SEARCH · PubMed Health

Results for “AMIDASES”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 703 records · Page 39Linked to original sources

PubMed1997

The pneumococcal cell wall degrading enzymes: a modular design to create new lysins?

Autolysins are enzymes that degrade different bonds in the peptidoglycan and, eventually, cause the lysis and death of the cell. Streptococcus pneumoniae contains a powerful autolytic enzyme that has been characterized as an N-acetylmuramoyl-L-alanine amidase. We have cloned the lytA gene coding for this amidase and studied in depth the genetics and expression of this gene, which represented the first molecular analysis of a bacterial autolysin. Two observations have been fundamental in revealing further knowledge on the lytic systems of pneumococcus: (a) The well-documented dependence of the pneumococcal autolysin on the presence of choline in the cell wall for activity, and (b) the early observation that most pneumococcal phages also required the presence of this amino-alcohol in the growth medium to achieve a successful liberation of the phage progeny. We concluded that choline would serve as an element of strong selective pressure to preserve certain structures of the host and phage lytic enzymes which should lead to sequence homologies. We constructed active chimeras between the lytic enzymes of S. pneumoniae and its bacteriophages using genes that share sequence homology as well as genes that completely lack homologous regions. In this way, we demonstrated that the pneumococcal lytic enzymes are the result of the fusion of two independent functional modules where the carboxy-terminal domain might be responsible for the specific recognition of choline-containing cell walls whereas the active center of these enzymes should be localized in the N-terminal part of the protein. The modular design postulated for the pneumococcal lysins seems to be a widespread model for many types of microbial proteins and the construction of functional chimeric proteins between the lytic enzymes of pneumococcus and those of several gram-positive microorganisms, like Clostridium acetobutylicum or Lactococcus lactis, provided interesting clues on the modular evolution of proteins. The study of several genes coding for the lytic enzymes of temperate phages of pneumococcus also highlighted on some evolutionary relationships between microorganisms. We suggest that lysogenic relationships may represent a common mechanism by which pathogenic organisms like pneumococcus should undergo a rapid adaptation to an evolving environment.

Bacteriolysis↗

PubMed1993

Analysis of Bacillus subtilis 168 prophage-associated lytic enzymes; identification and characterization of CWLA-related prophage proteins.

The CWLA lytic amidase of Bacillus subtilis 168 was purified and antisera raised against the purified protein. No expression of cwlA could be demonstrated under any conditions by the use of the antisera and cwlA::lacZ fusion analysis. Two lytic enzymes of apparent molecular masses 34 and 30 kDa (as measured by renaturing SDS-PAGE) were found to be mitomycin C-inducible, the larger of which corresponds to a protein immunologically related to CWLA. Both of these inducible lysins were found to be encoded by prophage PBSX. Prophage SP beta was shown by renaturing SDS-PAGE to produce a 43 kDa lytic enzyme unrelated immunologically to CWLA. The smaller of the two PBSX enzymes was purified and found to be an N-acetylmuramyl-L-alanine amidase of 32 kDa (as measured by SDS-PAGE and Coomassie blue staining) which cross-reacts only weakly with the anti-CWLA sera. The potential origin of cwlA and its possible relationship to the other phage lytic enzymes are discussed.

Bacillus Phages↗

PubMed1997

Subcellular localization of the major autolysin, ATL and its processed proteins in Staphylococcus aureus.

The Staphylococcus aureus autolysin gene, atl, encodes a unique 138-kDa protein (ATL) with amidase and glucosaminidase domains. ATL has been suggested to undergo proteolytic processing to generate two extracellular peptidoglycan hydrolases, 51-kDa endo-beta-N-acetylglucosaminidase (51-kDa GL) and 62-kDa N-acetylmuramyl-L-alanine amidase (62-kDa AM). To investigate cell-associated bacteriolytic enzymes for atl gene products, proteins were extracted from the cells as follows. The cells were exposed to 3 M LiCl followed by 4% SDS. Thereafter, the cells were disrupted and again extracted with 4% SDS. Whole SDS-stable cell-associated bacteriolytic proteins were extracted without disrupting the cells. Exposure to 3 M LiCl released major 138-, 115-, 85-, 62- and 51-kDa bacteriolytic proteins, and subsequent 4% SDS extraction released major 138- and 115-kDa bacteriolytic proteins. These bacteriolytic proteins were missing in extracts of atl mutant RUSAL2 (S. aureus RN450 atl::Tn551). Immunoblotting studies suggest that these are all atl gene products: the 138-kDa protein is an ATL with a cleaved signal sequence; the 115- and 85-kDa proteins are intermediates; and the 51- and 62-kDa proteins are cell-associated 51-kDa GL and 62-kDa AM, respectively. The trypsin susceptibility of these proteins suggests that they are located outside the cell membrane. Differences in extractability and immunoelectron microscopic studies suggest that atl gene products are associated with cells in two different ways, LiCl extractable and non extractable. We suggest that the 138-kDa ATL undergoes processing through intermediate proteins (115- and 85-kDa proteins) to mature as the active cell cluster-dispersing enzymes 51-kDa GL and 62-kDa AM on the cell surface.

