New Strains of Arthrobacter and Micrococcus Producing Lysine from Hydrocarbon

<正> Following the bioautographic te-chnique, 24 lysine producing microor-ganisms have been isolated from amongthe 263 hydrocarbon utilisers. Morphological, cultural and biochemicalcharacters of two promising isolates,have been studied. One of them iden-tified as Arthrobacter globiformis andthe other as Micrococcus varians, pro-duce 3.4 and 2.6 g lysine per litreof medium.     

Lysine inhibition of Saccharomyces cerevisiae: role of repressible L-lysine ε-aminotransferase

Lysine added to grain mashes under nitrogen-limiting conditions (as in most industrial fermentations) inhibited growth of Saccharomyces cerevisiae. This inhibition was relieved by raising the assimilable nitrogen content. Lysine-induced inhibition is not mediated through accumulation of -oxoadipic acid, an intermediate of lysine metabolism which accumulates by a back up of intermediates in de novo synthesis. Lysine degradation is regulated by the synthesis of L-lysine -aminotransferase, an enzyme that catalyses the first step in one of three possible routes of lysine degradation (not previously reported in S. cerevisiae). Synthesis is repressed under nitrogenlimiting conditions, but derepressed when excess assimilable nitrogen is available. Derepression results in degradation of lysine and decreases inhibitory effects on growth. The toxic compound appears to be lysine itself.The authors are with the Department of Applied Microbiology and Food Science, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 0W0. Canada     

Formation of Lysine from, α, ε-Diaminopimelic Acid Contained in Rumen Bacterial Cell Walls by Rumen Ciliate Protozoa

Cell walls containing α,ε-diaminopimelate-l,7-¹⁴C (DAP) was prepared from Escherichia coli isolated from the rumen. After incubation of ciliates with the cell walls, 22.0% of DAP contained in cell walls of E. coli was converted to lysine and pipecolate. Heat-treated mixed rumen bacteria and heat-treated cell walls of mixed rumen bacteria added to the culture medium of rumen ciliates increased 0.572 and 0.934 μmole/ml of sum of lysine and pipecolate, respectively.

From these results, it is clear that rumen ciliate protozoa can form lysine from DAP contained in the mucopeptide of bacterial cell walls. One of the nutritional significance of inhabitation of ciliates in the rumen was revealed.     

High Lysine and High Tryptophan Transgenic Maize Resulting from the Reduction of Both 19- and 22-kD α-zeins

The major maize seed storage proteins, zeins, are deficient in lysine and tryptophan content, which contribute to the poor nutritional quality of corn. Whether through the identification of mutations or genetic engineering, kernels with reduced levels of zein proteins have been shown to have increased levels of lysine and tryptophan. It has been hypothesized that these increases are due to the reduction of lysine-poor zeins and a pleiotropic increase in the lysine-rich non-zein proteins. By transforming maize with constructs expressing chimeric double-stranded RNA, kernels derived from stable transgenic plants displayed significant declines in the accumulation of both 19- and 22-kD α-zeins, which resulted in higher lysine and tryptophan content than previously reported for kernels with reduced zein levels. The observation that lysine and tryptophan content is correlated with the protein levels measured in transgenic maize kernels is consistent with the hypothesis that a pleiotropic increase in non-zein proteins is contributing to an improved amino acid balance. In addition, a large increase in accumulation of free amino acids, consisting predominantly of asparagine, asparate and glutamate, was observed in the zein reduction kernels.     

Genomic Organization of α-Amylase Gene in High Lysine Opaque-2 Maize

Genomic DNA was isolated from 7-day old etiolated seedlings of normal and high lysine opaque-2 maize and purified by CsCl gradient. Purified DNA was found to be ～48.5 kb in size. Restriction analysis of genomic DNA with EcoRI and HindIII did not reveal any noticeable difference between normal and opaque-2 DNA. Southern blot analysis, using α-amylase probe, showed multiple bands. One of the hybridizing bands (～4 kb) of genomic DNA was more intense in opaque-2 than in normal. This DNA was cloned into pUC 18 plasmid and presence of α-amylase was confirmed by Southern hybridization using α-amylase probe.     

Involvement of meso-α,∊-Diamino-pimelate D-Dehydrogenase in Lysine Biosynthesis in Corynebacterium glutamicum

To characterize aspartyl aminopeptidase from Aspergillus oryzae, the recombinant enzyme was expressed in Escherichia coli. The enzyme cleaves N-terminal acidic amino acids. About 30% activity was retained in 20% NaCl. Digestion of defatted soybean by the enzyme resulted in an increase in the glutamic acid content, suggesting that the enzyme is potentially responsible for the release of glutamic acid in soy sauce mash.     

