• Volume 5, Issue 1

      March 1983,   pages  1-105

    • Non-identity of reaction centres for pyrophosphatase and toxic actions of cardiotoxin II: The status of cardiotoxin II as a metalloprotein

      K E Achyuthan L K Ramachandran

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      Cardiotoxin II of the Indian cobra(Naja naja) contains approximately four Mg2+ per mol. Complete demetallation of the toxin is achieved by three cycles of treatment with ethylenediamine tetraacetate and gel filtration. Reconstitution of toxin by treatment of the apo-protein with Mg2+ restores metal content and inorganic pyrophosphatase activity only to the extent of two atoms/mol and 65%, respectively. Use of Mg (II)-EDTA in the reconstitution experiment yields restoration of half the original enzyme activity. Mg2+ is required for the inorganic pyrophosphatase action of the toxin. A definitive statement on the non-essentiality of Mg2+ for the lethal toxicity of the toxin is not possible at present, although experimental observations indicate that demetallated toxin is as toxic as the native toxin. Based on this and the differing sensitivities of the enzyme and toxic activities of the toxin to heat, it is suggested that the reaction centres in the toxin for the two activities are different and that the pyrophosphatase activity is not causally connected with the lethal toxicity of the toxin

    • Naphthalene oxygenase fromCorynebacterium renale: Characterisation and mechanism of oxygenation

      Paluri S Rao Meera Srinivasan

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      The formation ofcis-l,2,-dihydroxy-l,2,-dihydronaphthalene from naphthalene by naphthalene oxygenase, purified fromCorynebacterium renale ATCC 15075, was demonstrated to involve oxidation of a mol NADH and consumption of one mol oxygen. The enzyme contains one g-atom Fe2+ and one FAD. Catalase inhibited product formation and H2O2 could substitute for NADH in the reaction. Superoxide dismutase inhibited enzyme activity when either NADH or H2O2 was present; the generation of superoxide anion on addition of NADH to the enzyme, in the absence of naphthalene, was detected by the nitro blue tetrazolium reduction method. Hydroxyl radical scavengers, ethanol, mannitol and sodium benzoate, inhibited product formation when either NADH or H2O2 was present. Electron spin resonance studies, under aerobic conditions, indicated that iron of the enzyme underwent valence changes during the course of the reaction

    • Enzyme inhibitors from plants. Isolation and characterization of a protease inhibitor from arrow root (Maranta arundinaceae) tuber

      N Mallikarjuna Rao H Nayana Rao T N Pattabiraman

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      A protease inhibitor from arrow root (Maranta arundinaceae) tuber has been isolated in a homogeneous form. The inhibitor has a Mr of 11,000-12,000; it inhibited bovine trypsin, bovine enterokinase, bovine α-chymotrypsin and the proteolytic activity of human and bovine pancreatic preparations. The inhibitor is resistant to pepsin, and elastase. It could withstand heat treatment at 100°C for 60 min and exposure to a wide range of pH (1.0–12.5) for 72 h at 4°C without loss of activity. Arginyl groups are essential for the action of the inhibitor. Preincubation of the inhibitor at pH 3.7 with trypsin or chymotrypsin caused nearly a two-fold increase in inhibitor potency

    • Studies on triacylglycerol ester hydrolase from bat adipose tissue

      Subhash S Patil Chanda K Bhandari Vijay A Sawant

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      Triacylglycerol ester hydrolase was isolated from bat adipose tissue and characterized. The partially purified enzyme had pH optimum of 8.6 and a Km value of 0.6 mM. The enzyme was denaturated upon freezing and thawing, which was prevented by 25% glycerol. The enzyme was activated by EDTA and NaCl, while it was inhibited by serum and bovine serum albumin. Heparin, sodium fluoride and diisopropyl fluorophosphate had no effect on triacylglycerol ester hydrolase activity. It hydrolyzed triglycerides partially. Triacylglycerol ester hydrolase lost its activity during delipidation but it was reactivated by endogenous lipids and phospholipids, viz. phosphatidyl ethanolamine, phosphatidyl choline and sphingomyelin. The enzyme shows kinetic properties altogether different from lipoprotein lipase and hormone sensitive lipase

    • Dipicolinic acid as a secondary metabolite inPenicillium citreoviride

      G P Kalle P S Khandekar

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      Synthesis of dipicolinic acid inPenicillium citreoviride showed typical kinetics of a secondary metabolite. Its synthesis resumed during idiophase and continued through stationary phase of growth. Total duration of synthesis was 100 h at the end of which its synthesis was arrested. Production of dipicolinic acid by the cells was subject to catabolite repression by glucose and was not subject to end product inhibition by exogenously added dipicolinic acid. Unlike the bacteria, dipicolinic acid synthesis in this mold was highly sensitive to inhibition by calcium ions in the growth medium. Calcium promoted sporulation but dipicolinic acid was not found to be present in detectable amounts in mold spores. Addition of dipicolinic acid and Ca2+ completely inhibited itsde novo synthesis, an effect not observed when calcium was replaced by Mg2+ When the mold was grown in the presence of calcium alone, its inhibitory effects onde novo synthesis of dipicolinic acid were expressed only after some of this metabolite was first synthesised by the producer cells suggesting that the active feedback inhibitor is probably a Ca: dipicolinic acid complex. It is suggested that over-production of this metabolite is very important to the mold in increasing its survival potential in nature by retrieving the essential minerals from the environment through ligand: metal complex at a time when cells are in the process of dying, so that a proper mineral balance is maintained within the cells

