Descripción: Fil:Torres, H.N. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: Fil:del C. Batlle, A.M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: Fil:Chelala, C.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: Fil:Tigier, H.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: An enzyme, aminolaevulinate dehydratase (5-aminolaevulinate hydro-lyase (adding 5-aminolaevulinate and cyclizing), EC 4.2.1.24), which catalyzes the following reaction: {A figure is presented} has been isolated from yeast. Its purification and some of its properties have been studied. 5-Aminolaevulinate synthetase, another enzyme involved in porphyrin biosynthesis, has been detected in the mitochondrial particles. © 1967.

Descripción: Cysteine proteinase isoforms, immunologically cross-reactive with cruzipain and with a similar apparent molecular mass, have been identified in epimastigotes of Trypanosoma cruzi by extraction and phase partition using the detergent Triton X-114. These isoforms are concentrated in the microsomal fraction obtained after differential centrifugation, which is known to consist essentially of plasma membrane, can be labelled by incubation of live parasites with sulfo-NHS-biotin, and bind to cystatin-sepharose affinity columns. They are present, albeit with a different electrophoretic pattern, in the epimastigote, amastigote and trypomastigote stages of the parasite.

Descripción: 1. 1. By chromatography through Sephadex G-200 of increasing amounts of partially purified pig liver ALA-D, different profiles were obtained, showing that species of molecular weights ranging from 140,000 to 560,000 might exist in equilibrium, but their relative ratio was dependent on the total amount of protein sampled. In all cases, however, the main peak (60-70%) corresponded to the 280,000 MW oligomer, that is the octamer. 2. 2. It was found that elution profiles were also dependent on column dimensions and on the purity of the enzyme preparation. 3. 3. K+ ions affected both catalytic activity and aggregation of the enzyme. 4. Results here reported add further support to the proposal of the existence of a minimal functional dimer. © 1980.

Descripción: 1. 1. The inactivation of phosphorylase a phosphatase decreased the maximum velocity of the phosphorylase a to phosphorylase b conversion reaction when it was assayed at different phosphorylase a concectrations. 2. 2. Maximal phosphorylase a phosphatase activities were found between pH 8 and 8.3. Inactivation of the phosphorylase a phosphatase led to a decrease in the activity in all the pH ranges tested. 3. 3. Theophylline and caffeine stimulated the phosphorylase a phosphatase. The effect of these substances was exerted in the reaction assay of the enzyme. 4. 4. ATP, ADP, AMP, GTP, UTP, CTP and pyrophosphate were found to decrease the rate of the reaction catalyzed by phosphorylase a phosphatase. This effect showed a striking parallelism with the capacity of these compounds to stimulate the phosphatase inactivation. © 1970.

Descripción: 1. 1. The incubation of the pegion breast muscle homogenate at 37° resulted in a time-dependent decrease in phosphatase activity. This effect was stimulated by ATP, ADP, AMP, GTP, UTP, CTP or pyrophosphate. 2. 2. Reactivation of an inactive phosphorylase a phosphatase preparation was obtained by incubation with ATP-Mg2+. Phosphocreatine-Mg2+ or Mg2+ were also found to be effective in bringing about the reactivation of the enzyme. 3. 3. 3′,5′-Cyclic AMP decreased the yield of the active enzyme when it was added either at the beginning or during the activation reaction. © 1970.

Descripción: 1. 1. Gel filtration on Sephadex G-100 and Sepharose 4B were used to redetermine the molecular weight (MW) of porphobilinogenase, deaminase and isomerase purified from different sources, and determine the MW of these enzymes purified from Eugtena gracilis. 2. 2. Results reported here, indicate that porphobilinogenase can be found, into three different molecular forms, tetramers, dimers and monomers according to the source organism. 3. 3. It is proposed that minimal functional structure of PBGase is a hybrid protomer of MW 25,000, composed by two different domains, in a ratio of 1 mol of deaminase, MW 20,000 to 1 mol of isomerase. MW 5000. 4. 4. A model explaining the occurrence of different MW species of PBGase in nature and the possible interconversion among the various forms is postulated. © 1980.

