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J J Cazzulo

Publications and source records attributed to J J Cazzulo.

At least 109 records · Page 6Linked to original sources
PubMed1980

Intracellular distribution of carbon dioxide-fixing enzymes in Trypanosoma cruzi and Crithidia fasciculata.

The intracellular distribution of phosphoenopyruvate carboxykinase (EC 4.1.1.49) and NADP-linked malic enzyme (EC 1.1.1.40) activity in epimastigotes of Trypanosoma cruzi (Tulahuén strain) and in Crithidia fasciculata has been studied by two procedures: (i) subcellular fractionation by differential centrifugation of homogenates obtained by breaking the cells in a mortar; (ii) selective disruption of cellular membranes by digitonin treatment. Phosphoenolpyruvate carboxykinase is particulate in both organisms, as is one of the two forms of malic enzyme present in T. cruzi (malic enzyme I), whereas the other malic enzyme of T. cruzi (malic enzyme II) and the single malic enzyme of C. fasciculata are in the cytosol.

Citrate (si)-Synthase↗
PubMed1980

Some properties of the NADP-specific malic enzyme from the moderate halophile Vibrio costicola.

NADP-specific malic enzyme (EC 1.1.1.40) has been purified about 160-fold from the moderate halophile Vibrio costicola. The enzyme has a molecular weight of about 120,000. The purified enzyme was unstable in dilute solutions but could be stabilised by NaCl or glycerol. NH4Cl or KCI caused maximal activation at 0.1M, but higher concentrations were inhibitory. NaCl did not activate and was instead a mixed-type inhibitor towards NH4Cl or KCI. The salt concentration affected the kinetic parameters of the reaction. The apparent Km for L-malate reached a minimal value at about 0.1 M salt; the value for NADP, on the other hand, increased continuosly with the Co2+ or Mg2+. NADH was a mixed-type inhibitor towards both substrates, whereas oxaloacetate was strictly competitive towards L-malate and non-competitive towards NADP. The inhibition kinetics were sigmoidal for NADH and hyperbolic for oxaloacetate. The malic enzyme form V. costicola was similar to those of a marine Pseudomonas and Halobacterium cutirubrum in kinetic and regulatory properties but showed a response to salts intermediate between those of the latter enzymes.

Ammonium Chloride↗
PubMed1979

Two forms of 'malic' enzyme with different regulatory properties in Trypanosoma cruzi.

1. Cell-free extracts from culture epimastigotes of Trypanosoma cruzi contained two forms of NADP+-linked 'malic' enzyme (EC 1.1.1.40), I and II, with the same molecular weight but different electrophoretic mobilities and kinetic and regulatory properties. 2. The apparent Km for L-malate was lower for 'malic' enzyme I, with hyperbolic kinetics, whereas the kinetic pattern for 'malic' enzyme II was slightly sigmoidal (h 1.4). The kinetics for NADPH were hyperbolic for 'malic' enzyme I, and very complex for 'malic' enzyme II, suggesting both positive and negative co-operativity. 3. 'Malic' enzyme II was markedly inhibited by adenine nucleotides; AMP was the the most effective, at least in the presence of an excess of MnCl2. 'Malic' enzyme I was much less affected by the nucleotides. Both enzyme forms were inhibited by oxaloacetate, competitively towards L-malate, but the apparent Ki for 'malic' enzyme I (9 microM) was 10-fold lower than the value for 'malic' enzyme II. 'Malic' enzyme II, but not 'malic' enzyme I, was activated by L-aspartate and succinate (apparent Ka of 0.12 and 0.5 mM respectively); the activators caused a decrease in the apparent Km for L-malate and, to a lesser extent, in the apparent Km for NADP+. L-Aspartate, but not succinate, increased the apparent Vmax. 4. The inhibition by AMP suggests regulation by energy charge, with the L-malate-decarboxylation reaction catalysed by 'malic' enzyme II fulfilling a biosynthetic role. The inhibition by oxaloacetate and the activation by succinate are probably involved in the regulation of the 'partial aerobic fermentation' of glucose which yields succinate as final product. The activation by L-aspartate would facilitate the catabolism of this amino acid, when present in excess in the growth medium.

Adenine Nucleotides↗
PubMed1979

Inhibition of the NADP-linked glutamate dehydrogenase from Trypanosoma cruzi by sulfhydryl reagents.

1. The NADP-linked glutamate dehydrogenase purified from epimastigotes of Trypanosoma cruzi was strongly, but not completely, inhibited by sulfhydryl reagents, in the presence of Tris-HCl or phosphate buffers. 2. The enzyme modified by preincubation with o-iodosobenzoate had a kinetic behaviour different from that shown by the enzyme modified with other inhibitors, such as N-ethylmaleimide or p-chloromercuribenzoate. 3. The inhibition by o-iodosobenzoate was additive with the inhibition by the other reagents tested. 4. It is suggested that two or more different sulfhydryl groups, placed probably near the active site, are involved in these effects.

Animals↗
PubMed1979

NAD-linked glutamate dehydrogenase in Trypanosoma cruzi.

