Identification of interaction site of pseudoazurin with its redox partner, copper-containing nitrite reductase from Alcaligenes faecalis S-6

Pseudoazurin, a low molecular weight protein containing a single type I copper, functions as an electron donor to a copper-containing nitrite reductase (NIR) in a denitrifying bacterium Alcaligenes faecalis S-6. To elucidate the protein-protein interaction between these two copper-containing proteins, each of nine out of 13 lysine residues on the surface of pseudoazurin were independently replaced by alanine or aspartate, and the effects of the mutations on the interaction with NIR, as well as the physicochemical properties of pseudoazurin, were analyzed. All of the mutated pseudoazurins showed optical spectra and oxidation-reduction potentials almost identical to those of wild-type pseudoazurin, suggesting that none of the replacements of these lysine residues affected the environment around the type I copper site. Kinetic analysis of electron transfer between mutated pseudoazurins and NIR reveals that the lysine mutations have very little effect on the rate of electron transfer to NIR, but substitution at residues 10, 38, 57 and 77, all close to the copper site, substantially decreases the affinity of pseudoazurin for NIR. This suggests that pseudoazurin interacts with NIR through the region close to the type I copper site. The refined X-ray structures of Lys38Asp and Lys10Asp/Lys38Asp show that the molecular structure has indeed changed little. A new space group is observed for the Lys109Ala mutant crystal. Crystal packing interactions change for the Lys10Asp/Lys38Asp mutant but remain the same for Lys38Asp and Lys59Ala mutants.

Carcinoembryonic antigen levels in the peritoneal cavity: useful guide to peritoneal recurrence and prognosis for gastric cancer

At the time of laparotomy, peritoneal washings were collected from 155 gastric cancer patients and the levels of carcinoembryonic antigen (CEA) determined. The CEA levels in peritoneal washings were statistically independent of those in sera and could more reliably predict the presence of peritoneal metastasis than a cytologic study. Peritoneal recurrence was seen in 14 of 118 patients after curative operation. Of the 14 patients, 10 (71%) had elevated levels of CEA (100 ng/g protein) at surgery. Of these 10 cases, 2 of the tumors were classified as stage IB and 4 had no serosal invasion. Only one patient with peritoneal metastasis and a low CEA level was free from relapse more than 1 year after operation. Kaplan-Meier's analysis showed that a high CEA level in peritoneal washings was a predictor of poor prognosis in patients who underwent either curative or noncurative resection. A proportional hazards regression analysis showed that a high CEA level in peritoneal washings was statistically significant in terms of predicting a shorter interval until peritoneal recurrence (p = 0.0002) and for survival (p = 0.0001). The CEA level in peritoneal washings is therefore of value as an indicator of peritoneal recurrence and prognosis.

Involvement of the COOH-terminal pro-sequence of Serratia marcescens serine protease in the folding of the mature enzyme

The serine protease (SSP) from a Gram-negative organism, Serratia marcescens, is excreted even from Escherichia coli. The protease is synthesized as a 1045-amino-acid precursor (preproSSP) composed of three functional portions, a typical NH2-terminal signal peptide of 27 amino acids, the mature protease part of 618 amino acids, and a large COOH-terminal part of 400 amino acids. After the mature part (Ala28 to Asp645) has been liberated into the medium, most of the COOH-terminal part (Phe717 to Phe1045) remains stably in the outer membrane. When a mutated gene encoding the prepro-SSP with deletion of the junction region (Ser646 to Gly716) between the mature protease and the processed COOH-terminal protein was expressed in E. coli, the SSP protein was not detected in any fractions of the cells nor in the medium, whereas a processed COOH-terminal protein was found in the outer membrane. However, when the outer membrane fraction prepared from the transformant exhibiting the junction region (Ser646 to Gly716) probably on the cell surface was co-cultured with the transformant, SSP was found in the medium. Furthermore, a significant portion of the SSP protein denatured with guanidine hydrochloride was correctly refolded in vitro into the active protease, only in the presence of the outer membrane preparation from the transformant exhibiting the junction region. These results suggest that the junction region is exposed outside the cells, and it plays a role for guiding the folding of SSP in the correct conformation.

