Selective alterations in hepatic enzyme response after reduction of nuclear triiodothyronine receptor sites by partial hepatectomy and starvation.

Barley embryo 5S rRNA hybridizes efficiently with barley embryo 18S rRNA but not with 26S rRNA. Mouse sarcoma 5S rRNA also selectively hybridizes, to a smaller extent, with mouse sarcoma 18S rRNA. The barley embryo 5S–18S rRNA complex has a sharp melting profile and a “Tm” of $\text{ca}$. 59° in 0.1 $\text{M}$ NaCl. The mouse sarcoma 5S–18S rRNA complex has a broader transition breadth and a “Tm” of $\text{ca}$ 52°. The conditions used for hybridization lead to very specific reconstitution of the “natural” complex between 5.8S and 26S–28S rRNA since both the $\text{in}\text{vivo}\text{and}\text{in}\text{vitro}$ complexes between 5.8S and 26S–28S rRNA from barley embryos and mouse sarcoma have equally sharp melting profiles and a “Tm” of $\text{ca}$. 52° in 0.1 $\text{M}$ NaCl.     

Succinate production in dual-phase Escherichia coli fermentations depends on the time of transition from aerobic to anaerobic conditions

We examined succinic acid production in Escherichia coli AFP111 using dual-phase fermentations, which comprise an initial aerobic growth phase followed by an anaerobic production phase. AFP111 has mutations in the pfl, ldhA, and ptsG genes, and we additionally transformed this strain with the pyc gene (AFP111/pTrc99A-pyc) to provide metabolic flexibility at the pyruvate node. Aerobic fermentations with these two strains were completed to catalog physiological states during aerobic growth that might influence succinate generation in the anaerobic phase. Activities of six key enzymes were also determined for these aerobic fermentations. From these results, six transition times based on physiological states were selected for studying dual-phase fermentations. The final succinate yield and productivity depend greatly on the physiological state of the cells at the time of transition. Using the best transition time, fermentations achieved a final succinic acid concentration of 99.2 g/l with an overall yield of 110% and productivity of 1.3 g/l h. Journal of Industrial Microbiology & Biotechnology (2002) 28, 325–332 DOI: 10.1038/sj/jim/7000250 Received 01 October 2001/ Accepted in revised form 12 March 2002     

Phenetic groupings in bees of the tribe bombini based on the enzyme α-glycerophosphate dehydrogenase

GDH isozyme patterns from thoracic muscle of 21 species of Bombus and 4 species of Psithyrus are each characterized by at least 8 bands arranged in 3 isozyme groups. Four distinctive pattern types were found, one for the species of Psithyrus and three among the Bombus species analyzed. Phenetic groupings of the 25 species are presented. Tissue specific GDH patterns are reported. No quantitative or qualitative differences in GDH patterns from thoracic extracts were associated with caste or age. The enzymes appear to be controlled by four non-allelic genes.     

Effect of methotrexate (MTX) on NAD(P)+ dehydrogenases of HeLa cells: malic enzyme, 2-oxoglutarate and isocitrate dehydrogenases

The effects of methotrexate (MTX) on oxygen uptake by permeabilized HeLa cells were evaluated. MTX did not inhibit state III respiration when the oxidizable substrate was succinate, but when the substrates were 2-oxoglutarate or isocitrate the respiration decreased about 50 per cent at 1·0 mM concentration of the drug. This effect was explained by inhibition of 2-oxoglutarate and isocitrate dehydrogenases by MTX. No effect was observed on succinate dehydrogenase. An evaluation of the effects of MTX on malic enzyme activity as measured by pyruvate plus lactate production in intact cells supplied with malate showed a decrease of about 40 per cent in metabolite production using 0·4 mM MTX. HeLa cell malic enzyme, as observed for other tumour cells, is compartmentalized in mitochondria and cytosol, and is another example of a dehydrogenase inhibited by MTX. © 1997 John Wiley & Sons, Ltd.     