Descripción: The high levels of δ-aminolevulinate synthetase (ALA-S) in Rhodopseudomonas palustris cells grown anaerobically in the light (Ph) decrease to those found in cells grown aerobically in the dark (A), when the former cultures were vigorously oxygenated; simultaneously bacteriochlorophyll (Bchl) synthesis abruptly halted leading to diminished steady-state specific Bchl content. When flushing oxygen was interrupted, enzymic activity increased, whether chloramphenicol was present or not in the medium; if the protein synthesis inhibitor was added when oxygenation started, ALA-S declined in the same fashion as in its absence, but thereafter reactivation of the enzyme was lower than before. Succinyl-CoA-synthetase and ALA-dehydratase activities were also measured under the conditions described, and no changes at all have been observed. The existence of different forms of ALA-S in R. palustris depending on growth conditions is postulated along with the formation of low molecular weight factors which can modulate ALA-S activity by binding to the enzyme; a widespread mechanism in the adaptation of micro-organisms to changes in environment. It is also proposed that this particular regulatory phenomenon, could be referred to as a switch off/on mechanism controlling ALA-S activity in R. palustris. © 1987.

Descripción: In flowering plants, the process of pollen germination and tube growth is required for successful fertilization. A pollen receptor kinase from tomato (Solanum lycopersicum), LePRK2, has been implicated in signaling during pollen germination and tube growth as well as in mediating pollen (tube)-pistil communication. Here we show that reduced expression of LePRK2 affects four aspects of pollen germination and tube growth. First, the percentage of pollen that germinates is reduced, and the time window for competence to germinate is also shorter. Second, the pollen tube growth rate is reduced both in vitro and in the pistil. Third, tip-localized superoxide production by pollen tubes cannot be increased by exogenous calcium ions. Fourth, pollen tubes have defects in responses to style extract component (STIL), an extracellular growth-promoting signal from the pistil. Pollen tubes transiently overexpressing LePRK2-fluorescent protein fusions had slightly wider tips, whereas pollen tubes coexpressing LePRK2 and its cytoplasmic partner protein KPP (a Rop-GEF) had much wider tips. Together these results show that LePRK2 positively regulates pollen germination and tube growth and is involved in transducing responses to extracellular growth-promoting signals. © 2008 American Society of Plant Biologists.

Descripción: Ethylene inhibits the establishment of symbiosis between rhizobia and legumes. Several rhizobia species express the enzyme ACC deaminase, which degrades the ethylene precursor 1-cyclopropane-1-carboxilate (ACC), leading to reductions in the amount of ethylene evolved by the plant. M. loti has a gene encoding ACC deaminase, but this gene is under the activity of the NifA-RpoN- dependent promoter; thus, it is only expressed inside the nodule. The M. loti structural gene ACC deaminase (acdS) was integrated into the M. loti chromosome under a constitutive promoter activity. The resulting strain induced the formation of a higher number of nodules and was more competitive than the wild-type strain on Lotus japonicus and L. tenuis. These results suggest that the introduction of the ACC deaminase activity within M. loti in a constitutive way could be a novel strategy to increase nodulation competitiveness of the bacteria, which could be useful for the forage inoculants industry.

Descripción: The possible involvement of apoplastic reactive oxygen species produced by the oxidation of free polyamines in the leaf growth of salinized maize has been studied here. Salt treatment increased the apoplastic spermine and spermidine levels, mainly in the leaf blade elongation zone. The total activity of polyamine oxidase was up to 20-fold higher than that of the copper-containing amine oxidase. Measurements of H2O2, ·O2-, and HO· production in the presence or absence of the polyamine oxidase inhibitors 1,19-bis- (ethylamine)-5,10,15 triazanonadecane and 1,8-diamino-octane suggest that, in salinized plants, the oxidation of free apoplastic polyamines by polyamine oxidase by would be the main source of reactive oxygen species in the elongation zone of maize leaf blades. This effect is probably due to increased substrate availability. Incubation with 200 μM spermine doubled segment elongation, whereas the addition of 1,19-bis-(ethylamine)-5,10,15 triazanonadecane and 1,8-diamino-octane to 200 μM spermine attenuated and reversed the last effect, respectively. Similarly, the addition of MnCl2 (an ·O2- dismutating agent) or the HO· scavenger sodium benzoate along with spermine, annulled the elongating effect of the polyamine on the salinized segments. As a whole, the results obtained here demonstrated that, under salinity, polyamine oxidase activity provides a significant production of reactive oxygen species in the apoplast which contributes to 25-30% of the maize leaf blade elongation.

