Degradation of Bacillus subtilis glutamine phosphoribosylpyrophosphate amidotransferase in vivo

Maternal yeast-based nucleotide supplementation decreased stillbirth by regulating nutrient metabolism

BACKGROUND

As an enzymatic product of yeast, yeast-based nucleotide (YN) is rich in nucleotides. To test the effects of maternal dietary supplementation with YN during late pregnancy on placental nutrient transport and nutrient metabolism in neonatal piglets, 64 pregnant sows (day 85 ± 3) were assigned into two groups: (i) control (CON) and (ii) treatment (YN; 4 g kg^-1 ). Blood, placenta and liver samples of neonates during delivery were collected.

RESULTS

The results showed that maternal YN supplementation decreased stillbirth rate and intra-uterine growth restriction rate (P < 0.05). In addition, maternal YN supplementation increased total serum protein, albumin and total cholesterol (P < 0.05). Furthermore, in neonatal piglets in the YN group, both serum amino acidand nucleotide profiles were affected, as well as liver amino acid, and fatty acid profiles were regulated (P < 0.05). Moreover, maternal YN supplementation increased liver mRNA expression of SLC28A3, SLC29A1, SLC29A2, PC, PCK1, FBP1, SREBP1c, HSL and CYP7a1 of neonatal piglets (P < 0.05). Meanwhile, there was a decrease in placental gene expression of EAAT2, EAAT3, LAT1 and PAT1, as well as lower protein expression of peroxisome proliferator-activated receptor (PPAR)γ, AKT, phosphorylated-AKT, phosphorylated-mammalian target of rapamycin (mTOR) and Raptor, in the YN group (P < 0.05).

CONCLUSION

Taken together, these results indicate that maternal YN supplementation regulates placental nutrient transport by regulating the mTOR complex 1-PPAR pathway, and affects the liver metabolism of nucleotides, amino acids and fatty acids in neonatal piglets, thereby improving the reproductive performance of sow to a certain extent. © 2020 Society of Chemical Industry.

A mathematical model for examining growth and sporulation processes of Bacillus subtilis

A mathematical model for the growth process of the bacterium Bacillus subtilis is described. The model is a highly structured one. The driving motivation for development of the model and explicit accounting of major interactions of metabolic networks in the model is related to our eventual goal that the model will be used in the analysis of complex biological patterns. Bacillus subtilis was chosen in our study due to the interesting sporulation process that these cells undergo in response to adverse environmental conditions including nutrient limitation. Sporulation process in B. subtilis represents a primordial prototype of cellular differentiation in higher cellular systems. Thus a model for the B. subtilis growth process should prove extremely useful for understanding questions of developmental biology. The model is capable of simulating the transition between the exponential and stationary phase of growth in a batch culture. Since during the transition period the growth process and the metabolism become decoupled and many transient processes are taking place, such predictions are a severe test for the validity of any model. A strategy to examine the leading hypothesis on B. subtills sporulation implementing GTP as a component which signals sporulation initiation is described.

Alanine dehydrogenase (ald) is required for normal sporulation in Bacillus subtilis

The ski22::Tn917lac insertion mutation in Bacillus subtilis was isolated in a screen for mutations that cause a defect in sporulation but are suppressed by the presence or overexpression of the histidine protein kinase encoded by kinA (spoIIJ). The ski22::Tn917lac insertion mutation was in ald, the gene encoding alanine dehydrogenase. Alanine dehydrogenase catalyzes the deamination of alanine to pyruvate and ammonia and is needed for growth when alanine is the sole carbon or nitrogen source. The sporulation defect caused by null mutations in ald was partly relieved by the addition of pyruvate at a high concentration, indicating that the normal role of alanine dehydrogenase in sporulation might be to generate pyruvate to provide an energy source for sporulation. The spoVN::Tn917 mutation was also found to be an allele of ald. Transcription of ald was induced very early during sporulation and by the addition of exogenous alanine during growth. Expression of ald was normal in all of the regulatory mutants tested, including spo0A, spo0K, comA, sigB, and sigD mutants. The only gene in which mutations affected expression of ald was ald itself. This regulation is probably related to the metabolism of alanine.

