Chemically assisted microbial production of succinic acid by the yeast <Emphasis Type="Italic">Yarrowia lipolytica</Emphasis> grown on ethanol

A new two-step process of production of succinic acid (SA) has been developed, which includes the microbial synthesis of alpha-ketoglutaric acid by the yeast Yarrowia lipolytica (step 1) and subsequent oxidation of the acid by hydrogen peroxide to SA (step 2). The maximum concentration of SA and its yield were found to be 63.4 g l⁻¹ and 58% of the ethanol consumed, respectively. The purity of the SA isolated from the culture liquid filtrate reached 100%. The yield of SA was as high as 82% of its amount in the culture liquid filtrate. The quality of the SA produced by the invented method meets the biochemical grade definitions, as is evident from the respiratory and other relevant parameters of rat liver mitochondria upon the oxidation of this SA.     

Effect of hydrogen peroxide on morphological characteristics and resistance of wheat calluses to <Emphasis Type="Italic">T. caries</Emphasis> Tul.

We studied the effect of hydrogen peroxide on morphological characteristics and resistance of common wheat calluses ( Triticum aestivum L.) to Tilletia caries Tul. The induction of the defense response and morphogenesis in calluses depended on H₂O₂ concentration. A correlation was revealed between the elevated concentration of hydrogen peroxide in wheat calluses and high activity of oxalate oxidase in the cell wall. Administration of H₂O₂ into the callus culture medium was followed by rhizogenesis, induced the formation of dense regions, and inhibited fungal growth on calluses. Hydrogen peroxide at high concentrations was less potent in inhibiting the growth of fungi. A relationship was found between oxalate oxidase activity, H₂O₂ concentration, and morphogenetic and defense responses of calluses induced by exogenous hydrogen peroxide. These data suggest that the induction of H₂O₂ generation is one of the approaches to increase callus resistance.     

Changes in the composition and content of lipids in the leaves of radish plants of different magnetic orientation induced by weak permanent magnetic field

The effect of weak permanent horizontal magnetic field (PMF) with the intensity of 403 A/m on the composition and content of polar and neutral lipids and their constituent FAs was investigated in the leaves of radish plants (Raphanus sativus L., var. radicula D.C.), cv. Rozovo-krasnyi s belym konchikom, which belong to two major types of magnetic orientation (TMO): North-South (NS) and West-East (WE), with the planes of the root grooves oriented along and across the magnetic meridian, respectively. In spring, PMF reduced the level of total lipids in the NS plants and elevated it in the WE plants; in autumn, the content of total lipids in the NS plants increased in the NS plants and decreased in the WE plants. In spring, the ratio between phospholipids and sterols, which indirectly points to enhanced fluidity of membrane lipid bilayer, increased in the plants of both TMOs, while in autumn, it increased only in the NS plants. In the control plants, the relative content of unsaturated FAs, including linolenic and linoleic acids, was greater in the WE plants than in the NS plants. PMF elevated the content of FAs in the leaves of the NS plants and did not affect their level in the WE plants. It was concluded that weak horizontal PMF differently (and sometimes oppositely) affected the content of lipids in the leaves of the NS and WE radish plants, apparently due to their different sensitivity to the effect of the magnetic field associated with their physiological status.     

Endonuclease from Proteus mirabilis

Two isoforms of nuclease displaying DNase and RNase activities were found in the culture liquid and periplasm of Proteus mirabilis. The enzyme was isolated from the periplasm and then purified to a functionally homogeneous state. The nuclease was equally potent in cleaving denatured and native DNAs by the endonuclease mechanism and was designated Pm endonuclease. The endonuclease was shown to be a temperature-dependent enzyme with a pH optimum of 10.4–10.6, requiring the presence of bivalent metal ions and inhibited by citrate and ethylenediaminetetraacetate.     

Molecular insights into protein synthesis with proline residues

Proline is an amino acid with a unique cyclic structure that facilitates the folding of many proteins, but also impedes the rate of peptide bond formation by the ribosome. As a ribosome substrate, proline reacts markedly slower when compared with other amino acids both as a donor and as an acceptor of the nascent peptide. Furthermore, synthesis of peptides with consecutive proline residues triggers ribosome stalling. Here, we report crystal structures of the eukaryotic ribosome bound to analogs of mono‐ and diprolyl‐tRNAs. These structures provide a high‐resolution insight into unique properties of proline as a ribosome substrate. They show that the cyclic structure of proline residue prevents proline positioning in the amino acid binding pocket and affects the nascent peptide chain position in the ribosomal peptide exit tunnel. These observations extend current knowledge of the protein synthesis mechanism. They also revise an old dogma that amino acids bind the ribosomal active site in a uniform way by showing that proline has a binding mode distinct from other amino acids.     

Template-free ribosomal synthesis of polypeptides from aminoacyl-tRNA. Polyphenylalanine synthesis from phenylalanyl-tRNALys

Misacylated phenylalanyl-tRNALys, just as lysyl-tRNALys, but not phenylalanyl-tRNAPhe, have been shown to serve as substrates for ribosomal synthesis of polypeptides (polyphenylalanine and polylysine, respectively) in the absence of a template polynucleotide (poly(A)). The conclusion was made that it is the structure of tRNA that determines the ability of the aminoacyl-tRNALys to participate in peptide elongation on ribosomes without codon-anticodon interactions.     

Biosynthesis of endochitinase of Serratia marcescens.

The growth of a mutant strain of Serratia marcescens with high chitinase activity and the biosynthesis of endochitinase by this strain were investigated. The study was carried out using semisynthetic culture medium without inducers and culture medium containing colloidal chitin as a sole nitrogen and carbon source, with and without mitomycin C. The mutant strain, unlike the native one, was shown to produce endochitinase and to secrete the enzyme into the medium during the growth on culture medium without the inducers, chitin and mitomycin C. During growth on the medium with chitin the mutant strain differed from the native one with a short lag-phase of growth, the early appearance of endochitinase in the culture liquid and a high level of endochitinase activity. The difference between the strains disappeared after the addition of mitomycin C, an inducer of the cell SOS-response, to the culture medium containing chitin. Specific endochitinase activity of S. marcescens mutant strain grown on various culture media had two maxima, namely at the beginning and at the end of the stationary phase. Mitomycin C increased the specific activity in a second peak of endochitinase activity during the growth of the mutant strain.     

The activity of peroxidase in various cell fractions of wheat plants infected with Septoria nodorum berk.

The activities of peroxidase isoforms and hydrogen peroxide content in leaf cuttings of wheat (Triticum aestivum L., cv. Diamant) resistant to Septoria blotch were studied during aging and following the infection with Septoria nodorum Berk. The differential activation of peroxidase isoforms was regulated by hydrogen peroxide level in the tissue. At early stages of fungus development in plant tissues, the decrease in the activities of soluble, membrane and ion-bound fractions of peroxidase elevated the level of hydrogen peroxide in infected tissues and rapidly activated peroxidase isoforms in infected tissues as compared to the aging ones even before disease symptoms appeared. The anionic peroxidases, which were first to respond to the pathogen, seem to stand for wheat resistance to fungal infections and the protection of leaf tissues from oxidative stress.