What Is Characteristic of Fungal Lysine Synthesis Through the α-Aminoadipate Pathway?

Recent finding that a prokaryote synthesizes lysine through the α-aminoadipate pathway demonstrates that the lysine synthesis through the α-aminoadipate pathway is not typical of fungi. However, the fungal lysine biosynthesis is not completely the same as the prokaryotic one. We point out that α-aminoadipate reductase is a key enzyme to the evolution of fungal lysine synthesis. In addition, fungi have two different saccharopine dehydrogenases, which is also characteristic of fungi. Received: 18 February 2000 / Accepted: 19 June 2000     

Predictive QM/MM Modeling of Modulations in Protein–Protein Binding by Lysine Methylation

Lysine methylation is a key regulator of protein–protein binding. The amine group of lysine can accept up to three methyl groups, and experiments show that protein–protein binding free energies are sensitive to the extent of methylation. These sensitivities have been rationalized in terms of chemical and structural features present in the binding pockets of methyllysine binding domains. However, understanding their specific roles requires an energetic analysis. Here we propose a theoretical framework to combine quantum and molecular mechanics methods, and compute the effect of methylation on protein–protein binding free energies. The advantages of this approach are that it derives contributions from all local non-trivial effects of methylation on induction, polarizability and dispersion directly from self-consistent electron densities, and at the same time determines contributions from well-characterized hydration effects using a computationally efficient classical mean field method. Limitations of the approach are discussed, and we note that predicted free energies of fourteen out of the sixteen cases agree with experiment. Critical assessment of these cases leads to the following overarching principles that drive methylation-state recognition by protein domains. Methylation typically reduces the pairwise interaction between proteins. This biases binding toward lower methylated states. Simultaneously, however, methylation also makes it easier to partially dehydrate proteins and place them in protein–protein complexes. This latter effect biases binding in favor of higher methylated states. The overall effect of methylation on protein–protein binding depends ultimately on the balance between these two effects, which is observed to be tuned via several combinations of local features.     

Lysine: Is it worth more?

Lysine, an essential cationic amino acid, has a positively charged R group. The structure of lysine is given as (H₃N⁺-)CH(-COO^-)-CH₂-CH₂-CH₂-CH₂-N⁺H₃.While the anabolic role(s) of the molecule has been in focus for quite a few decades now, its biological properties, e.g. role in cellular proliferation in vitro (both anchorage dependent and anchorage independent) and in vivo, its ability to induce strong inflammatory and immune responses - both humoral and cell mediated, its role in augmented healing of all types of wounds in animal models as well as in human subjects (both acute and chronic), as well as its role in inducing extensive angiogenic responses, have never received reasonable attention so far. In the current brief and indicative review (rather than exhaustive reviews of each area), we intend to bring these biological properties of the molecule to focus while discussing a few other interesting aspects - lysine as a food preservative as well as its possible role(s) in immune therapy. While the areas look extremely divergent, we propose a common denominator in the form of a possible molecular mechanism of action of the molecule in all these diverse situations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Role of Zinc–Lysine on Growth and Chromium Uptake in Rice Plants under Cr Stress

Journal of Plant Growth Regulation - Chromium (Cr) is a very toxic heavy metal present in agricultural soils. Soils contaminated with Cr are the major source of Cr entrance into the food chain. The...     

Arginine and Lysine interactions with �� residues in metalloproteins

Metalloproteins have many different functions in cells such as enzymes; signal transduction, transport and storage proteins. About one third of all proteins require metals to carry out their functions. In the present study we have analyzed the roles played by Arg and Lys (cationic side chains) interactions with π (Phe, Tyr or Trp) residues and their role in the structural stability of metalloproteins. These interactions might play an important role in the global conformational stability in metalloproteins. In spite of its lower natural occurrence (1.76%) the number of Trp residues involved in energetically significant interactions is higher in metalloproteins.     

Alanine Scanning Mutagenesis Identifies an Asparagine–Arginine–Lysine Triad Essential to Assembly of the Shell of the Pdu Microcompartment

Bacterial microcompartments (MCPs) are the simplest organelles known. They function to enhance metabolic pathways by confining several related enzymes inside an all-protein envelope called the shell. In this study, we investigated the factors that govern MCP assembly by performing scanning mutagenesis on the surface residues of PduA, a major shell protein of the MCP used for 1,2-propanediol degradation. Biochemical, genetic, and structural analysis of 20 mutants allowed us to determine that PduA K26, N29, and R79 are crucial residues that stabilize the shell of the 1,2-propanediol MCP. In addition, we identify two PduA mutants (K37A and K55A) that impair MCP function most likely by altering the permeability of its protein shell. These are the first studies to examine the phenotypic effects of shell protein structural mutations in an MCP system. The findings reported here may be applicable to engineering protein containers with improved stability for biotechnology applications.     