Amino Acid Sequence↗

PubMed2002

Molecular characterization of an atl null mutant of Staphylococcus aureus.

atl is a gene encoding a bifunctional peptidoglycan hydrolase of Staphylococcus aureus. The gene product of atl is a 138 kDa protein that has an amidase domain and a glucosaminidase domain, and undergoes processing to generate two major peptidoglycan hydrolases, a 51 kDa glucosaminidase and a 62 kDa amidase in culture supernatant. An atl null mutant was isolated by allelic replacement and characterized. The mutant grew in clusters and sedimented when grown in broth culture. Analysis of peptidoglycan prepared from the wild type and the mutant revealed that there were no differences in muropeptide composition or in glycan chain length distribution. On the other hand, the atl mutation resulted in pleiotropic effects on cell surface nature. The mutant cells showed complete inhibition of metabolic turnover of cell wall peptidoglycan and revealed a rough outer cell wall surface. The mutation also decreased the amount of protein non-covalently bound to the cell surface and altered the protein profile, but did not affect proteins covalently associated with the cell wall. Lysis of growing cells treated with otherwise lytic concentration of penicillin G was completely inhibited in the mutant, but that of non-growing cells was not affected by the mutation. The atl mutation did not significantly affect the ability of S. aureus to provoke an acute infection when inoculated intraperitoneally in a mouse sepsis model. These results further support the supposition that atl gene products are involved in cell separation, cell wall turnover and penicillin-induced lysis of the cells.

Animals↗

PubMed1992

Studies on the structure and function of the N-terminal domain of the pneumococcal murein hydrolases.

The structures of the choline-dependent pneumococcal murein hydrolases, LYTA amidase and CPL1 lysozyme, and the choline-independent CPL7 lysozyme were analysed by controlled proteolytic digestions. The trypsin cleavage of the CPL1 and CPL7 lysozymes produced two resistant polypeptides, F1 and F7 respectively, corresponding to the N-terminal domain of the enzymes, whereas the amidase LYTA was completely hydrolysed by the protease. Interestingly, the F1 and F7 fragments showed a low, but significant, choline-independent lysozyme activity. Choline reduced the rate of proteolytic hydrolysis of choline-dependent enzymes, suggesting that the C-terminal choline-binding domain adopts a more resistant conformation in the presence of the ligand. On the other hand, the regions encoding the N-terminal domains of the three enzymes have been cloned and expressed in Escherichia coli, showing that these domains adopt an active conformation even in the absence of their C-terminal domains. The lower activity shown by the catalytic domains when compared with that of the complete enzymes suggests that the acquisition of a substrate-binding domain represents a noticeable evolutionary advantage for enzymes that interact with polymeric substrates, allowing them to achieve a higher catalytic efficiency. These results strongly reinforce the hypothesis that the pneumococcal murein hydrolases have been originated by fusion of two structural and functional independent domains, and provide new experimental support to the theory of modular evolution of proteins.

