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At least 37 records · Page 2Linked to original sources
PubMed1979

Nucleoside phosphotransferase from yellow lupin seedling cotyledons.

Nucleoside phosphotransferase (nucleotide:3'-deoxynucleoside 5'-phosphotransferase, EC 2.7.1.77) from yellow lupin seedling cotyledons was purified and the active enzyme consists of a single polypeptide chain, Mr = 72 000 +/- 3000. In transphosphorylation, purine and pyrimidine nucleosides are good phosphate acceptors and 5'-nucleotides are effective phosphate donors. Among 2'- and 3'-nucleotides, only 3'-AMP and 3'-psi MP acted as phosphate donors, and p-nitrophenylphosphate appeared less active in this regard. The purine and pyrimidine bases inhibit transphosphorylation. The Km values determined for the inosine:5'-AMP pair were 400 micrometers for both the compounds. The enzyme showed optimum activity at pH 8.0 in mM Tris-HCl buffer. Antisulfhydryl reagents and EDTA did not affect enzyme activity.

Chemical Phenomena↗
PubMed1979

Some properties of starch phosphorylase from cotyledons of germinating seeds of Voandzeia subterranea.

Two isoenzymes (Forms I and II) of starch phosphorylase (1,4-alpha-D-glucan: orthophosphate alpha-glucosyltransferase, EC 2.4.1.1) were found in cotyledons of germinating seeds of Voandzeia subterranea L. Thouars. Phosphorylase I, which was the major component, had a pH optimum of 5.5--5.6, whereas phosphorylase II had a pH optimum of 6.1--6.3. Phosphorylase I had a molecular weight of 204 000 +/- 4000 and a subunit molecular weight of about 95 000. Phosphorylase I was stimulated by Mg2+, Mn2+, AMP, cyclic AMP, pyruvate and EDTA, but inhibited by Fe2+, Cu2+, Zn2+ and ATP. Stimulation of phosphorulase I by AMP was accompanied by changes in the affinity of the enzyme for glucose-1-phosphate in the presence of increasing AMP concentrations, and of AMP in the presence of increasing glucose-1-phosphate concentrations. Double-reciprocal plots of initial velocity data were non-linear (convex up) at low glucose-1-phosphate concentrations but became linear in the presence of AMP or ATP. Double-reciprocal plots were linear at high glucose-1-phosphate concentrations in the absence or presence of modifiers.

Adenosine Monophosphate↗
PubMed1979

Purification to homogeneity and some properties of L-phenylalanine ammonia-lyase of irradiated mustard (Sinapis alba L.) cotyledons.

1. Lyase (L-Phenylalanine ammonia-lyase, EC 4.3.1.5) from far-red light-irradiated mustard cotyledons was purified to a single protein using ammonium sulphate fractionation, column chromatography on L-phenylalanyl-Sepharose 4B and on Sephadex G-200, isoelectric focusing and polyacryalmide gel electrophoresis. 2. The enzyme constituted 0.01% of total cellular protein, did not catalyse the deamination of L-tyrosine, had a pH optimum of pH 8.6 and an isoelectric point of pH 5.6. 3. The sedimentation coefficient was estimated as 11.3 S, the Stokes' radius 4.25 nm, and the molecular weight 240 000 +/- 9000 (S.E.). 4. Electrophoresis on denaturing polyacrylamide gels gave a single stained protein band corresponding to a subunit molecular weight of 55 000 indicating a tetrameric structure of equal (or near-equal) size subunits. 5. Maximum velocity (V) for the purified lyase at 25 degrees C was 3.83--4.10 nkat. 1(-1) enzyme and Km value 0.151--0.154 mM. Negative cooperativity (Hill coefficient, n = 1.08) was not detected over the substrate concentration range tested. 6. A putative non-diffusible inhibitor isolated from dark-grown gherkin hypocotyls inhibited the homogeneously purified mustard lyase.

Ammonia-Lyases↗
PubMed1978

Rapid temperature-induced changes in the fatty acid composition of certain lipids in developing linseed and soya-bean cotyledons.