Clear cell adenocarcinoma of the vagina in a young female, treated by combination chemotherapy (local and systemic chemotherapy), complicated with chromosomal abnormality

Although cancer of the vagina, a rare form of genital cancer, is usually squamous cell carcinoma in women over the age of 50 years, vaginal clear cell adenocarcinomas (CCA) are exceedingly rare. The pathogenesis of clear cell adenocarcinoma is uncertain, but as a clinical entity, it is most commonly associated with diethylstilbestrol exposure in utero. We report a rare case of primary vaginal CCA in a 17-year-old female who was not exposed to diethylstilbesterol in utero. The case, which was complicated with chromosomal abnormality, was treated with combination chemotherapy. To our knowledge, this is the first reported case of vaginal CCA in a woman with chromosomal abnormality and bicornate uterus.

Nitrile hydratase gene from Rhodococcus sp. N-774 requirement for its downstream region for efficient expression

For improvement of the production of nitrile hydratase (NHase) from Rhodococcus sp. N-774 by recombinant DNA techniques, several plasmids, each of which had a deletion of the upstream or downstream region of the genes encoding the alpha and beta subunits of NHase, were constructed. Enzyme assays of recombinant R. rhodochrous and Escherichia coli cells showed that a downstream region of the NHase genes was indispensable for the production of active NHase in both cells, but for the production of the active amidase, no genes other than the amidase structural gene were required. The nucleotide sequence of the downstream region contained a single open reading frame (Orf1188) with 396 amino acids. Orf1188 showed similarity in amino acid sequence to P47K, an open reading frame found downstream of the NHase genes from Pseudomonas chlororaphis B23, and also to the cobW gene product, which may be involved in cobalamin biosynthesis in Pseudomonas denitrificans. Because the distance between the TGA stop codon for the NHase beta-subunit and the ATG codon for Orf1188 is only 98 bp, and because production of both Orf1188 and NHase is dependent on a promoter upstream of the amidase gene, these genes appear to be co-transcribed in a polycistronic manner, forming an operon. By optimization of the culture conditions of R. rhodochrous carrying pKRNH2, which contained the amidase, NHase, and Orf1188 genes, the transformant showed the NHase activity 6-fold higher than that of the original strain, Rhodococcus sp. N-774.

[The risk factors of lymph node metastasis in submucosal invasive gastric carcinoma--assessment of the indication for endoscopic treatment]

Recent advances in endoscopic diagnosis and treatments have increased the number of early gastric carcinomas being treated by endoscopic resection. However, the appropriate criteria for endoscopic resection of gastric carcinomas with submucosal invasion are not completely established. During the past 12 years from 1980 to 1992, 116 lesions in 116 patients were treated by surgical operation for differentiated type submucosal invasive gastric carcinoma. In this study, the risk factors of lymph node metastasis were investigated clinicopathologically. As the result, 1) Heterogeneity of submucosal invasive tumor margin was demonstrated in 19 (16%) of the 116 lesions of which predominant histology was differentiated adenocarcinoma. 2) Lymph node metastasis was demonstrated in 16 (16%) of the 97 lesions of which histology was differentiated type. 3) Significant risk factors of lymph node metastasis was demonstrated in submucosal massive invasion (sm3), papillary adenocarcinoma, INF gamma, lymph vessel involvement (ly(+)), and existence of ulcer (ul(+)). 4) Sm3 and papillary adenocarcinoma (pap) had a higher malignant potential than ly(+), INF gamma, and ul(+) by multivariate analysis using the logistic regression. 5) All lesions with both well differentiated adenocarcinoma (tub1) and sm minimal invasion (sm1) had no lymph node metastasis. These results suggested that the lesions with both well differentiated adenocarcinoma tub1 and sm1, which have no other risk factors such as ly(+), INF gamma, and ul(+), may be considered as the appropriate indication for endoscopic treatment of gastric submucosal carcinoma.

