is the negative regulator of the amidase operon which is involved in amide metabolism in the cytosol of Pseudomonas aeruginosa. Crystal structures show that AmiC contains two large domains that are very similar to the periplasmic leucine-isoleucine-valine binding protein (LivJ) of Escherichia coli. Synchrotron X-ray and neutron (in 100% 2H2O buffer) scattering data were obtained for AmiC in the presence of its substrate acetamide and its anti-inducer butyramide which binds more weakly to AmiC than acetamide. Guinier analyses to obtain radius of gyration RG and molecular weight Mr values showed that AmiC formed trimers whose formation was favored in the presence of acetamide and which exhibited concentration-dependent properties at concentrations between 0.4 and 2 mg/mL. Above 2 mg/mL, where trimers predominated, the RG data were identical within 0.05 nm for AmiC-acetamide and AmiC-butyramide with mean X-ray and neutron RG values of 3.35 and 3. 28 nm, respectively. Scattering curve fits constrained by the crystal structure of AmiC-acetamide were evaluated in order to describe a model for trimeric AmiC. A translational search of parallel alignments of three monomers to form a symmetric AmiC homotrimer gave a good X-ray curve fit. Combinations of calculated curves for monomeric, dimeric, trimeric, and tetrameric AmiC as seen in the crystal structure of AmiC gave reasonable but weaker X-ray curve fits which did not favor the existence of tetrameric AmiC. It is concluded that AmiC exhibits novel ligand-dependent oligomerization properties in solution when these are compared to other members of the periplasmic binding protein superfamily, where AmiC exists in monomeric and trimeric forms, the proportions of which depend on the presence of acetamide or butyramide.
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PMID:Oligomerization of the amide sensor protein AmiC by x-ray and neutron scattering and molecular modeling. 920 49

A thrombin-like enzyme, balterobin, was purified from the venom of Bothrops alternatus. The purification steps included Sephadex G-75, heparin-sepharose and reverse phase HPLC C-18 column. Balterobin showed an apparent molecular weight of 30,000 in non-reduced conditions and displays a specific coagulant activity of 32.8 NIH units/mg over bovine fibrinogen. It also exhibits arginine amidase activity on DL-BAPNA. Like thrombin-like enzymes from other snakes, balterobin possesses valine as N-terminal residue, and is inhibited by PMSF.
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PMID:Purification and partial characterization of a thrombin-like enzyme, balterobin, from the venom of Bothrops alternatus. 969 Jul 98


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