Expression of acylamidase gene in Rhodococcus erythropolis strains

The expression of a new acylamidase gene from R. erythropolis TA37 was studied in Rhodococcus erythropolis strains. This acylamidase, as a result of its unique substrate specificity, can hydrolyse N-substituted amides (4′-nitroacetanilide, N-isopropylacrylamide, N′N-dimethylaminopropylacrylamide). A new expression system based on the use of the promoter region of nitrile hydratase genes from R. rhodochrous M8 was created to achieve constitutive synthesis of acylamidase in R. erythropolis cells. A fourfold improvement in the acylamidase activity of recombinant R. erythropolis cells as compared with the parent wild-type strain was obtained through the use of the new expression system.     

Cloning of new acylamidase gene from Rhodococcus erythropolis and its expression in Escherichia coli

The gene for new Rhodococcus erythropolis TA37 acylamidase, which possesses unique substrate specificity, has been cloned and expressed in E. coli. Substrates for this enzyme are not only simple amides, such as acetamide and propionamide, but also N-substituted amides, such as 4′-nitroacetanilide. The 1431-bp gene was expressed in E. coli BL21 (DE3) cells on pET16b plasmid under the control of a promoter of the ? 10 gene from the T7 phage. The molecular mass of recombinant acylamidase in E. coli was 55 kDa, which corresponded to that of native acylamidase from Rhodococcus erythropolis TA37. Recombinant acylamidase was able to hydrolize N-substituted amides. A search of a nucleotide database and multiple alignment revealed that acylamidase belonged to the Amidase protein family PF01425, but its nucleotide and amino acid sequences differed significantly from those of the described amidases.     

The remarkable Rhodococcus erythropolis

Rhodococcus erythropolis cells contain a large set of enzymes that allow them to carry out an enormous number of bioconversions and degradations. Oxidations, dehydrogenations, epoxidations, hydrolysis, hydroxylations, dehalogenations and desulfurisations have been reported to be performed by R. erythropolis cells or enzymes. This large array of enzymes fully justifies the prospective application of this bacterium in biotechnology.     

Isobutylidenediurea degradation by Rhodococcus erythropolis

A new enzyme (isobutylidenediurea amidinohydrolase) catalyzing the hydrolysis of isobutylidenediurea (a condensation product of urea and isobutyraldehyde widely used as a slow-release nitrogeneous fertilizer) was characterized from a strain of Rhodococcus erythropolis. The enzyme was purified 1250-fold to apparent homogeneity and shown to hydrolyze the fertilizer to urea and isobutyraldehyde at a molar ratio of 2 : 1. No activity was observed with ureido- or other structurally related compounds. Its molecular mass was determined by native polyacrylamide gelelectrophoresis and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry to be 15 kDa (±2 kDa) and 16.4 kDa, respectively. Growth of the bacterium in the presence of isobutylidenediurea led to an increased expression of the constitutively synthetized enzyme.     

Characterization of IS1676 from Rhodococcus erythropolis SQ1

To develop a transposable element-based system for mutagenesis in Rhodococcus, we used the sacB gene from Bacillus subtilis to isolate a novel transposable element, IS1676, from R. erythropolis SQ1. This 1693 bp insertion sequence is bounded by imperfect (10 out of 13 bp) inverted repeats and it creates 4 bp direct repeats upon insertion. Comparison of multiple insertion sites reveals a preference for the sequence 5′-(C/T)TA(A/G)-3′ in the target site. IS1676 contains a single, large (1446 bp) open reading frame with coding potential for a protein of 482 amino acids. IS1676 may be similar to an ancestral transposable element that gave rise to repetitive sequences identified in clinical isolates of Mycobacteriumkansasii. Derivatives of IS1676 should be useful for analysis of Rhodococcus strains, for which few other genetic tools are currently available. Received: 1 April 1999 / Received revision: 6 July 1999 / Accepted: 1 August 1999     

A Long-Chain Secondary Alcohol Dehydrogenase from Rhodococcus erythropolis ATCC 4277