Substrate-dependent change in the pH-activity profile of alkaline endo-1,4-beta-glucanase from an alkaline Bacillus sp

A neutral cellulase (BSC) from Bacillus subtilis and an alkaline cellulase (NK1) from alkalophilic Bacillus sp. N-4 show significant amino acid sequence homology. Despite the high homology, the pH-activity profiles of the two enzymes for carboxymethyl cellulose (CMC) hydrolysis are quite different; BSC shows a sharp optimum pH at 6, whereas NK1 shows its full activity in a broad range, from pH 6 to 10.5. For elucidation of the reasons for the difference in their pH-activity profiles, their activities were examined at various pHs using a series of cellooligosaccharides and their derivatives, cellotetraose (G4), cellopentaose (G5), cellohexaose (G6), cellopentaitol (G5OH), and cellohexaitol (G6OH), as substrates. The optimum pH of BSC was around 6 for all the cellooligosaccharides examined. On the other hand, the optimum pH of NK1 varied depending on the substrate, i.e., a sharp optimum at pH 6 with G4 and G5OH, and a broad optimum of pH 6 to 10.5 with G5, G6, and G6OH. Comparison of the kinetic parameters of the two cellulases at pH 7 and 9 using G6OH as a substrate revealed that NK1 showed similar values at both pHs, while BSC showed a greatly increased Km value for this substrate at pH 9. In addition, NK1 showed a greatly increased Km value for G5OH hydrolysis at pH 9. Both enzymes cleaved these substrates at the same position, which suggests the same productive binding mode of these substrates with both enzymes. All these observations suggest that the reduced enzyme activity of BSC in the alkaline pH range can be attributed to a decrease in the affinity of a subsite for the third glucose moiety from the scissile site of these substrates.

Expression of insulin receptor substrate-1 in hepatocytes: an investigation using monoclonal antibodies

To investigate the expression and subcellular distribution of insulin receptor substrate-1 in hepatocytes, which are major targets of insulin along with muscle and adipose tissue, we obtained monoclonal antibodies by immunizing mice with a fusion protein consisting of the C-terminal portion of the human insulin receptor substrate-1 and glutathione-S-transferase. Two of the monoclonal antibodies (designated as 7B3 and 6G5) were found to be useful for immunohistochemical studies. Using 6G5 we demonstrate a high level of expression of insulin receptor substrate-1 in liver cirrhosis hepatocytes and variable expression in hepatocellular carcinoma cells. These results suggest that insulin receptor substrate-1 may play a role in liver regeneration during cirrhosis and that an insulin signaling cascade may be involved in hepatocarcinogenesis.

Basic properties of an alginate impression material supplemented with chlorhexidine. I. Disinfectant effects on oral microbes

To examine the disinfectant effects on oral microbes of an alginate impression material supplemented with 1% chlorhexidine as the aseptic ingredient (Coe Hydrophilic Gel, CHG), several cell suspensions of oral microbes (3 Gram-positives, 2 Gram-negatives and 1 yeast) were exposed to the surface of cast CHG or that of a control impression material for 5 or 30 min. They were then transferred to the surfaces of agar plates. Colony formation was estimated after culture for several incubation periods. No growth of bacteria on the plates was observed when the suspensions had been exposed to CHG even for 5 min, whereas for the control material, all the bacteria formed colonies. The yeast showed colony formation irrespective of the kind of impression material and the duration of exposure. Thus, it appears that use of an impression material supplemented with 1% chlorhexidine such as CHG may protect clinical staff and dental technicians from possible bacterial infections associated with the impression procedures.

X-ray structure and site-directed mutagenesis of a nitrite reductase from Alcaligenes faecalis S-6: roles of two copper atoms in nitrite reduction

Nitrite reductase (NIR) from the denitrifying bacterium Alcaligenes faecalis S-6 is a copper-containing enzyme which requires pseudoazurin, a low molecular weight protein containing a single type I copper atom, as a direct electron donor in vivo. Crystallographic analysis shows that NIR is a trimer composed of three identical subunits, each of which contains one atom of type I copper and one atom of type II copper, and that the ligands to the type I and type II copper atoms are the same as those of the Achromobacter cycloclastes NIR. An efficient NIR expression-secretion system in Escherichia coli was constructed and used for site-directed mutagenesis. An NIR mutant with a replacement of the type II copper ligand, His135, by Lys still retained a type II copper site as well as a type I copper atom, but it completely lost nitrite-reducing activity as measured with methyl viologen as an electron donor. On the other hand, another mutant with a replacement of the type I copper ligand, Met150, by Glu contained only a type II copper atom, but it still retained significant nitrite-reducing activity with methyl viologen. When pseudoazurin was used as an electron donor for the reaction, however, Met150Glu failed to catalyze the reduction of nitrite. Kinetic analysis of the electron transfer between NIR and pseudoazurin revealed that the electron-transfer rate between Met150Glu and pseudoazurin was reduced 1000-fold relative to that of wild-type NIR.(ABSTRACT TRUNCATED AT 250 WORDS)