The degA gene product accelerates degradation of Bacillus subtilis phosphoribosylpyrophosphate amidotransferase in Escherichia coli

A search for genes involved in the inactivation and degradation of enzymes in sporulating Bacillus subtilis led to identification of the B. subtilis degA gene, whose product stimulates degradation of B. subtilis glutamine phosphoribosylpyrophosphate amidotransferase in Escherichia coli cells. degA encodes a 36.7-kDa protein that has sequence similarity to several E. coli and B. subtilis regulatory proteins of the LacI class. B. subtilis degA::cat insertional inactivation mutants had no detectable defect in the inactivation or degradation of phosphoribosylpyrophosphate amidotransferase in glucose- or lysine-starved B. subtilis cells, however. We suggest that degA encodes either a novel protease or, more likely, a gene that stimulates production of such a protease.

Energy and calcium ion dependence of proteolysis during sporulation of Bacillus subtilis cells

Bacterial cells degrade intracellular proteins at elevated rates during starvation and can selectively degrade proteins by energy-dependent processes. Sporulating bacteria can degrade protein with apparent first-order rate constants of over 0.20 h-1. We have shown, with an optimized [14C]leucine-labeling and chasing procedure, in a chemically defined sporulation medium, that intracellular protein degradation in sporulating cells of Bacillus subtilis 168 (trpC2) is apparently energy dependent. Sodium arsenate, sodium azide, carbonyl cyanide m-chlorophenylhydrozone, and N,N'-dicyclohexylcarbodiimide, at levels which did not induce appreciable lysis (less than or equal to 10%) over 10-h periods of sporulation, inhibited intracellular proteolysis by 13 to 93%. Exponentially growing cells acquired arsenate resistance. In contrast to earlier reports, we found that chloramphenicol (100 micrograms/ml) strongly inhibited proteolysis (68%) even when added 6 h into the sporulation process. Restricting the calcium ion concentration (less than 2 microM) in the medium had no effect on rates or extent of vegetative growth, strongly inhibited sporulation (98%), and inhibited rates of proteolysis by 60% or more. Inhibitors of energy metabolism, at the same levels which inhibited proteolysis, did not affect the rate or degree of uptake of Ca2+ by cells, which suggested that the Ca2+ and metabolic energy requirements of proteolysis were independent. Restricting the Ca2+ concentration in the medium reduced by threefold the specific activity in cells of the major intracellular serine proteinase after 12 h of sporulation. Finally, cells of a mutant of B. subtilis bearing an insertionally inactivated gene for the Ca2(+)-dependent intracellular proteinase-1 degraded protein in chemically defined sporulation medium at a rate indistinguishable from that of the wild-type cells for periods of 8 h.

Hyperoxidant states cause microbial cell differentiation by cell isolation from dioxygen

A general theory giving an explanation of microbial cell differentiation is presented. Based on experimental results, an unstable hyperoxidant state is postulated to trigger differentiation. Simple rules, involving the reduction of dioxygen and the isolation from dioxygen by diverse mechanisms, are proposed to govern transitions between the growth state and the differentiated states. With this view, common features of microbial differentiation processes, dimorphic growth, cell differentiation in dioxygen evolving phototrophs and in anaerobes are analyzed. The theory could have implications for understanding cell differentiation in higher organisms.

Protein turnover and proteolysis during sporulation of Bacillus subtilis

A two-dimensional electrophoretic method was used to show that protein degradation occurs immediately after the end of exponential growth but that its occurrence is masked in the usual assay methods for a 2-h period and that degradation is apparently nonselective with respect to protein molar mass or charge. The results suggest that considerable reutilization of internal amino acids may occur during sporulation regardless of the size of the external chase. Finally, the levels of intracellular proteinase activities present even at the end of exponential phase growth, as measured in vitro, are sufficient to account for the maximum rates of protein degradation observed in vivo.