Amidohydrolases↗

PubMed1994

The gene of the N-acetylglucosaminidase, a Bacillus subtilis 168 cell wall hydrolase not involved in vegetative cell autolysis.

lytD, the structural gene of the Bacillus subtilis 168 N-acetylglucosaminidase was localized at 310 degrees, next to the tagABC operon. Sequence analysis revealed a monocistronic operon encoding a 95.6 kDa protein endowed with an export signal, the cleavage of which yields the monomer polypeptide (92.8 kDa) of the dimeric active form of the enzyme. Transcription is initiated at a sigma-D (sigma D)-dependent promoter and ends at a terminator common to lytD and the divergently transcribed tagABC operon. In addition, we report the sequence of the adjacent upstream ORF, transcribed in the same direction as lytD, which shows significant homology to phosphomannose isomerase-encoding genes. Cell separation, motility, autolysis, cell wall turnover and growth were not affected in strains devoid of the N-acetylglucosaminidase. A mutant deficient in the two most abundant autolysins, i.e. the LytC amidase and the glucosaminidase, exhibited the phenotype of the amidase-deficient strains, revealing their non-requirement for growth. This conclusion raises two fundamental questions: how does the cell undo the highly cross-linked peptidoglycan so as to be able to grow, and what is the role of the considerable amount of autolysin normally present? Possible answers to these questions are discussed.

Acetylglucosaminidase↗

PubMed1996

Relationship between phase variation in colony morphology, intrastrain variation in cell wall physiology, and nasopharyngeal colonization by Streptococcus pneumoniae.

Streptococcus pneumoniae undergoes phase variation in colony morphology, which has been implicated as a factor in the pathogenesis of pneumococcal disease. Phenotypic differences between opaque and transparent colony forms correlate with differences in rates of autolysis. This study examined whether differences in autolysis are caused by differences in expression of the major amidase, LytA, or the structure of its peptidoglycan substrate. No significant difference was detected by high-pressure liquid chromatography analysis of stem peptides released after treatment of purified peptidoglycan with amidase. Differences in the rate of digestion of purified cell walls, furthermore, did not correlate with susceptibility to autolysis. Lower levels of autolysis in opaque variants, however, was associated with decreased levels of immunodetectable LytA on colony immunoblots and Western blots (immunoblots). Diminished cell-surface-associated LytA in opaque variants was also demonstrated by whole-cell inhibition enzyme-linked immunosorbent assay. Since transparent variants have been shown both to colonize the nasopharynx more efficiently in an animal model and to express more surface-exposed LytA, it was determined whether LytA contributes to colonization in a neonatal rat model of pneumococcal carriage. Defined mutants in the lytA gene were used to show that there was no significant contribution by LytA to nasopharyngeal colonization in this model. Although the expression of LytA was shown to undergo phase variation in association with colony morphology, lytA mutants are still capable of phenotypic variation in colony morphology, which suggests that other factors are responsible for intrastrain differences which affect colonization.

Animals↗

PubMed2006

Biofilm formation by Streptococcus pneumoniae: role of choline, extracellular DNA, and capsular polysaccharide in microbial accretion.

Streptococcus pneumoniae colonizes the human upper respiratory tract, and this asymptomatic colonization is known to precede pneumococcal disease. In this report, chemically defined and semisynthetic media were used to identify the initial steps of biofilm formation by pneumococcus during growth on abiotic surfaces such as polystyrene or glass. Unencapsulated pneumococci adhered to abiotic surfaces and formed a three-dimensional structure about 25 microm deep, as observed by confocal laser scanning microscopy and low-temperature scanning electron microscopy. Choline residues of cell wall teichoic acids were found to play a fundamental role in pneumococcal biofilm development. The role in biofilm formation of choline-binding proteins, which anchor to the teichoic acids of the cell envelope, was determined using unambiguously characterized mutants. The results showed that LytA amidase, LytC lysozyme, LytB glucosaminidase, CbpA adhesin, PcpA putative adhesin, and PspA (pneumococcal surface protein A) mutants had a decreased capacity to form biofilms, whereas no such reduction was observed in Pce phosphocholinesterase or CbpD putative amidase mutants. Moreover, encapsulated, clinical pneumococcal isolates were impaired in their capacity to form biofilms. In addition, a role for extracellular DNA and proteins in the establishment of S. pneumoniae biofilms was demonstrated. Taken together, these observations provide information on conditions that favor the sessile mode of growth by S. pneumoniae. The experimental approach described here should facilitate the study of bacterial genes that are required for biofilm formation. Those results, in turn, may provide insight into strategies to prevent pneumococcal colonization of its human host.

Amidohydrolases↗

PubMed1997

Localized perforation of the cell wall by a major autolysin: atl gene products and the onset of penicillin-induced lysis of Staphylococcus aureus.