Study on the castability of Co-Cr alloy for cast plates. Part 4. Effects of sectional area, number of sprues and alloy components on castability

Co-Cr alloy is used more frequently than Ni-Cr alloy as a nonprecious alloy for cast plates in Japan. Titanium with good biocompatibility has often been contained in the composition of this Co-Cr alloy. However, since the melting temperature of Co-Cr alloy is very high, about 1300 degrees C, and it oxidizes easily, a vacuum-pressure casting machine capable of melting this alloy in a reduced atmosphere has recently been developed. In this study, using the vacuum-pressure casting machine, the possible effects of sectional area and the number of sprues attached to the cast plate wax pattern, as well as the alloy components, on the castability of three kinds of Co-Cr alloy containing titanium were examined. It was found that all of these parameters had significant effects on Co-Cr alloy castability.

Mutation of a fungal aspartic proteinase, Mucor pusillus rennin, to decrease thermostability for use as a milk coagulant

Mutagenesis of a fungus Mucor pusillus, a producer of an aspartic proteinase named Mucor pusillus rennin (MPR), was performed to obtain the mutated enzymes with decreased thermostability, which is desirable for practical use of the enzyme as a milk coagulant for cheese manufacturing. A fungal mutant strain which produced the mutant enzyme with distinctly reduced thermostability was isolated. Two different mutant alleles of the mpr gene, one with a single amino acid exchange of Ala101 for Thr and the other of Gly186 for Asp, were cloned out of this mutant strain. The mutated mpr genes were expressed in Saccharomyces cerevisiae under the control of the yeast GAL7 promoter to produce the active enzymes in extracellular medium. Both of the mutations, especially Gly186Asp, were confirmed to cause a marked decrease in thermostability of the enzyme. All mutants possessing exchanges of Gly186 for various amino acids by site-directed mutagenesis showed a decrease in thermostability, indicating involvement of this residue to maintain a conformation of the enzyme. A double mutant having the both exchanges, Ala101Thr and Gly186Asp, in a single molecule showed the lowest thermostability without decrease in the enzymatic activity as well as the relative ratio of clotting to proteolytic activity.

The acceptability of prenatal diagnosis in Japan

Prenatal diagnosis has been performed more frequently in Japan recently, but is still less popular than in the United States or Europe. Legal arrangements, insufficient economic support, and insufficient medical information provided to future parents may explain this difference. The acceptability of prenatal diagnosis, based on the concept of the cost of side effects and elective abortion, was found to be similar when examined through decision analysis and direct survey. Amniocentesis was considered useful for more than half of couples in Japan when the incidence of chromosomal abnormality is more than 0.5% and proper information about the decision to undergo this examination is provided to the pregnant woman and her family.

[Prolongation and recovery under sevoflurane anesthesia of neuromuscular blocking action of vecuronium]

Thirty-seven patients (ASA I or II) undergoing elective abdominal surgery were randomly allocated to four groups, which were anesthetized with nitrous oxide 67%, oxygen 33% and sevoflurane 0%, 1%, 2% and 3% respectively. We administered clinically used doses of vecuronium for abdominal surgery and studied the duration (the time from 100% block after injection to 20% recovery) and the recovery time (time from the last injection of vecuronium to 20% recovery). No prolongation of neuromuscular blocking effect was demonstrated with the initial dose of vecuronium. Significant prolongations of the duration and the recovery time were demonstrated with the maintenance dose of vecuronium only with sevoflurane over 2% and the effect was concentration-dependent.