Descripción: 1. 1.|Porphobilinogenase has been isolated and purified from cow liver and its components, porphobilinogen deaminase and uroporphyrinogen isomerase, have been separated from each other and purified. 2. 2.|The effect of NH4+ was studied. The deaminase exhibited classical Michaelis-Menten kinetics in the absence or presence of NH4+, which at high concentrations behaved as a noncompetitive inhibitor of the deaminase. As expected from Hill plots, n = 1 both in the absence or presence of NH4+. Instead, when activity of porpho bilinogenase is plotted versus porphobilinogen concentration, sigmoid curves are obtained; but the presence of NH4+ at different concentrations altered the kinetic parameters of this enzymic system, again showing normal kinetics. In addition, n values were found to be 2 for porphobilinogen per porphobilinogenase molecule and 1 in the presence of NH4+ which behaves as a competitive inhibitor of the isomerase. Results are discussed in relation to the allosteric theories of monod et al.1,2 and liver porphobilinogenase is proposed to be an allosteric protein. 3. 3.|The presence of an ultrafiltrable factor which stimulates uroporphyrinogen formation from porphobilinogen has been revealed. © 1969.

Descripción: Removal of the poly(A) tail is the first step in the degradation of many eukaryotic mRNAs. In metazoans and yeast, the Ccr4/Caf1/Not complex has the predominant deadenylase activity, while the Pan2/Pan3 complex may trim poly(A) tails to the correct size, or initiate deadenylation. In trypanosomes, turnover of several constitutively-expressed or long-lived mRNAs is not affected by depletion of the 5'-3' exoribonuclease XRNA, but is almost completely inhibited by depletion of the deadenylase CAF1. In contrast, two highly unstable mRNAs, encoding EP procyclin and a phosphoglycerate kinase, PGKB, accumulate when XRNA levels are reduced. We here show that degradation of EP mRNA was partially inhibited after CAF1 depletion. RNAi-targeting trypanosome PAN2 had a mild effect on global deadenylation, and on degradation of a few mRNAs including EP. By amplifying and sequencing degradation intermediates, we demonstrated that a reduction in XRNA had no effect on degradation of a stable mRNA encoding a ribosomal protein, but caused accumulation of EP mRNA fragments that had lost substantial portions of the 5' and 3' ends. The results support a model in which trypanosome mRNAs can be degraded by at least two different, partially independent, cytoplasmic degradation pathways attacking both ends of the mRNA. © 2009 The Author(s).

Descripción: 1. 1. The activity of Succinyl CoA Synthetase (Suc CoA-S), Cysthationase, Rhodanese, Aminolevulinate Synthetase (ALA-S) and Aminolevulinate Dehydratase (ALA-D) was studied in old (405-407 subcultures) and young (34-36 subcultures) soybean callus clones as a function of the days of growing. 2. 2. Suc CoA-S, ALA-S and ALA-D activities were much lower in old than in young callus, while the activity of Cysthationase and Rhodanese was higher in old callus. 3. 3. ALA-S reached its maximum activity when Rhodanese and Cysthationase their minimum, on the 11th day of growth. It is suggested that the cellular content of a possible thio-compound which would regulate ALA-S activity, is controlled through its degradation by Rhodanese. © 1980.