We investigated the cell surface localization of the atl gene products of Staphylococcus aureus exposed to a lytic concentration (4 MIC) of penicillin G (PCG) by means of immunoelectron microscopy using anti-62-kDa N-acetylmuramyl-L-alanine amidase or anti-51-kDa endo-beta-N-acetylglucosaminidase immunoglobulin G. Protein A-gold conjugates reacting with antigen-antibody complex localized at sites of defects of the cell wall at the nascent cross wall. Anti-62-kDa N-acetylmuramyl-L-alanine amidase or anti-51-kDa endo-beta-N-acetylglucosaminidase immunoglobulin G inhibited the decreased turbidity caused by PCG-induced lysis and the formation of defects in the wall. The autolysis-defective mutant, S. aureus RUSAL2 (atl::Tn551), exposed to 4 MIC of PCG resisted autolysis and formation of the wall defect. These results suggest that activation or deregulation of the atl gene products at localized sites where formation of new cross wall was disturbed by PCG causes small defects in the cell wall in situ, eventually leading to general autolysis.

Antibodies↗

PubMed2004

Production of muramic delta-lactam in Bacillus subtilis spore peptidoglycan.

Bacterial spore heat resistance is primarily dependent upon dehydration of the spore cytoplasm, a state that is maintained by the spore peptidoglycan wall, the spore cortex. A peptidoglycan structural modification found uniquely in spores is the formation of muramic delta-lactam. Production of muramic delta-lactam in Bacillus subtilis requires removal of a peptide side chain from the N-acetylmuramic acid residue by a cwlD-encoded muramoyl-L-Alanine amidase. Expression of cwlD takes place in both the mother cell and forespore compartments of sporulating cells, though expression is expected to be required only in the mother cell, from which cortex synthesis derives. Expression of cwlD in the forespore is in a bicistronic message with the upstream gene ybaK. We show that ybaK plays no apparent role in spore peptidoglycan synthesis and that expression of cwlD in the forespore plays no significant role in spore peptidoglycan formation. Peptide cleavage by CwlD is apparently followed by deacetylation of muramic acid and lactam ring formation. The product of pdaA (yfjS), which encodes a putative deacetylase, has recently been shown to also be required for muramic delta-lactam formation. Expression of CwlD in Escherichia coli results in muramoyl L-Alanine amidase activity but no muramic delta-lactam formation. Expression of PdaA alone in E. coli had no effect on E. coli peptidoglycan structure, whereas expression of CwlD and PdaA together resulted in the formation of muramic delta-lactam. CwlD and PdaA are necessary and sufficient for muramic delta-lactam production, and no other B. subtilis gene product is required. PdaA probably carries out both deacetylation and lactam ring formation and requires the product of CwlD activity as a substrate.

Amidohydrolases↗

PubMed2002

Molecular peculiarities of the lytA gene isolated from clinical pneumococcal strains that are bile insoluble.

The autolytic LytA amidase from 12 bile (deoxycholate)-insoluble streptococcal isolates (formerly classified as atypical Streptococcus pneumoniae) showing different antibiotic resistance patterns was studied. These atypical strains, which autolyze at the end of the stationary phase of growth, contain highly divergent lytA alleles (pairwise evolutionary distances of about 20%) compared to the lytA alleles of typical pneumococci. The atypical LytA amidases exhibit a peculiar deletion of two amino acids responsible for cell wall anchoring in the carboxy-terminal domain and have a reduced specific activity. These enzymes were inhibited by 1% deoxycholate but were activated by 1% Triton X-100, a detergent that could be used as an alternative diagnostic test for this kind of strain. Preparation of functional chimeric enzymes, PCR mutagenesis, and gene replacements demonstrated that the characteristic bile insolubility of these atypical strains was due to their peculiar carboxy-terminal domain and that the 2-amino-acid deletion was responsible for the inhibitory effect of deoxycholate. However, the deletion alone did not affect the specific activity of LytA. A detailed characterization of the genes encoding the 16S rRNA and SodA together with multilocus sequence typing indicated that the strains studied here are not a single clone and, although they cannot be strictly classified as typical pneumococci, they represent a quite diverse pool of organisms closely related to S. pneumoniae. The clinical importance of these findings is underlined by the role of the lytA gene in shaping the course of pneumococcal diseases. This study can also contribute to solving diagnostic problems and to understanding the evolution and pathogenic potential of species of the Streptococcus mitis group.

Alleles↗

PubMed1987

Structure of the peptide network of pneumococcal peptidoglycan.