1. Epimastigotes of Trypanosoma cruzi, Tulahuén strain, contained a NAD-linked glutamate dehydrogenase (EC 1.4.1.3), in addition to the already known NADP-linked enzyme enzyme (EC 1.4.1.4). 2. The partially purified NAD-linked enzyme had a higher molecular weight and was much more labile than the NADP-linked enzyme, and was inhibited by purine nucleotides. 3. These results further emphasize the difference in glutamate metabolism between the parasite and its mammalian host.

Animals↗
PubMed1978

Adenosine triphosphatase activities in Trypanosoma cruzi.

1. Subcellular fractions obtained from epimastigotes of Trypanosoma cruzi, disrupted by three different procedures, contained in addition to the already known Mg2+-activated adenosine triphosphatase (ATPase; E.C.3.6.1.4), a Ca2+-ATPase activity. 2. The Ca2+-ATPase (a) was activated by low concentrations of CaCl2 (apparent Ka, 80 microM); (b) had a Km for ATP of 0.6 mM (at 1 mM CaCl2, pH 8.0); (c) presented a broad pH curve (optimum 7.1-8.6); and (d) was insensitive to oligomycin concentrations which inhibited the Mg2+-ATPase present in the same preparations. 3. All attempts to find a (Na+-K+)-activated, ouabain-inhibited, ATPase have been unsuccessful, in spite of the fact that living epimastigoes of T. cruzi are able to concentrate K+ and exclude Na+ from the medium.

Adenosine Triphosphatases↗
PubMed1978

Solubilization and some properties of the Mg2+-activated adenosine triphosphatase from Trypanosoma cruzi.

1. Grinding of epimastigotes of Trypanosoma cruzi with glass powder in a mortar yielded a Mg2+-activated adenosine triphosphatase (ATPase) preparation which was highly sensitive to oligomycin. 2. Chloroform treatment of the particles resulted in the solubilization of an ATPase which was (a) activated by MgCl2; (b) slightly inhibited by CaCl2; (c) activated by sulphite and bisulphite; (d) had an optimum pH of 7.6; and (e) had a Km for ATP of 2.1 mM (in the presence of 4 mM MgCl2). 3. The solubilized enzyme was insensitive to oligomycin and leucinostatin, which inhibited the membrane-bound ATPase, though inhibited by efrapeptin and quercetin. 4. The results indicate that the chloroform-extracted enzyme is a soluble F1-ATPase similar to those isolated from mammalian mitochondria.

Animals↗
PubMed1978

Purification and some properties of the citrate synthase from a marine Pseudomonas.

Citrate synthase (citrate-oxaloacetate lyase (CoA acetylating), EC 4.1.3.7) has been purified to electrophoretic homogeneity from a marine Pseudomonas. The enzyme was made up of identical subunits, with a molecular wieght of about 53 000, as determined by sodium dodecyl sulphate - polyacrylamide gel electrophoresis. The native enzyme (citrate synthase II, CS II) could be dissociated by dialysis against 20 mM phosphate (Pi), pH 7; the enzyme thus obtained (citrate synthase I, CS I) was still active, but presented different molecular weight and kinetic and regulatory properties. CS II was activated by adenosine monophosphate (AMP), Pi, and KCl, and inhibited by reduced nicotinamide adenine dinucleotide (NADH), being apparently insensitive to adenosine triphosphate (ATP) and adenosine diphosphate (ADP). The inhibition by NADH was completely counteracted by 0.1 mM AMP, but not by 50 mM Pi or 0.1 M KCl. The activation by KCl and Pi, or by KCl and AMP was nearly additive, whereas that by AMP and Pi was not. The activators acted essentially by increasing Vmax, although they also caused a decrease in the Km values. CS I was inhibited by ATP, ADP, AMP, and KCl, and was insensitive to NADH. CS I could be reassociated after elimination of Pi by dialysis, regaining the higher molecular weight and the activation by AMP characteristic of CS II.

Adenine Nucleotides↗
PubMed1977

Glutamate dehydrogenase and aspartate aminotransferase in Trypanosoma cruzi.

1. The cultured, epimastigote-form of Trypanosoma cruzi contains NADP-linked glutamate dehydrogenase (EC 1.4.1.4), with a molecular weight of about 280,000, similar to the enzyme from Plasmodium chabaudi and different from the enzymes from higher animal sources. 2. T. cruzi also contains aspartate aminotransferase (EC 2.6.1.1), with properties similar to those of the enzyme from mammals. 3. The concerted action of the transaminase and glutamate dehydrogenase might be responsible for the production of NH3 which characterizes the protein catabolism in T. cruzi.

Animals↗
PubMed1976

The citrate synthase from Bacillus Stearothermophilus.

Citrate synthase has been purified to apparent homogeneity from Bacillus stearothermophilus. Its kinetic and regulatory properties, and molecular weight, are similar to those of the enzymes from suitable mesophilic counterparts, but its thermal stability is considerably greater.

Citrate (si)-Synthase↗