Malic enzyme in the leaves of Bryophyllum daigremontianum

Malic enzyme (E.C. 1.1.1.40) was purified 125-fold from the leaves of Bryophyllum daigremontianum, and shown to be activated allosterically by its substrate.     

The effect of NADP-dependent malic enzyme expression and anaerobic C4 metabolism in Escherichia coli compared with other anaplerotic enzymes

AIMS: To understand the modification of C4-metabolism under anaerobic glycolysis condition by overexpressing anaplerotic enzymes, which mediating carboxylation of C3 into C4 metabolites, in Escherichia coli. METHODS AND RESULTS: Anaplerotic NADP-dependent malic enzyme (MaeB), as well as the other anaplerotic enzymes, including phosphoenolpyruvate carboxylase (Ppc), phosphoenolpyruvate carboxykinase (Pck) and NAD-dependent malic enzyme (MaeA), were artificially expressed and their C4 metabolism was compared in E. coli. Increasing MaeB expression enhanced the production of C4 metabolites by 2.4 times compared to the wild-type strain in anaerobic glucose medium with bicarbonate supplementation. In MaeB expression, C4 metabolism by supplementing 10 g l(-1) of NaHCO(3) was three times than that by no supplementation, which showed the greatest response to increased CO(2) availability among the tested anaplerotic enzyme expressions. CONCLUSIONS: The higher C4 metabolism was achieved in E. coli expressing increased levels of the NADPH-dependent MaeB. The greatest increase in the C4 metabolite ratio compared to the other tested enzymes were also found in E. coli with enhanced MaeB expression as CO(2) availability increased. SIGNIFICANCE AND IMPACT OF THE STUDY: The higher C4 metabolites and related biomolecule productions can be accomplished by MaeB overexpression in metabolically engineered E. coli.     

The metabolic acclimation of Arabidopsis thaliana to arsenate is sensitized by the loss of mitochondrial LIPOAMIDE DEHYDROGENASE2, a key enzyme in oxidative metabolism

Mitochondrial lipoamide dehydrogenase is essential for the activity of four mitochondrial enzyme complexes central to oxidative metabolism. The reduction in protein amount and enzyme activity caused by disruption of mitochondrial LIPOAMIDE DEHYDROGENASE2 enhanced the arsenic sensitivity of Arabidopsis thaliana. Both arsenate and arsenite inhibited root elongation, decreased seedling size and increased anthocyanin production more profoundly in knockout mutants than in wild‐type seedlings. Arsenate also stimulated lateral root formation in the mutants. The activity of lipoamide dehydrogenase in isolated mitochondria was sensitive to arsenite, but not arsenate, indicating that arsenite could be the mediator of the observed phenotypes. Steady‐state metabolite abundances were only mildly affected by mutation of mitochondrial LIPOAMIDE DEHYDROGENASE2. In contrast, arsenate induced the remodelling of metabolite pools associated with oxidative metabolism in wild‐type seedlings, an effect that was enhanced in the mutant, especially around the enzyme complexes containing mitochondrial lipoamide dehydrogenase. These results indicate that mitochondrial lipoamide dehydrogenase is an important protein for determining the sensitivity of oxidative metabolism to arsenate in Arabidopsis.     

Glyoxylate metabolism and fatty acid oxidation in mango fruit during development and ripening

Throughout the development (maturation) of mango fruit the contents of citric and glyoxylic acids increased steadily. As the fruit matured the levels of isocitrate lyase, malate lyase and alanine: glyoxylate aminotransferase increased and reached maximum values prior to the time of harvesting. At and after harvest the levels of malate lyase and alanine : glyoxylate aminotransferase began to decrease but that of isocitrate lyase remained high until after the harvest when it decreased. The level of glyoxylate reductase was highest in the early developmental stage but declined as the fruit matured and ripened. As the fruit ripened, after harvest, the amounts of citric and glyoxylic acids decreased concomitant with a considerable increase in the levels of isocitrate dehydrogenase, malic dehydrogenase, malic enzyme and glyoxylate dehydrogenase.Fatty acid oxidizing capacity of mitochondria isolated from immature (developing) and postclimacteric fruit pulps was much less than that observed with mitochondria from preclimacteric and climacteric fruit. Glyoxylate stimulated the oxidation of caprylic, lauric, myristic and palmitic acids and inhibited the activity of isocitrate dehydrogenase in vitro.     