A NAD-dependent secondary alcohol dehydrogenase has been purified from the alkane-degrading bacterium, Rhodococcus erythropolis ATCC 4277. The enzyme was found to be active against a broad range of substrates, particularly long-chain secondary aliphatic alcohols. Although optimal activity was observed with linear 2-alcohols containing between 6 and 11 carbon atoms, secondary alcohols as long as 2-tetradecanol were oxidized at 25% of the rate seen with mid-range alcohols. The purified enzyme was specific for the S-(+) stereoisomer of 2-octanol and had a specific activity for 2-octanol of over 200 (mu)mol/min/mg of protein at pH 9 and 37(deg)C, 25-fold higher than that of any previously reported S-(+) secondary alcohol dehydrogenase. Linear primary alcohols containing between 3 and 13 carbon atoms were utilized 20- to 40-fold less efficiently than the corresponding secondary alcohols. The apparent K(infm) value for NAD(sup+) with 2-octanol as the substrate was 260 (mu)M, whereas the apparent K(infm) values for the 2-alcohols ranged from over 5 mM for 2-pentanol to less than 2 (mu)M for 2-tetradecanol. The enzyme showed moderate thermostability (half-life of 4 h at 60(deg)C) and could potentially be useful for the synthesis of optically pure stereoisomers of secondary alcohols.     

Molecular Genetic Markers for Identification of Rhodococcus erythropolis and Rhodococcus qingshengii

Microbiology - The application of restriction analysis of amplification products of the genes rpoC and alkB, encoding the synthesis of the DNA-dependent RNA polymerase β'-subunit and...     

Characterization of catechol catabolic genes from Rhodococcus erythropolis 1CP.

The biochemical characterization of the muconate and the chloromuconate cycloisomerases of the chlorophenol-utilizing Rhodococcus erythropolis strain 1CP previously indicated that efficient chloromuconate conversion among the gram-positive bacteria might have evolved independently of that among gram-negative bacteria. Based on sequences of the N terminus and of tryptic peptides of the muconate cycloisomerase, a fragment of the corresponding gene has now been amplified and used as a probe for the cloning of catechol catabolic genes from R. erythropolis. The clone thus obtained expressed catechol 1,2-dioxygenase, muconate cycloisomerase, and muconolactone isomerase activities. Sequencing of the insert on the recombinant plasmid pRER1 revealed that the genes are transcribed in the order catA catB catC. Open reading frames downstream of catC may have a function in carbohydrate metabolism. The predicted protein sequence of the catechol 1,2-dioxygenase was identical to the one from Arthrobacter sp. strain mA3 in 59% of the positions. The chlorocatechol 1,2-dioxygenases and the chloromuconate cycloisomerases of gram-negative bacteria appear to be more closely related to the catechol 1,2-dioxygenases and muconate cycloisomerases of the gram-positive strains than to the corresponding enzymes of gram-negative bacteria.     

Acetonitrile-hydrolysing enzymes in Rhodococcus erythropolis A10

Rhodococcus erythropolis A10 metabolizes acetonitrile by a two step process involving nitrile hydratase (NHase) and amidase. Both the enzymes were inducible and low basal levels of activities were observed in the cells grown in the absence of acetonitrile (AN). Cobalt and iron enhanced NHase, while amidase showed iron dependence. Presence of glucose or ammonium sulphate (AS) failed to affect acetonitrile utilization.     

Dienelactone hydrolase from Rhodococcus erythropolis 1 CP: purification and properties

Dienelactone hydrolases (EC 3.1.1.45) have been shown to play an indispensable role in the degradation of chloroaromatic compounds via ortho-cleavage of chlorocatechols. We report on the purification of dienelactone hydrolase of the chlorophenol-utilizing strain Rhodococcus erythropolis 1CP to apparent homogeneity. Dienelactone hydrolase differed fron the corresponding enzymes of other chloroaromatic compound-catabolizing strains in being restricted to substrates with a cis-dienelactone structure. From the cis-dienelactone-hydrolyzing enzyme of a 4-fluorobenzoate-utilizing Burkholderia (Pseudomonas) cepacia strain, it differed considerably in properties such as pH optimum of activity, inhibition by p-chloromercuribenzoate, and amino acid composition. Thus, there is not necessarily a close relationship between substrate specificity and other properties of dienelactone hydrolases.     

Degradation of aromatic amino acids by Rhodococcus erythropolis

A Gram-positive Rhodococcus erythropolis strain S1 was shown to assimilate aromatic amino acids such as L-phenylalanine, L-tyrosine, L-tryptophan, D-phenylalanine, D-tyrosine and D-tryptophan, which were utilized not only as the sole carbon source but also as a suitable nitrogen source. The highest growth on these aromatic amino acids occurred at a temperature of 30°C. L-Phenylalanine, L-tyrosine and L-tryptophan degradative pathways would appear to be independent, and to be induced alternatively. The strain S1 also showed the ability to assimilate peptides which consisted of only L-phenylalanine and L-tyrosine.     

