Arginine metabolism in wineLactobacillus plantarum: in vitro activities of the enzymes arginine deiminase (ADI) and ornithine transcarbamilase (OTCase)

This work was carried out to determine the activity of enzymes involved in arginine metabolism inLactobacillus plantarum isolated from wine and previously characterised at molecular level. The activity of the enzymes arginine deiminase and ornithine transcarbamylase was determined and citrulline and ornithine formed were analysed by HPLC analysis. Although the enzymatic activity was detected in all the strains analysed, a strong variability was observed between strains.Lactobacillus plantrum strain Lp60 is the strain with more possibilities to accumulate citrulline, precursor of the carcinogenic ethyl-carbamate, as showed by its high arginine deiminase activity and low ornithine transcarbamylase activity.     

Kinetics and metabolic behavior of a composite culture of <Emphasis Type="Italic">Kloeckera apiculata</Emphasis> and <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> wine related strains

The kinetics and metabolic behavior of Kloeckera apiculata mc1 and Saccharomyces cerevisiae mc2 in composite culture was investigated. K. apiculata showed a higher viability through the fermentation; however the maximum cell density of both yeasts decreased. This behavior was not due to ethanol concentration, killer toxins production or competition for assimilable nitrogenous compounds between both yeasts. Despite the consistent production of secondary products by single culture of K. apiculata, an increase of these compounds was not observed in mixed culture. These results contribute to a better understanding of the behavior of non-Saccharomyces yeasts and their potential application in the wine industry.     

Microbial growth and lipolytic activities of moderate thermophilic bacterial strains

Nine bacterial strains grew at 50°C on a mineral medium containing Tween 80 as sole carbon source and three of them produced significant lipolytic activities. The strains showed optimal growth at 50°C and thus, they are moderate thermophiles. Lipolytic activity were maxima at 57–67°C suggesting high thermostability. Lipolytic activity production was promoted by the addition of Tween 80 in culture medium and inhibited by glucose addition. These strains are convenient sources of thermostable lipolytic enzymes for biotechnological applications. © Rapid Science Ltd. 1998     

Differentiation of trophoblast giant cells and their metabolic functions are dependent on peroxisome proliferator-activated receptor beta/delta

Mutation of the nuclear receptor peroxisome proliferator-activated receptor beta/delta (PPARbeta/delta) severely affects placenta development, leading to embryonic death at embryonic day 9.5 (E9.5) to E10.5 of most, but not all, PPARbeta/delta-null mutant embryos. While very little is known at present about the pathway governed by PPARbeta/delta in the developing placenta, this paper demonstrates that the main alteration of the placenta of PPARbeta/delta-null embryos is found in the giant cell layer. PPARbeta/delta activity is in fact essential for the differentiation of the Rcho-1 cells in giant cells, as shown by the severe inhibition of differentiation once PPARbeta/delta is silenced. Conversely, exposure of Rcho-1 cells to a PPARbeta/delta agonist triggers a massive differentiation via increased expression of 3-phosphoinositide-dependent kinase 1 and integrin-linked kinase and subsequent phosphorylation of Akt. The links between PPARbeta/delta activity in giant cells and its role on Akt activity are further strengthened by the remarkable pattern of phospho-Akt expression in vivo at E9.5, specifically in the nucleus of the giant cells. In addition to this phosphatidylinositol 3-kinase/Akt main pathway, PPARbeta/delta also induced giant cell differentiation via increased expression of I-mfa, an inhibitor of Mash-2 activity. Finally, giant cell differentiation at E9.5 is accompanied by a PPARbeta/delta-dependent accumulation of lipid droplets and an increased expression of the adipose differentiation-related protein (also called adipophilin), which may participate to lipid metabolism and/or steroidogenesis. Altogether, this important role of PPARbeta/delta in placenta development and giant cell differentiation should be considered when contemplating the potency of PPARbeta/delta agonist as therapeutic agents of broad application.     

Growth Response and Modifications of Organic Nitrogen Compounds in Pure and Mixed Cultures of Lactic Acid Bacteria from Wine

The interactions between the proteolytic X₂L strain of Oenococcus oeni and the non-proteolytic 12p strain of Pediococcus pentosaceus were assayed. The characteristics of cell growth, protein degradation, and amino acid production of both strains were determined in pure and mixed cultures. O. oeni showed poor cell growth and greater ability in the release of amino acids to the extracellular medium, whereas P. pentosaceus showed a higher yield in cell production with a decrease in the amino acid concentration in the medium. P. pentosaceus especially consumed essential amino acids for growth, and O. oeni released several of the essential amino acids important for growth of P. pentosaceus. In the mixed culture, mutualism was observed. The higher activity of the proteolytic system of O. oeni in mixed culture produced an increase in cell growth and in the amount of essential amino acids released. These findings provide new knowledge about the metabolic interactions between lactic acid bacteria isolated from wine when proteins are degraded in mixed bacterial populations.     