A Photorepressible Isozyme o Malic Enzyme in Euglena gracilis Strain Z*†

SYNOPSIS. Isozymes of malic enzyme in Euglena gracilis strain Z were analyzed by starch-gel electrophoresis. Wild-type and heat-bleached strains were cultured in the light and the dark in the presence of various carbon sources. An isozyme detectable in heterotrophic cultures was repressed by photosynthesis. A model is proposed to explain photorepression of this isozyme.     

Malic enzyme 1 genotype is associated with backfat thickness and meat quality traits in pigs

Malic enzyme 1 (ME1) is a part of the tricarboxylate shuttle that provides NADPH and acetyl-CoA required in fatty acid biosynthesis. The pig ME1 locus maps on the proximal end of chromosome 1, where a quantitative trait loci (QTL) affecting fat deposition has been previously described. We amplified fragments of 1457 and 1459 bp that corresponded to the complete coding region and the 3'-untranslated region (UTR), respectively, of the pig ME1 gene. The sequences of these two fragments in pigs from three breeds (Landrace, Large White and Piétrain) contained five single nucleotide polymorphisms (SNP) in the 3'-UTR: C1706T, G1762T, A1807C, C1857A and T1880A. Three haplotypes were found in two generations of a selected Landrace population: H1 (C1706 G1762 A1807 C1857 A1880), H2 (C1706 G1762 A1807 C1857 T1880) and H3 (T1706 T1762 C1807 A1857 T1880). Using Bayesian association analyses, significant associations (highest posterior density at 95%) between ME1 genotype and backfat (BF) thickness at 171 days and muscular pH were found in a Landrace population.     

Hymenolepis diminuta: Activity of anti-oxidant enzymes in different parts of rat gastrointestinal tract

The aim of this study was to assess the intensity of oxidative stress by measuring levels of lipid peroxidation products in the duodenum, jejunum and colon of rats infected with Hymenolepis diminuta and evaluate the effectiveness of protection against oxidative stress by measuring the glutathione levels and activity of anti-oxidant enzymes: superoxide dismutase, catalase, glutathione reductase and glutathione peroxidase.In exposed rats we observed a significant increase of lipid peroxidation products in the duodenum and jejunum. A significant decrease in superoxide dismutase activity in all the examined parts of the digestive tract was observed. Additionally, rats from 16 to 40 days post H. diminuta infection (dpi) had a decreased catalase activity in the colon, while at 60 dpi it increased. The glutathione peroxidase activity increased significantly in the colon at 60 dpi. The increase in glutathione reductase activity was observed in the colon in rats 60 dpi. There was a lack of changes in the levels of glutathione in the duodenum and a significant increase in its concentration in the jejunum and colon from 40 to 60 dpi and from 16 to 40 dpi, respectively. In this study we observed altered activity of anti-oxidant enzymes and glutathione level in experimental hymenolepidosis, as a consequence of oxidative stress. It may indicate a decrease in the efficiency of intestinal protection against oxidative stress induced by the presence of the parasite. The imbalance between oxidant and anti-oxidant processes may play a major role in pathology associated with hymenolepidosis.     