    • A new bioluminescent fungal system

      S C Sabharwal S P Kathuria M M Dhingra

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      A new bioluminescent fungal system from a wood sample with a characteristic emission around 518 ±1 nm is described. This study indicates that water is not only important for emission but has a function in the kinetics of the reaction

    • Phytochrome regulation of nitrate reductase in wheat

      O Ramaswamy I M Saxena Sipra-Guha Mukherjee Sudhir K Sopory

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      In excised wheat leaves, the activity of nitrate reductase was enhanced by a brief pulse of red light and this increase was reversed by far-red light irradiation. Even under continuous far-red light, nitrate reductase activity increased by 258% after 18 h. When leaves were kept in distilled water during exposure to red light and then transferred to potassium nitrate, there was no difference in endogenous nitrate concentration. The nitrate reductase activity was the same whether leaves were floated in potassium nitrate or in distilled water during irradiation. Partial to complete inhibition of enzyme activity was observed when leaves were incubated in actinomycin-D and cycloheximide respectively, following 4 h of red light irradiation.In vitro irradiation of extract had no significant effect on nitrate reductase activity

    • Correlation between inhibition of photosynthesis and growth ofChlorella treated with methyl parathion

      G Saroja Salil Bose

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      When methyl parathion (O,O-dimethyl O-p-nitrophenyl phosphorothioate), an organophosphorous insecticide, was added to an exponentially growing culture ofChlorella protothecoides and the effects were followed for 12 days, the following observations were made: a) In autotrophic culture the cell number and the chlorophyll content decreased as compared to the control. These changes paralleled the inhibition of the rate of net photosynthesis, suggesting that the photosynthetic apparatus was the primary target of the insecticide action. b) The inhibition of cell growth (on cell number basis) also occurred in the case of heterotrophic culture at 100μM insecticide concentration but the inhibition was less as compared to that of an autotrophic culture. c) The cell diameter in treated culture increased by 10–20% in both autotrophic and heterotrophic cultures. The observations, (b) and (c) suggest that apart from the photosynthetic apparatus, the insecticide has other sites of action, but the sensitivity of these sites to the insecticide is less than that of the photosynthetic apparatus

    • Increase in membrane permeability of electrolytes and betacyanin in beet root disc by fenitrothion

      Karunyal Jesudian Salil Bose

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      Effect of fenitrothion (phosphorothioic acid, 0,0-dimethyl 0-4-nitro-m-tolyl ester), an organophosphorous insecticide, on membrane permeability employing the leakage of betacyanin and electrolytes as the criteria were studied in beet root(Beta vulgaris) discs. The leakage of both betacyanin and electrolytes increased with increasing concentrations (10–150 ppm) of fenitrothion in the incubation medium. At 0.33 mM the increase in electrolyte leakage was approximately linear for the first 6h, while the increase in betacyanin leakage started with a lag of about 2 h. Long term incubation (24 h) showed a biphasic nature (in the semilog plot) for the increase in betacyanin leakage, while the increase in electrolyte leakage appeared more complex. In the control sample, the Arrhenius plots (25–50°C) of leakage showed a break at 40°C. In treated samples no break was observed, but the slope decreased (for both electrolyte and betacyanin leakage) as compared to the respective slopes in the control in the temperature region greater than 40°C. The results are discussed in terms of the possible effect of the insecticide on the active transport in plant membranes

    • Suppression of auxin stimulated growth of barley coleoptile sections by endosulfan

      S Agarwal M U Beg C R Krishna Murti

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      Endosulfan, a cyclic sulphurous acid ester commonly used as a broad spectrum insecticide, suppressed the elongation of barley coleoptiles. Indoleacetic acid at optimum concentration overcame the inhibition of growth of coleoptiles treated with 10 ppm endosulfan. However, perfusion of the coleoptile sections with endosulfan and subsequent treatment with indoleacetic acid could not stimulate cell elongation to the extent observed in the control

    • Effect of malathion and acetylcholine on the developing larvae ofPhilosamia ricini (Lepidoptera: Saturniidae)

      Radha Pant S K Katiyar

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      Feeding of malathion induces accumulation of acetylcholine inPhilosamia ricini developing larvaevia inhibition of acetyl cholinesterase activity. The insecticide also causes depletion of all nutrients, loss in weight, under-development of silk glands resulting in reduced silk production, lack of oviposition and high mortality among the insects. Acetylcholine however, while fed during the same period of development, tones up their nutritional status, induces better growth, weight gain, improved silk production and oviposition and significantly lower mortality than in the control group of insects maintained on castor leaves. This improved status of insects has been attributed to choline, the insect vitamin released from acetylcholine. Acetylcholine has also been noted to protect the insects to some extent from the poisonous effect of malathion on exposure to it after a dose of acetylcholine during the preceding instar stadium

    • Survival of orally administered isolated intestinalLactobacillus acidophilus in different parts of gastrointestinal tract of mice

      Pramatha R Bhattacharya M K Majumdar

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      A strain ofLactobacillus acidophilus (Strain HF) was isolated from human faeces. A chloramphenicol resistant strain (HFCm) and a strain (HFCmSm) restant to both chloramphenicol and streptomycin were developed from the isolated strain (HF). All the three strains showed similarin vitro susceptibility against host defence factors like gastric acid, bile salts and volatile as well as non-volatile fatty acids.In vivo tests were done by feeding these strains to mice. When the resistant strains were orally administered along with the antibiotic(s) they were stable up to 72 h

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