Biochemical and immunological comparison of aliphatic amidases produced by Pseudomonas species

Structure of Amidase from Pseudomonas aeruginosa Showing a Trapped Acyl Transfer Reaction Intermediate State

Microbial amidases belong to the thiol nitrilases family and have potential biotechnological applications in chemical and pharmaceutical industries as well as in bioremediation. The amidase from Pseudomonas aeruginosa isa6 x 38-kDa enzyme that catalyzes the hydrolysis of a small range of short aliphatic amides. The hereby reported high resolution crystallographic structure shows that each amidase monomer is formed by a globular four-layer alphabetabetaalpha sandwich domain with an additional 81-residue long C-terminal segment. This wraps arm-in-arm with a homologous C-terminal chain of another monomer, producing a strongly packed dimer. In the crystal, the biological active homo-hexameric amidase is built grouping three such dimers around a crystallographic 3-fold axis. The structure also elucidates the structural basis for the enzyme activity, with the nitrilases catalytic triad at the bottom of a 13-A deep, funnel-shaped pocket, accessible from the solvent through a narrow neck with 3-A diameter. An acyl transfer intermediate, resulting from the purification protocol, was found bound to the amidase nucleophilic agent, Cys(166). These results suggest that some pocket defining residues should undergo conformational shifts to allow substrates and products to access and leave the catalytic pocket, for turnover to occur.

Lipase and esterase-catalyzed acylation of hetero-substituted nitrogen nucleophiles in water and organic solvents

The lipase- and esterase-catalyzed acylations of hydroxylamine and hydrazine derivatives with octanoic acid and ethyl octanoate are described. The influence of solvent and nucleophile on the initial reaction rate was investigated for a number of free and immobilized enzymes. Initial rates were highest in water, but the overall productivity was optimal in dioxane. Octanoic acid (250 g/L) was converted for 93% into the hydroxamic acid in 36 h with only 1% (w/w) Candida antarctica lipase B (Novozym 435) in dioxane at 40 degrees C. This translates to a catalyst productivity of 68.5 g. g(-1). day(-1) and a space time yield of 149 g. L(-1). day(-1), unprecedented figures in the direct reaction of an acid with a nitrogen nucleophile in an organic solvent.

Hydrazide synthesis: novel substrate specificity of amidase

The amidase from Rhodococcus rhodochrous J1, which hydrolyses amide to acid and ammonia, was found to catalyze the synthesis of hydrazide using hydrazine as a substrate. This is the first report on the hydrazide synthesis through enzymatic reactions. The enzyme also acted on benzoic acid in the presence of hydrazine, yielding benzoic hydrazide. Together with the finding that benzoic hydrazide was converted into benzoic acid (when it was used as a substrate in the absence of hydrazine), these unique characteristics suggest that the reaction route for the formation of the acid from the hydrazide and that of the hydrazide from the acid are reversible to each other via the acyl-enzyme. Not only aromatic hydrazides but also aliphatic hydrazides were synthesized from the corresponding amides and hydrazine.

Cloning and primary structure of the wide-spectrum amidase from Brevibacterium sp. R312: high homology to the amiE product from Pseudomonas aeruginosa

A Brevibacterium sp. R312 DNA fragment encoding the wide-spectrum amidase (EC 3.5.1.4) has been cloned and sequenced, using limited amino acid (aa) sequence information obtained from the purified enzyme. The deduced aa sequence showed more than 80% strict identity with the Pseudomonas aeruginosa aliphatic amidase, the product of the amiE gene, suggesting a horizontal transfer of the gene during evolution between Gram+ and Gram- bacteria.

An experiment in enzyme evolution. Studies with Pseudomonas aeruginosa amidase

The regulation of amidase synthesis in P. aeruginosa is under positive control. This review describes the experimental evolution of amidase and its regulator protein for the hydrolysis of novel substrates and experiments to elucidate the mechanism of the control system.

Immunological relatedness of histidine ammonia-lyases from some species of Pseudomonas: taxonomic implication

1. Histidine ammonia-lyases (histidase EC 4.3.1.3) from Pseudomonas testosteroni NCIB 10808 and Pseudomonas putida NCIB 10807 were purified and specific antibody was raised to each separately in a rabbit. 2. Immunological cross-reactions of each antibody to histidine ammonia-lyases from various species of Pseudomonas were examined by the enzyme inhibition test. 3. The immunological data obtained suggest that these Pseudomonas species can be classified into three groups. These cross-reactions tend to indicate a certain degree of homology within species in a group but not between groups.

Purification and properties of 2-hydroxy-6-oxo-2,4-heptadienoate hydrolase from two strains of Pseudomonas putida

Growth on phenol of two strains of Pseudomonas putida biotype A, NCIB 10015 and NCIB 9865, elicits the synthesis of an enzyme that hydrolyzes 2-hydroxy-6-oxo-2,4-heptadienoate to 2-oxopent-4-enoate. The purified enzyme from Pseudomonas NCIB 10015 has a molecular weight of 118,000 and dissociates in sodium dodecyl sulfate to a species of molecular weight 27,700; the enzyme from Pseudomonas NCIB 9865 has a molecular weight of 100,000 and dissociates to a species of 25,000 molecular weight. The hydrolases from both strains have similar Km values, pH optima, and thermal labilities and attack the same range of substrates. Neither hydrolase was stimulated by Mg2+ or Mn2+, and both were inhibited by p-chloromercuribenzoate and iodoacetamide. Immunodiffusion studies with the purified enzymes and antibodies formed against them show some cross-reaction of Pseudomonas NCIB 9865 enzymes with antibodies to Pseudomonas NCIB 10015, but not vice versa.

Immunological comparison of enzymes of the beta-ketoadipate pathway

beta-Carboxy-cis,cis-muconate lactonizing enzyme and gamma-carboxymuconolactone decarboxylase catalyze sequential reactions in the beta-ketoadipate pathway; the subunit sizes of the enzymes from Pseudomonas putida, biotype A, are 40 000 and 13 000, respectively. The cross reaction of antisera prepared against the enzymes was tested with the isofunctional enzymes formed by representatives of other bacterial species. Despite the differences in the subunit sizes of the enzymes, the antisera revealed the same general pattern: cross reaction was observed with the corresponding enzymes formed by other strains in the fluorescent Pseudomonas RNA homology group I and generally was not observed with enzymes from other Pseudomonas species or from other bacterial genera. Exceptions were provided by representatives of Pseudomonas cepacia. Members of this species are classified outside the fluorescent Pseudomonas RNA homology group. Nevertheless, the gamma-carboxymuconolactone decarboxylases from these organisms formed precipitin bands with antisera prepared against the corresponding enzyme from P.putida, biotype A; the lactonizing enzymes from the two species did not appear to cross react. Immunodiffusion experiments with gamma-carboxymuconolactone decarboxylase indicated that a common set of antigenic determinants for the enzyme is conserved among strains that have been classified together by other criteria; the relative immunological distances of the decarboxylases of each taxon from the reference P.putida, biotype A, enzyme were indicated by spurring patterns on Ouchterlony plates. These results suggested that the interspecific transfer of the structural gene for the enzyme is not a common event in Pseudomonas.