Genetic variation,inheritance, and quaternary structure of malic enzyme in brook trout (Salvelinus fontinalis)

Electrophoretic variation is described for malic enzyme (ME) for the first time in brook trout (Salvelinus fontinalis). Since the quaternary structure of ME was not clear from examination of banding patterns in brook trout alone, ME phenotypes in rainbow trout (Salmo gairdneri) × brook trout hybrids as well as in esocid species demonstrated that ME is tetrameric. A model of two duplicated loci is proposed to account for the observed variation. One locus (ME-2) is fixed and one locus (ME-1) is variable with three electrophoretically distinct alleles; the protein products of ME-1 are reduced in activity relative to the protein products of ME-2. Joint segregation was examined between ME-1 and ten other biochemical loci in brook trout, and between ME-1, ME-2, and nine other biochemical loci in a splake—lake trout (Salvelinus namaycush) × brook trout hybrid—backcross. All pairwise examinations showed random assortment except ME-2 with an isocitrate dehydrogenase locus (IDH-3), which showed complete linkage in the splake backcross. This may be due to a chromosomal aberration.Authorized for publication as Paper No. 5599 in the Journal Series of The Pennsylvania Agricultural Experiment Station, University Park, Pennsylvania, in cooperation with the Benner Spring Fish Research Station, The Pennsylvania Fish Commission, Bellefonte, Pennsylvania. M.S. was supported by an NSF Graduate Fellowship.     

Cloning and sequence analysis of the gene encoding Lactococcus lactis malolactic enzyme: Relationships with malic enzymes

Abstract Malolactic enzyme is the key enzyme in the degradation of L-malic acid by lactic acid bacteria. Using degenerated primers designed from the first 20 N-terminal amino acid sequence of lactococcal malolactic enzyme, a 60-bp DNA fragment containing part of the mleS gene was amplified from Lactococcus lactis in a polymerase chain reaction. This specific probe was used to isolate two contiguous fragments covering the gene as a whole. The 1.9-kb region sequenced contains an open reading frame of 1623 bp, coding a putative protein of 540 amino acids. The deduced amino acid sequence reveals that lactococcal putative protein (Mlep) is highly homologous to the malic enzyme of other organisms. Expression of the mleS gene in Escherichia coli results in malolactic activity.     

Protein and enzyme release from human leukocytes: influence of phenothiazine derivatives.

We studied the influence of chlorpromazine on the release of enzymes (beta-glucuronidase, EC 3.2.1.31; lactate dehydrogenase, EC 1.1.1.27; pyruvate kinase, 2.7.1.40) and proteins using human granulocytes isolated and maintained at 37 degrees C. Chlorpromazine had a biphasic effect on enzyme release and the inhibition of the glycolytic pathway could be demonstrated only at high concentrations of chlorpromazine, after one hour's incubation. The NAD+/NADH ratio was significantly perturbed at all the concentrations. This effect is time dependent. The action of 4 other phenothiazine derivatives made it possible to establish a relationship between their physico-chemical properties and protein release. The results are compared with those from other studies using other biological materials.     

Anaerobic metabolism enzymes as markers of flooding stress in maize seeds

Maize (Zea mays L.) seeds differ in their relative tolerance to the anaerobic environment caused by flooding. Seed tolerance to flooding stress depends on cellular and metabolic processes since gross anatomical responses have not developed at the pre-emergence stage. The study reported here characterizes the activities of four anaerobic respiratory enzymes: pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH), lactate dehydrogenase (LDH), and malic enzyme (ME) in the flood-tolerant A632 and floodsusceptible Mo 17 inbred maize seeds during flooding at 10 and 25°C. Each inbred consisted of two seed lots possessing 95% and 75% germination levels. Flooding increased the activities of all four enzymes. However, no consistent correlation between anaerobic enzyme activity and flood tolerance was observed across genotype, seed quality and flooding temperature. The results indicate that it may not be feasible to use whole-seed anaerobic enzyme activities to predict maize seed performance under flooding stress. Contribution from the Soil Drainage Research Unit, USDA-ARS, Columbus, OH, in cooperation with the Ohio Agricultural Research and Development Center, The Ohio State University. OARDC Journal Article No. 66–86.     