Basic studies of radiopaque resin monomer (III). Physical properties of trial composite resins

A series of studies has been conducted on the synthesis of radiopaque monomers and the development of a composite resin having these monomers. Using octachlorocyclotetraphosphazene, P4N4Cl8 (4PNC), three kinds of radiopaque cyclophosphazene monomers, 4PN(Br3Ph)1-3-(EMA)7-5, were synthesized by reacting 1-3 mols of tribromophenol (Br3Ph) and 7-5 mols of 2-hydroxyethyl methacrylate (HEMA). As the monomer for an organic composite filler, 70% (wt) synthesized monomer was used with silica (OX-50) treated with silane mixed at 30% and ground after heat-polymerization and then run through a 325-mesh sieve after polymerization. As a base monomer, 25% urethane monomer (U-2TH) was mixed in 25% synthesized monomer and photosensitizer was added. The composite resin was prepared by mixing 50% organic composite filler with 50% base monomer, and polymerized with a Dentacolor XS (Kulzer) visible light-curing apparatus by irradiation for 90 s on each side, 180 s in total. Mechanical properties did not vary with the increase in the number of tribromophenol replacements. Compressive yield strength was more than 120 MPa in all cases. Transverse strength was 60-75 MPa and hardness was HK 26-30. However, the aluminum equivalent increased with the increase in the number of tribromophenol replacements. In the case of 4PN-(Br3Ph)3, the value was 8.8 mm, whereas in the case of commercial composite resin, it was 0.4-10.4 mm.

Thermal properties of glass ionomer cement

Five currently available glass ionomer cements (BASE CEMENT, DENTIN CEMENT, HY-BOND GLAS IONOMER-F, KETAC CEM, TOKUSO IONOMER) were studied with regard to the relationship between thermal properties and powder-liquid ratio (P/L ratio). The experiments were performed using five different P/L ratio of 0.8, 0.9, 1.0, 1.1 and 1.2 (P/L = 1.0: manufacturer's instruction) and measured with a xenon flash thermal-constant measuring device. Thermal diffusivity of the glass ionomer cements ranged from 0.212 to 0.303 x 10(-2) cm2 s-1; it increased according to the increase in the P/L ratio. The specific thermal capacity of the glass ionomer cements ranged from 1.011 to 1.369 Jg-1 K-1; it decreased with the increase in the P/L ratio. Thermal conductivity of the glass ionomer cements ranged from 0.505 to 0.712 Wm-1 K-1; it increased according to the increase in the P/L ratio.

Stromelysin-3 mRNA expression and malignancy: comparison with clinicopathological features and type IV collagenase mRNA expression in breast tumors

mRNA expression of stromelysin-3 (ST3) and 72K type IV collagenase (cIVase) in 4 human breast cancer cell lines and 55 resected breast tumors were examined using Northern blot analysis. In 4 cell lines ST3 was not expressed at all, while cIVase gene expression was detected in 3 of them. The ST3 expression was found more specifically in malignant tumors (39/40, 97.5%) than in benign ones (4/15, 26.7%), although cIVase was expressed in all tumor specimens. The quantitative analysis showed that ST3 expression in malignancies was significantly greater than that in benign tumors (P = 0.0007), while cIVase expression was not (P = 0.1381). ST3 gene expression was also closely related to the presence of lymph node metastasis (P = 0.047), while cIVase was not (P = 0.1091). These results suggest, therefore, that ST3 is expressed more specifically by stromal cells surrounding cancer cells than cIVase. Since ST3 mRNA expression was independent of the EGFR, ER and erbB2 protein expression, ST3 may be a new potent prognostic guide for breast carcinomas, which can detect highly malignant subpopulations.

Amidase coupled with low-molecular-mass nitrile hydratase from Rhodococcus rhodochrous J1. Sequencing and expression of the gene and purification and characterization of the gene product

The cloned 9.4-kb insert of plasmid pNHJ20L containing low-molecular-mass nitrile hydratase (L-NHase) gene from Rhodococcus rhodochrous J1 [Kobayashi, M. et al. (1991) Biochim. Biophys. Acta 1129, 23-33] was digested with various restriction enzymes, and the trimmed fragments were inserted into pUC18 or pUC19. A 1.96-kb EcoRI-SphI region located 1.9-kb downstream of the L-NHase gene was found to be essential for the expression of amidase activity in Escherichia coli; the gene arrangement of the amidase and the NHase in R. rhodochrous J1 differed from those in Rhodococcus species including N-774 and Pseudomonas chlororaphis B23. The nucleotide-determined sequence indicated that the amidase consists of 515 amino acids (54626 Da) and the deduced amino acid sequence of the amidase had high similarity to those of amidases from Rhodococcus species including N-774 and P. chlororaphis B23 and to indole-3-acetamide hydrolase from Pseudomonas savastanoi. The amidase gene modified in the nucleotide sequence upstream from its start codon expressed 8% of the total soluble protein in E. coli under the control of lac promoter. The level of amidase activity in cell-free extracts of E. coli was 0.468 unit/mg using benzamide as a substrate. This amidase was purified to homogeneity from extracts of the E. coli transformant with 30.4% overall recovery. The molecular mass of the enzyme estimated by HPLC was about 110 kDa and the enzyme consists of two subunits identical in molecular mass (55 kDa). The enzyme acted upon aliphatic amides such as propionamide and also upon aromatic amides such as benzamide. The apparent Km values for propionamide and benzamide were 0.48 mM and 0.15 mM, respectively. This amidase was highly specific for the S-enantiomer of 2-phenylpropionamide, but could not recognize the configuration of 2-chloropropionamide. It also catalyzed the transfer of an acyl group from an amide to hydroxylamine to produce the corresponding hydroxamate.