Descripción: 1. 1. Uroporphyrinogen carboxy-lyase (EC 4.1.1.d), the enzyme catalysing the decaroxylation of uroporphyrinogen to coproporphyrinogen, has been isolated from normal chicken erythrocytes. The enzyme was purified 220-fold with a yield of 24% from haemolysate supernatant by DEAE-cellulose batch treatment, (NH4)2SO4 fractionation and chromatography on DEAE-cellulose. 2. 2. The purified material appears to be homogeneous in polyacrylamide gel disc electrophoresis. 3. 3. The enzyme was heat labile and inhibited by sodium salt; the activity was enhanced by EDTA, GSH and boiled rat-liver extract. 4. 4. The influence of these chemical and physical agents on the removal of the first and second carboxyl groups from uroporphyrinogen was compared; the second group was more susceptible to these agents. 5. 5. The possibility that one or several enzymes were involved in the stepwise decarboxylation of uroporphyrinogen is discussed. 6. 6. The general name of porphyrinogen carboxy-lyase for the enzyme system is proposed because of the different porphyrinogens it can decarboxylate. © 1970.

Descripción: The cyclic AMP (cAMP)-dependent protein kinase A (PKA) signaling pathway plays a role in regulating development, growth, and virulence in a number of fungi. To determine whether PKA plays a similar function in zygomycete fungi, a mutant of Mucor circinelloides was generated that lacks pkaR1, one of the regulatory subunits of PKA. The mutant showed a reduction in growth and alterations in germination rates, cell volume, germ tube length, and asexual sporulation. The lack of pkaR1 gene resulted in a highly decreased, but not null, cAMP binding activity and in a protein kinase activity that was still dependent on cAMP, although with a higher -/+ cAMP activity ratio, suggesting the existence of other cAMP binding activities. Consequently, three proteins analogous to pkaR1 were predicted from the recently sequenced genome of M. circinelloides and were named pkaR2, pkaR3, and pkaR4. Two of the proteins, pkaR2 and pkaR3, with cAMP binding activity were isolated from the wild-type strain and identified by mass spectrometry. The expression of all genes was detected at the mRNA level by semiquantitative reverse transcription-PCR, and they showed a differential expression at different developmental stages. This is the first time that a fungus is reported to have more than one gene encoding the regulatory subunit of PKA. © 2009, American Society for Microbiology.

Descripción: • Background and Aims: Trees with a partial leaf-shedding pattern and other morphological features a priori considered intermediate between those of the deciduous Nothofagus antarctica (G. Forster) Oersted and the evergreen N. dombeyi (Mirb.) Oersted (Nothofagaceae) were found in natural stands. The hybridization between a deciduous and an evergreen species of Nothofagus has not been reported so far in natural communities. • Methods: The putative hybrids and the two presumed parental species were compared using 14 enzyme systems as well as shoot, leaf and reproductive morphology. • Key Results: Six enzyme systems showed good resolution (MDH-B, IDH, SKDH, 6-PGDH, GOT and PGI) and in four of them (PGI, MDH-B, SKDH and 6-PGDH) the putative hybrids showed intermediate zymogram patterns between N. antarctica and N. dombeyi. Both principal coordinates analysis on isozyme data and principal components analysis (PCA) on quantitative morphological traits of shoots and leaves separated both parental species and located the putative hybrids closer to N. antarctica than to N. dombeyi. In the PCA, the number of basal cataphylls and the length:width ratio of leaves were the variables most discriminating among shoots of the three entities. The putative hybrids were intermediate between both species regarding leaf vernation, outline and venation, variation in leaf shape (length/width) with position on the parent shoot and in staminate inflorescence and cupule morphology. For other morphological traits, the putative hybrids resembled one of the parental species or differed from both species (e.g. valve morphology). • Conclusions: Isoenzymatic and morphological data sets support the idea of the hybrid nature (probably F 1 generation) of the semi-deciduous trees found. Nothofagus antarctica and N. dombeyi are probably more closely related than previously assumed. The relevance of pollen type in revealing evolutionary relationships between Nothofagus species is supported, and that of leaf-shedding pattern is rejected. © 2004 Annals of Botany Company.