The peptide network of Streptococcus pneumoniae cell walls was solubilized using the pneumococcal autolytic amidase (N-acetylmuramoyl-L-alanine amidase, EC 3.5.1.28). The peptide material was fractionated into size classes by gel filtration followed by reverse-phase high-performance liquid chromatography which resolved the peptide population into over 40 fractions. About 40% of the lysines present participate in cross-links between stem peptides. The main components (3 monomers, 5 dimers, and 2 trimers), accounting for 77% of all the wall peptides, were purified. Their structures were determined using a combination of amino acid and end-group analysis, mass spectrometry, and gas-phase sequencing. Two different types of cross-links between stem peptides were found. In the most abundant type there is an alanylserine cross-bridge between the alanine in position 4 of the donor stem peptide and the lysine at position 3 of the acceptor peptide, as in type A3 peptidoglycan. In the second type of cross-link there is no intervening cross-bridge, as in the type A1 peptidoglycan of Gram-negative bacteria. The data indicate that pneumococcal peptidoglycan has a structural complexity comparable to that recently shown in some Gram-negative species.

Cell Wall↗

PubMedDate not supplied

A simple, clinical assay to evaluate the acrosin activity of human spermatozoa.

Acrosin, a sperm-specific acrosomal proteinase, has an essential role in the fertilization process. Low levels of acrosin appear to be associated with subfertility and infertility, and the acrosin activity of spermatozoa may potentially be a useful indicator of semen quality. The standard acrosin tests employed by research laboratories are too complicated and/or time consuming for clinical use; therefore, a simple assay has been developed to assess total acrosin activity (acrosin and activatable proacrosin). To perform the test, liquefied semen is centrifuged over Ficoll, the washed sperm pellet is suspended in a detergent (Triton X-100)-substrate (N-alpha-benzoyl-DL-arginine p-nitroanilide) buffer, pH. 8.0, and the amidase activity is determined spectrophotometrically after a 3-hour incubation period. Amidase activity can be inhibited with benzamidine, indicating that the activity is primarily or entirely due to acrosin. The absence of detergent in the incubation medium results in greatly reduced activity. The assay is repeatable, linear with increasing sperm concentration, sensitive to a lower limit of 2 x 10(6) spermatozoa, and the results correspond to those obtained with a standard acrosin extraction and assay technique. Storage of ejaculates at 3 to 6 C or at 22 to 24 C for 24 hours does not affect the acrosin activity significantly but much higher temperatures can cause a loss of activity. Freezing ejaculates results in a large decrease in sperm acrosin activity. Leukocytes show minimal activity in the assay. Sperm populations prepared by a swim-up procedure average approximately a 2-fold higher acrosin activity than the original ejaculates. Preliminary experiments indicate that the average sperm acrosin activity of ejaculates whose spermatozoa successfully fertilize human eggs in vitro is significantly higher than those that do not fertilize eggs.

Acrosin↗

PubMed1994

Active site structure and stability of the thiol protease papain studied by electron paramagnetic resonance employing a methanethiosulfonate spin label.

The electron paramagnetic resonance (EPR) spin labeling technique has been employed to study the properties and conformation of the thiol protease papain in solution, using (1-oxyl-2,2,5,5-tetramethyl-delta 3-pyrroline-3-methyl) methanethiosulfonate (MTS) as the spin label. The measurements of papain's amidase activity corroborate the EPR results. The major findings are: (i) the motion of the MTS spin label is very sensitive to the active site conformation of papain, which may reflect the location of the pyrroline ring of the spin label near the narrow portion of the active site cleft of papain, and thus there may be intimate interactions between the spin label and its environment; (ii) the active site cleft of papain may have a more open structure at intermediate pH (pH 4.2 to 8.0) than at higher (pH > 8.0) or lower (pH < 4.2) pH, which is consistent with the bell-shape pH curve of the enzyme's amidase activity with the optimum pH at pH 7.00; and (iii) the motion of spin label at the active site of free papain in solution becomes slower upon addition of a denaturant (urea or guanidine hydrochloride), suggesting that the denatured enzyme may have a more closed active site cleft. Urea is more effective than guanidine hydrochloride in denaturing papain at low concentration. However, both urea and guanidine hydrochloride can completely inactivate papain at high concentrations. When an appropriate spin label is selected to label the active site of papain (such as MTS spin label), the EPR spin labeling technique may offer additional insight into the conformation of papain over that obtained by optical methods. These results are discussed in terms of possible studies of biofunctional membranes, opaque assemblies in which a biological molecule is attached to a polymeric membrane.