Utilization of amino acids and dipeptides by Lactobacillus plantarum from orange in nutritionally stressed conditions

Aims:  To investigate amino acid and dipeptide utilization by Lactobacillus plantarum N4 isolated from orange peel, in a nutritionally depleted medium based on MRS (Mann, Rogosa, Sharpe).
Methods and Results:  In MRS with 0·1 g l⁻¹ of meat extract and without peptone and yeast extract, growth increased when essential and stimulatory amino acids and nonessential amino acid were added to the medium. Replacement of the essential amino acid, leucine, and the nonessential amino acid, glycine, by leucyl-leucine (Leu-Leu) and/or glycyl-glycine (Gly-Gly) significantly enhanced growth. Essential amino acids were mainly consumed and the dipeptides were almost completely used at the end of growth. Leucine and glycine accumulated internally from the peptides were higher than from the free amino acids. Glucose utilization increased in the media containing dipeptides compared with the medium containing free amino acids.
Conclusions:  In a N-depleted medium, Leu-Leu and/or Gly-Gly were more effective than the respective amino acids in supporting growth of the micro-organism. The more efficient internal accumulation of glycine and especially leucine from dipeptides confirmed the ability of the strain to assimilate mainly complex nitrogen molecules rather than simple ones.
Significance and Impact of the Study:  The ability of Lact. plantarum N4 to efficiently use dipeptides could contribute to spoilage development in the natural medium of the organism, orange juice.     

High pressure reveals structural determinants for globin hexacoordination: Neuroglobin and myoglobin cases

The influence of pressure on the equilibrium between five‐(5c) and six‐coordination (6c) forms in neuroglobin (Ngb) and myoglobin (Mb) has been examined by means of molecular dynamics (MD) simulations at normal and high pressure. The results show that the main effect of high pressure is to reduce the protein mobility without altering the structure in a significant manner. Moreover, our data suggest that the equilibrium between 5c and 6c states in globins is largely controlled by the structure and dynamics of the C‐D region. Finally, in agreement with the available experimental data, the free energy profiles obtained from steered MD for both proteins indicate that high pressure enhances hexacoordination. In Ngb, the shift in equilibrium is mainly related to an increase in the 6c→5c transition barrier, whereas in Mb such a shift is primarily due to a destabilization of the 5c state. Proteins 2009. © 2008 Wiley‐Liss, Inc.     

Structure-based analysis of five novel disease-causing mutations in 21-hydroxylase-deficient patients

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency is the most frequent inborn error of metabolism, and accounts for 90-95% of CAH cases. The affected enzyme, P450C21, is encoded by the CYP21A2 gene, located together with a 98% nucleotide sequence identity CYP21A1P pseudogene, on chromosome 6p21.3. Even though most patients carry CYP21A1P-derived mutations, an increasing number of novel and rare mutations in disease causing alleles were found in the last years. In the present work, we describe five CYP21A2 novel mutations, p.R132C, p.149C, p.M283V, p.E431K and a frameshift g.2511_2512delGG, in four non-classical and one salt wasting patients from Argentina. All novel point mutations are located in CYP21 protein residues that are conserved throughout mammalian species, and none of them were found in control individuals. The putative pathogenic mechanisms of the novel variants were analyzed in silico. A three-dimensional CYP21 structure was generated by homology modeling and the protein design algorithm FoldX was used to calculate changes in stability of CYP21A2 protein. Our analysis revealed changes in protein stability or in the surface charge of the mutant enzymes, which could be related to the clinical manifestation found in patients.     

Epineurial adipocytes are dispensable for Schwann cell myelination

Previous clinical observations and data from mouse models with defects in lipid metabolism suggested that epineurial adipocytes may play a role in peripheral nervous system myelination. We have used adipocyte‐specific Lpin1 knockout mice to characterize the consequences of the presence of impaired epineurial adipocytes on the myelinating peripheral nerve. Our data revealed that the capacity of Schwann cells to establish myelin, and the functional properties of peripheral nerves, were not affected by compromised epineurial adipocytes in adipocyte‐specific Lpin1 knockout mice. To evaluate the possibility that Lpin1‐negative adipocytes are still able to support endoneurial Schwann cells, we also characterized sciatic nerves from mice carrying epiblast‐specific deletion of peroxisome proliferator‐activated receptor gamma, which develop general lipoatrophy. Interestingly, even the complete loss of adipocytes in the epineurium of peroxisome proliferator‐activated receptor gamma knockout mice did not lead to detectable defects in Schwann cell myelination. However, probably as a consequence of their hyperglycemia, these mice have reduced nerve conduction velocity, thus mimicking the phenotype observed under diabetic condition. Together, our data indicate that while adipocytes, as regulators of lipid and glucose homeostasis, play a role in nerve function, their presence in epineurium is not essential for establishment or maintenance of proper myelin.