Biological properties of the alpha-mannanase of Rhodococcus erythropolis

When Rhodococcus erythropolis is cultivated under the submerged conditions in a medium containing yeast mannan as a sole carbon source, it synthesizes exocellular alpha-mannanase which hydrolyzes alpha-1,2 and alpha-1,3 bonds in a mannan molecule. The alpha-mannanase of R. erythropolis exerts distinct lectin properties under the conditions which entirely exclude its enzyme activity.     

Isolation and characterization of a haloalkane halidohydrolase from Rhodococcus erythropolis Y2

Rhodococcus erythropolis strain Y2, isolated from soil by enrichment culture using 1-chlorobutane, was able to utilize a range of halogenated aliphatic compounds as sole sources of carbon and energy. The ability to utilize 1-chlorobutane was conferred by a single halidohydrolase-type haloalkane dehalogenase. The presence of the single enzyme in cell-free extracts was demonstrated by activity strain polyacrylamide gel electrophoresis. The purified enzyme was a monomeric protein with a relative molecular mass of 34 kDa and demonstrated activity against a broad range of haloalkanes, haloalcohols and haloethers. The highest activity was found towards alpha, omega disubstituted chloro- and bromo- C2-C6 alkanes and 4-chlorobutanol. The Km value of the enzyme for 1-chlorobutane was 0.26 mM. A comparison of the R. erythropolis Y2 haloalkane halidohydrolase with other haloalkane dehalogenases is discussed on the basis of biochemical properties and N-terminal amino acid sequence data.     

Purification and Properties of Gentisate 1,2-Dioxygenase from Rhodococcus erythropolis S-1

Gentisate 1,2-dioxygenase, which participates in salicylate and m-hydroxybenzoate metabolism, was purified from cell-free extracts of Rhodococcus erythropolis S-1, a Gram-positive bacterium. The purified enzyme gave a single band on native PAGE and SDS–PAGE. The molecular mass of the enzyme was estimated to be 328 kDa. The structure of the enzyme appears to be an octamer of identical subunits. The enzyme from this bacterium was similar in general enzymatic properties to a gentisate 1,2-dioxygenase from a Gram-negative bacterium except for molecular mass and structure.     

Production of 3,4-dihydroxyphthalate from phthalate by a membrane-bound two-enzyme system from Rhodococcus erythropolis

 Gram-positive Rhodococcus erythropolis strain S1 formed enzymes for the degradation of phthalate when grown in a phthalate-containing minimal medium. The membrane fraction prepared from phthalate-grown cells by ultrasonication converted phthalate to protocatechuate as the final product. Using two membrane-bound enzymes, phthalate 3,4-dioxygenase (PO) and 3,4-dihydro-3,4-dihydroxyphthalate 3,4-dehydrogenase (PH), prepared by solubilization of the membrane fraction, 3,4-dihydroxyphthalate was selectively obtained from phthalata. Fe²⁺ and Mn²⁺ stimulated the formation of 3,4-dihydroxyphthalate by the membrane-bound PO and PH system. Received: 27 April 1994/Received last revision: 19 August 1994/Accepted: 12 September 1994     

Biochemical identification and biophysical characterization of a channel-forming protein from Rhodococcus erythropolis

Organic solvent extracts of whole cells of the gram-positive bacterium Rhodococcus erythropolis contain a channel-forming protein. It was identified by lipid bilayer experiments and purified to homogeneity by preparative sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE). The pure protein had a rather low molecular mass of about 8.4 kDa, as judged by SDS-PAGE. SDS-resistant oligomers with a molecular mass of 67 kDa were also observed, suggesting that the channel is formed by a protein oligomer. The monomer was subjected to partial protein sequencing, and 45 amino acids were resolved. According to the partial sequence, the sequence has no significant homology to known protein sequences. To check whether the channel was indeed localized in the cell wall, the cell wall fraction was separated from the cytoplasmic membrane by sucrose step gradient centrifugation. The highest channel-forming activity was found in the cell wall fraction. The purified protein formed large ion-permeable channels in lipid bilayer membranes with a single-channel conductance of 6.0 nS in 1 M KCl. Zero-current membrane potential measurements with different salts suggested that the channel of R. erythropolis was highly cation selective because of negative charges localized at the channel mouth. The correction of single-channel conductance data for negatively charged point charges and the Renkin correction factor suggested that the diameter of the cell wall channel is about 2.0 nm. The channel-forming properties of the cell wall channel of R. erythropolis were compared with those of other members of the mycolata. These channels have common features because they form large, water-filled channels that contain net point charges.