Binding Sites↗

PubMed1991

Metabolism of acrylonitrile by Klebsiella pneumoniae.

A gram-negative rod-shaped bacterium capable of utilizing acrylonitrile as the sole source of nitrogen was isolated from industrial sewage and identified as Klebsiella pneumoniae. The isolate was capable of utilizing aliphatic nitriles containing 1 to 5 carbon atoms or benzonitrile as the sole source of nitrogen and either acetamide or propionamide as the sole source of both carbon and nitrogen. Gas chromatographic and mass spectral analyses of culture filtrates indicated that K. pneumoniae was capable of hydrolyzing 6.15 mmol of acrylonitrile to 5.15 mmol of acrylamide within 24 h. The acrylamide was hydrolyzed to 1.0 mmol of acrylic acid within 72 h. Another metabolite of acrylonitrile metabolism was ammonia, which reached a maximum concentration of 3.69 mM within 48 h. Nitrile hydratase and amidase, the two hydrolytic enzymes responsible for the sequential metabolism of nitrile compounds, were induced by acrylonitrile. The optimum temperature for nitrile hydratase activity was 55 degrees C and that for amidase was 40 degrees C; both enzymes had pH optima of 8.0.

Acrylonitrile↗

PubMed1992

Genetic structure, isolation and characterization of a Bacillus licheniformis cell wall hydrolase.

A DNA fragment containing the gene for a cell wall hydrolase of Bacillus licheniformis was cloned into Escherichia coli. Sequencing of the fragment showed the presence of an open reading frame which encodes a polypeptide of 253 amino acids with a molecular mass of 27,513. The gene was designated as cwlM, for cell wall lysis. The deduced amino acid sequence indicated that there is a repeated sequence consisting of 33 amino acid residues in the C-terminal region. Deletion of the C-terminal region did not lead to any loss of cell wall lytic activity. The gene product purified from E. coli cells harboring a cwlM-bearing plasmid exhibited a M(r) value of 29 kDa on SDS-polyacrylamide gels, and characterization of the specific substrate bond cleaved by CWLM indicated that the enzyme is an N-acetylmuramoyl-L-alanine amidase (EC 3.5.1.28). The enzyme hydrolyzed the cell wall of Micrococcus luteus more efficiently than those of B. licheniformis and B. subtilis, but the truncated CWLM (lacking the C-terminal region) had lost this preference. CWLM prepared from B. subtilis cells harboring a plasmid containing cwlM had a similar M(r) value to that from E. coli. Amino acid sequence homologies between CWLM and other amidases, and their protein structures are discussed.

Amino Acid Sequence↗

PubMed1986

Isolation, characterization and physiological properties of an autolytic-deficient mutant of Streptococcus pneumoniae.

A spontaneous mutation in the gene lyt encoding the pneumococcal autolysin has been characterized. This mutation, named lyt-32, which behaves as a high-efficiency marker in pneumococcal transformation, is a single base pair GC deletion causing the appearance of two consecutive termination codons in the amino terminal part of the sequence of the autolysin gene. The mutant lyt gene did not code for a polypeptide of relative molecular mass corresponding to the pneumococcal E form amidase in Escherichia coli maxicells. Pneumococcal cells containing the lyt-32 mutation (M32) were fully transformable, multiplied at a normal growth rate forming small chains and showed a tolerant response when treated with beta-lactam antibiotics. Strain M32 represents the first example of a mutant of Streptococcus pneumoniae completely lacking amidase as a consequence of an alteration in the structural gene coding for the pneumococcal autolysin.

Base Sequence↗

PubMed1986

Regulation of nitrile-hydratase synthesis in a Brevibacterium species.

The regulation of nitrile-hydratase biosynthese was studied in Brevibacterium sp R 312. Enzyme biosynthesis was not influenced by any carbon and nitrogen source used in the growth medium. It was, however, repressed by amide and amide analogues. Acetamide repressed nitrile-hydratase biosynthesis and induced the wide-spectrum amidase. Therefore, it appeared reasonable to hypothesize a single repressor gene for the nitrile-hydratase/wide-spectrum amidase system.

Acetamides↗