Synthetic Antimicrobial Peptides: III—Effect of Cationic Groups of Lysine,Arginine, and Histidine on Antimicrobial Activity of Peptides with a Linear Type of Amphipathicity

Russian Journal of Bioorganic Chemistry - We have studied the antimicrobial and hemolytic activity of synthetic antimicrobial peptides (SAMPs), i.e., Arg9Phe2 (P1-Arg), Lys9Phe2 (P2-Lys), and...     

The Different Inhibition Mechanisms of OXA-1 and OXA-24 β-Lactamases Are Determined by the Stability of Active Site Carboxylated Lysine

The catalytic efficiency of class D β-lactamases depends critically on an unusual carboxylated lysine as the general base residue for both the acylation and deacylation steps of the enzyme. Microbiological and biochemical studies on the class D β-lactamases OXA-1 and OXA-24 showed that the two enzymes behave differently when reacting with two 6-methylidene penems (penem 1 and penem 3): the penems are good inhibitors of OXA-1 but act more like substrates for OXA-24. UV difference and Raman spectroscopy revealed that the respective reaction mechanisms are different. The penems form an unusual intermediate, a 1,4-thiazepine derivative in OXA-1, and undergo deacylation followed by the decarboxylation of Lys-70, rendering OXA-1 inactive. This inactivation could not be reversed by the addition of 100 mm NaHCO₃. In OXA-24, under mild conditions (enzyme:inhibitor = 1:4), only hydrolyzed products were detected, and the enzyme remained active. However, under harsh conditions (enzyme:inhibitor = 1:2000), OXA-24 was inhibited via decarboxylation of Lys-84; however, the enzyme could be reactivated by the addition of 100 mm NaHCO₃. We conclude that OXA-24 not only decarboxylates with difficulty but also recarboxylates with ease; in contrast, OXA-1 decarboxylates easily but recarboxylates with difficulty. Structural analysis of the active site indicates that a crystallographic water molecule may play an important role in carboxylation in OXA-24 (an analogous water molecule is not found in OXA-1), supporting the suggestion that a water molecule in the active site of OXA-24 can lower the energy barrier for carboxylation significantly.     

Production of steviol from steviol glucosides using β-glycosidase from Sulfolobus solfataricus

Steviol is a diterpene isolated from the plant Stevia rebaudiana that has a potential role as an antihyperglycemic agent by stimulating insulin secretion from pancreatic beta cells and also has significant potential to diminish the renal clearance of anionic drugs and their metabolites. In this study, the lacS gene, which encodes a thermostable β-glycosidase (SSbgly) enzyme from the extremely thermoacidophillic archaeon Sulfolobus solfataricus, was cloned and expressed in E. coli Rossetta BL21(DE3)pLyS using lactose as an inducer. Through fermentation, SSbgly was expressed as a 61 kDa protein with activity of 24.3 U/mg and the OD₆₀₀ of 23 was reached after 18 h induction with 10 mM lactose. Purified protein was obtained by Ni-Sepharose chromatography with a yield of 92.3%. SSbgly hydrolyzed steviol glycosides to produce steviol with a yield of 99.2%. The optimum conditions for steviol production were 50 U/ml SSbgly and 90 mg/ml Ste at 75 °C as determined by the response surface method.     

Comparison of the Functional Activities of Xanthine Oxidases Isolated from Microorganisms and from Cow’s Milk

The characteristics of the formation of the superoxide radical anion (\(\rm{O}_2^{\bullet-}\)) and hydrogen peroxide by xanthine oxidases isolated from microorganisms and from cow’s milk were investigated. The increase in pH led to an increase in the rate of xanthine oxidation with oxygen by both xanthine oxidases. The functioning of xanthine oxidase from milk along with the two-electron reduction of O₂ to H₂O₂ carries through the one-electron reduction of O₂ to \(\rm{O}_2^{\bullet-}\), and the rate and the fraction of generation of \(\rm{O}_2^{\bullet-}\) increased with increasing pH. Under operation of the microbial xanthine oxidase, the \(\rm{O}_2^{\bullet-}\) radical was not detected in the medium. The results suggest a difference in the operation of active centers of enzyme from different sources.