A change in ambient temperature caused marked alterations, over a 24h period, in the proportions of the unsaturated C18 fatty acids in 3-sn-phosphatidylcholine and 1,2-diacyglycerols during the development of soya-bean and linseed cotyledons. The molar proportion of oleate increased when the temperature was increased whereas that of linoleate or linolenate, depending on the species, increased when the temperature was lowered. Concomitant changes in the composition of 3-sn-phosphatidylethanolamine and triacylglycerols were small.

Diglycerides↗
PubMed1979

Evidence for an oleoyl phosphatidylcholine desaturase in microsomal preparations from cotyledons of safflower (Carthamus tinctorius) seed.

1. [14C]Oleoyl-CoA was metabolized rapidly and essentially completely by microsomal preparations from developing safflower (Carthamus tinctorius) cotyledons, and most of the [14C]oleate was incorporated into 3-sn-phosphatidylcholine. 2. In aerobic reaction mixtures containing NADH2 the [14C]oleate in 3-sn-phosphatidylcholine was converted into [14C]linoleate without any change in the specific radioactivity of the lipid. Over a 60 min incubation period the extent of conversion of [14C]oleoyl phosphatidylcholine into [14C]linoleoyl phosphatidylcholine was generally greater than 60%. The rate of desaturation of endogenous [14C]oleoyl phosphatidylcholine labelled from [14C]oleoyl-CoA was much greater that of exogenous [14C]dioleoyl phosphatidylcholine the specific radioactivity of the oleoyl moiety of the lipid remained constant, indicating that labelled and unlabelled oleate were desaturated at the same rate. On this assumption an initial rate of desaturation of about 15 nmol of oleate desaturated/min per mumol of 3-sn-phosphatidylcholine was estimated. 4. [14C]Oleate esterified at positions 1 and 2 of both endogenous and exogenous 3-sn-phosphatidylcholine was desaturated. 5. Attempts to demonstrate the presence of an oleoyl-CoA desaturase in safflower microsomal fractions by the appearance of linoleoyl-CoA in reaction mixtures were inconclusive.

Acyl Coenzyme A↗
PubMed1978

Localization of vicilin peptidohydrolase in the cotyledons of mung bean seedlings by immunofluorescence microscopy.

Vicilin peptidohydrolase, the protease that hydrolyzes the reserve proteins in the cotyledons of mung bean (Vigna radiata) seedlings, has been localized intracellularly by immunofluorescence microscopy using monospecific antibodies against the enzyme and rhodamine-coupled goat-anti-rabbit immunoglobulin G's. The enzyme can first be visualized after 3 days of seedling growth and is associated with small foci within the cytoplasm of the storage parenchyma cells farthest from the vascular bundles. On the 4th day of growth, the protease is also present in the numerous large protein bodies within these cells. Vicilin peptidohydrolase is known to be synthesized de novo starting on the 3rd day of growth. Our observations are therefore consistent with the interpretation that the enzyme is synthesized in the cytoplasm and subsequently transported to the protein bodies.

Cytoplasm↗
PubMed1979

RNA metabolism and membrane-bound polysomes in relation to globulin biosynthesis in cotyledons of developing field beans (Vicia faba L.).

In cotyledon cells of developing field beans the RNA content per cell does not change in the second half of developmental period 2, whereas globulin biosynthesis continues. The constant RNA content per cell results from an equilibrium between RNA synthesis and degradation. All types of RNA are synthesized until the end of globulin biosynthesis, but poly(A)-containing RNA was preferentially labelled during maximum globulin formation. During stage 2 of seed development of poly(A)-containing RNA fraction represents a discrete peak in the 12--18-S region on agarose gels and corresponds to the peak of poly(A)-containing RNA isolated from polysomes. alpha-Amanitin inhibits selectively the labelling of poly(A)-containing RNA and concomitantly globulin formation. Translation of total poly(A)-containing RNA, free and membrane-bound polysomes in a cell-free wheat germs demonstrates that the globulins are preferentially produced on membrane-bound polysomes and that poly(A)-containing RNA includes the mRNA for both vicilin and legumin.