Purification of NADP-dependent glutamate dehydrogenase from Pseudomonas aeruginosa and immunochemical characterization of its in vivo inactivation

The 'high ammonia pathway' enzyme glutamate dehydrogenase (NADP+) is inactivated in cells of Pseudomonas aeruginosa when the stationary phase of growth is reached. Purified glutamate dehydrogenase (NADP+) appeared to be a protein composed of six identical subunits with a molecular weight of 54 000. With antibodies raised against purified enzyme it was found that glutamate dehydrogenase (NADP+) inactivation is accompanied by a parallel decrease in immunologically reactive material. This suggests that glutamate dehydrogenase (NADP+) inactivation is caused or followed by rapid proteolysis.

Degradation of aspartate transcarbamylase in Bacillus subtilis is deficient in rel mutants but is not mediated by guanosine polyphosphates

Degradation of aspartate transcarbamylase in growing and starved Bacillus subtilis was deficient in relA and relC mutants, but these effects were not correlated with differences in the intracellular level of guanosine polyphosphates.

A possible role for oxygen inactivation in the regulation of amidophosphoribosyltransferase activity in mammalian cells

Human and other mammalian forms of ATase, including the Chinese hamster enzyme, are oxygen-sensitive enzymes and human ATase, like the enzyme from B. subtilis, is an iron-sulfur protein. When protein synthesis is inhibited in cultured Chinese hamster cells, ATase activity is lost in an oxygen-dependent reaction. The hypothesis is developed that the sensitivity of ATase to oxygen inactivation controls the rate of degradation of this enzyme in mammalian cells, similar to the mechanism which has been demonstrated for regulation of ATase degradation in B. subtilis.

Degradation of ornithine transcarbamylase in sporulating Bacillus subtilis cells

When Bacillus subtilis cells grew and sporulated on glucose-nutrient broth, ornithine transcarbamylase (OTCase) was synthesized in the early stationary phase and then inactivated. The loss of OTCase activity was much slower in a mutant that was deficient in a major intracellular serine protease (ISP). Immunochemical analysis showed that synthesis of OTCase decreased to a low, but detectable, level during its inactivation and that loss of activity was paralleled by loss of cross-reactive protein. Because the antibodies were capable of detecting denatured and fragmented forms of OTCase, we conclude that inactivation involved or was rapidly followed by degradation in vivo. Native OTCase was not degraded in crude extracts or when purified ISP and OTCase were incubated together under a variety of conditions. Synthesis of OTCase was not shut off normally in the ISP-deficient mutant. When the effects of continued synthesis were minimized, OTCase was degraded only slightly slower in the mutant than in its parent. Thus, the mutant had unanticipated pleiotropic characteristics, and it was unlikely that ISP played a major role in the degradation of OTCase in vivo.

Involvement of the stringent response in degradation of glutamine phosphoribosylpyrophosphate amidotransferase in Bacillus subtilis

Glutamine phosphoribosylpyrophosphate amidotransferase, the first enzyme of purine biosynthesis, has previously been shown to be rapidly inactivated and degraded in Bacillus subtilis cells at the end of growth. The loss of enzyme activity appears to involve the oxidation of an iron-sulfur cluster in the enzyme. The degradation of the inactive enzyme involves some elements of the stringent response because it is inhibited in relA and relC mutants. Intracellular pools of guanosine tetra- and pentaphosphate were measured by an improved extraction procedure in cells that had been manipulated in various ways to induce or inhibit amidotransferase degradation. The results are consistent with the hypothesis that one or both of these nucleotides stimulates the synthesis of a protein involved in degradation. An elevated level of these nucleotides was not required for the continued degradation of amidotransferase once it had begun.