Succinate dehydrogenase and fumarate reductase activity in Aspiculuris tetraptera and Ascaris suum and the effect of the anthelmintics cambendazole,thiabendazole, and levamisole

Comley John C. W. and Wright Spdenis J. 1981. Succinate dehydrogenase and fumarate reductase activity in Aspiculuris tetraptera and Ascaris suum and the effect of the anthelmintics cambendazole, thiabendazole, and levamisole. International Journal for Parasitology11: 79–84. Succinate dehydrogenase and fumarate reductase activities from a particulate fraction of A. tetraptera and a soluble extract of A. suum have been determined using spectrophotometric methods. Fumarate reductase activity in A. suum could only be detected anaerobically. Succinate dehydrogenase activity from A. suum was partially characterized and shown to exist in several multimolecular forms (isoenzymes). The in vitro effect of the anthelmintics cambendazole, thiabendazole and levamisole on succinate dehydrogenase and fumarate reductase activity from the above nematodes are described. Significant inhibition of fumarate reductase activity of both nematodes was only achieved using 5 mM levamisole and 1 mM thiabendazole. After in vivo anthelmintic treatment of A. tetraptera only thiabendazole significantly inhibited fumarate reductase. It is suggested that the succinate dehydro-ogenase-fumarate reductase complex in these nematodes is unlikely to be the primary site chemotherapeutic attack for any of the anthelmintics tested.     

Variations de la malate déshydrogénase dans quatre espèces de Jaera albifrons: Etude génétique et variation géographique

Malate dehydrogenase has been detected in four species of the super-species Jaera albifrons. Two polymorphic enzymatic systems occur showing a one banded pattern for homozygotes and a three banded pattern for heterozygotes. Two independant autosomal loci control the variation as is shown by intra- and interspecific crosses. In European populations of the three species studied, MDH-1 is polymorphic and MDH-2 is monomorphic. In the American species, J. posthirsuta, the locus MDH-2 is polymorphic and MDH-1 is monomorphic.     

Electrophoretic variation at flight-related enzyme loci and its possible association with flight capacity inEpiphyas postvittana

Variations at three flight-related enzyme loci, -glycerophosphate dehydrogenase (-Gpdh), glucose-6-phosphate dehydrogenase (G6pd), and phosphoglucomutase (Pgm), ofEpiphyas postvittana (Walker) moths were investigated using starch gel electrophoresis. Among the three enzyme loci, -Gpdh andG6pd were found to be monomorphic, butPgm was polymorphic, with a total of seven different genotypes and five alleles identified in this study. Comparisons of allozyme variability at thePgm locus showed significant differentiation among five natural populations sampled from geographically distinct localities in New Zealand and Australia and between laboratory populations differentiated by artificial selection on flight capacity. ThePgm polymorphism was shown to be associated with the variation of flight capacity, but the role of the enzyme locus in the evolution of flight behavior is to be demonstrated in this species.This work was supported by the research scholarship of the University of New England.     

Comparison of glycolytic and associated enzyme activities in the claw and tail muscles of the lobster with those of the mantle of Mytilus edulis

In the mussel Mytilus edulis, the activities of phosphoenolpyruvate car?ykinase (PEP-CK) and of malate dehydrogenase (MDH) are greater than those of pyruvate kinase (PK) and lactate dehydrogenase (LDH). The activities of PEP-CK are very low in the lobster (H. vulgaris.) and the ratio of MDH/LDH activities are 0·041 and 1·83 in the tail and the claw muscles respectively. Intracellular L-lactate and L-alanine concentrations suggest a different carbohydrate utilization in the tail and the claw muscle of the lobster. Consistent with this finding is the fact that L-lactate concentration is higher in the tail muscle than in the claw muscle; the opposite is true for L-alanine concentrations.