Distribution of intrathecally administered ACNU in mongrel dogs: pharmacokinetics and quantitative autoradiographic study

The pharmacokinetics of 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea (ACNU) in the cerebrospinal fluid (CSF), were determined in dogs after ventriculolumbar perfusion (VLP, n = 6), and bolus injection into the ventricle (VB, n = 2), cisterna magna (MB, n = 5), and lumbar cistern (LB, n = 3), by high-performance liquid chromatography. The VLP method introduced effective amounts of ACNU into the lumbar cistern for cell kill in vitro. That is, the areas under the time concentration curve (AUC) of ACNU in the lumbar CSF for those receiving a 1.5 mg perfusion of ACNU were 481, 791, and 520 micrograms.min/ml and those receiving a 5 mg perfusion were 1,081, 2,048, and 1,215 micrograms.min/ml, respectively. These values were superior to 3-log cell kill condition of 9L gliosarcoma and 1.5-log cell kill of HU-126 human glioma cell line. Among the groups to which 5 mg of ACNU was administered, the VLP method attained significantly higher AUC values in the lumbar CSF than MB method. Quantitative autoradiography using an imaging plate system was performed in the VLP group (n = 2), VB group (n = 1), MB group (n = 2), and LB group (n = 2) using a 10 microCi/kg [ethylene-14C] ACNU dose which is thought to be related to the alkylating activity of ACNU. The VLP method attained a stable and abundant distribution of ACNU in the neural axis from the ventricular cavity to the lumbar cistern, but the cerebral convexity surface was devoid of a significant level of ACNU. When the MB method was used, the pharmacokinetic data varied in the cisterna magna and lumbar region, and again no significant level of ACNU was detected in the ventricular cavity. With the LB method, although a rich distribution was detected in the spinal cord, the concentration decreased abruptly at the upper cervical level. The VB method was unsatisfactory for obtaining an effective amount of ACNU in the lumbar region. The research and testing to date indicate that the VLP method is the procedure of choice in the treatment of meningeal dissemination.

Characterization of nitrile hydratase genes cloned by DNA screening from Rhodococcus erythropolis

Southern hybridization analysis using the genes encoding the alpha- and beta-subunits of nitrile hydratase (NHase) from Rhodococcus sp. N-774 as probe suggested that two R. erythropolis strains, JCM6823 and JCM2892, among 31 strains mainly from Japan Culture of Microorganisms (JCM) have NHase genes. Restriction analysis of DNA fragments showing positive hybridization showed that each fragment carried a nucleotide sequence very similar to that of the NHase genes from Rhodococcus sp. N-774. Nucleotide sequence analysis of the DNA fragment cloned from R. erythropolis JCM6823 showed the presence of the genes encoding the alpha- and beta-subunits of NHase, which show 94.7% and 96.2% identity in amino acid sequence to those of Rhodococcus sp. N-774, respectively, as well as a C-terminal portion of the amidase gene upstream from these genes. Despite the extremely high amino acid sequence similarity in both NHases and amidases from R. erythropolis JCM6823 and Rhodococcus sp. N-774, the NHases and amidases from R. erythropolis strains showed broader substrate specificity when compared to those from Rhodococcus sp. N-774. This suggests that a very limited number of amino acid residues are responsible for the difference in substrate specificity. Although the NHase of Rhodococcus sp. N-774 are constitutively produced, the NHases of both R. erythropolis strains were inducibly produced by addition of epsilon-caprolactam as an inducer.