Amanitins↗
PubMed1976

Ultrastructural studies of the placenta of the ewe: phagocytosis of erythrocytes by the chorionic epithelium at the central depression of the cotyledon.

Extravasated maternal blood, which escapes from capillaries and larger blood vessels within the tips of the maternal septa, is responsible for the characteristic pigmentation of the central depression of the ovine cotyledon in the last third of pregnancy. The chorionic epithelium of this region is actively engaged in the uptake and subsequent breakdown of maternal erythrocytes, which may represent an important source of iron for the foetus during the period of maximum intra-uterine growth.

Animals↗
PubMed1977

Characteristics of potassium ion transport in pea cotyledon mitochondria isolated by a zonal technique.

Methodology was developed for measurement of K+ transport in pea cotyledon mitochondria isolated by zonal centrifugation. The valinomycin-mediated transport process required respiratory energy from Krebs cycle intermediates and was completely reversible in the absence of oxygen. The rate and extent of uptake were dependent on the presence of proton-conducting anions (with acetate plus phosphate being most effective), well-coupled mitochondria, and on the K+ concentration.

Biological Transport, Active↗
PubMed1977

Partial characterization of a soluble ATPase from pea cotyledon mitochondria.

A partially purified soluble ATPase (ATP phosphohydrolase, EC 3.6.1.3) from pea cotyledon mitochondria was characterized. Inhibition patterns with azide, NaF, and cold, and a stimulation by 2,4-dinitrophenol were typical of F1-ATPases from mammalian mitochondria. The enzyme hydrolysed GTP, ITP, and ATP, but not CTP, UTP, ADP, or IDP. ATPase and ITPase activities were strongly inhibited by ADP and to a lesser extent by IDP. Distinctive properties of the pea mitochondrial enzyme were activation by high concentrations of CaCl2 and stimulation by NaCl.

Adenosine Diphosphate↗
PubMed1979

Studies on isocitrate lyase isolated from Lupinus cotyledons.

Isocitrate lyase (threo-DS-isocitrate glyoxylate-lyase, EC 4.1.3.1) was isolated from cotyledons of Lupinus seedlings, purified 100-fold with respect to its initial specific activity and characterized (Km, pH optimum, Mg2+ requirement, sulfhydryl inhibitors, and synthase activity). The final purified preparation consisted of two homogeneous protein bands clearly separated by electrophoresis on polyacrylamide gel and chromatography on Sephadex G 200. Reducing agents are necessary for the maintenance of enzyme activity. The most effective reducing agent studied was 1,4-dithioerythreitol. The effect of several metabolites (oxalate, malonate, phosphoenolpyruvate, succinate, malate, tartrate, gluconate-6-phosphate, sorbose, sorbitol, and inositol) on the activity of purified preparations was tested. Oxalate proved to be the strongest inhibitor, seconded closely by phosphoenolpyruvate. The spectral characteristics of the purified enzyme are as follows: ultraviolet peak at 280 nm and fluorescence peak at 340 nm. The solid state infrared spectrum of the enzyme (lyophilized) showed that the enzyme was mostly in the alpha-helix conformation with very slight random orientation.

Chloromercuribenzoates↗
PubMed1975

Localization of lectins in legume cotyledons.

High-resolution techniques for the localization of lectins are described. Concanavalin A (Con A) and phytohaemagglutinin (PHA) are localized using a fluorescent method with (FITC)-labelled immunoglobulins which bind to the lectins in sections of jack and red kidney bean cotyledons. Specificity is defined by the use of specific sugar inhibitors. Both Con A and PHA are found in cytoplasmic sites. Lectins with beta-glycoside specificity are detected with red-coloured artificial carbohydrate antigens. The beta-galactosyl and beta-glucosyl antigens bind specifically to clusters of spherical bodies in the intercellular spaces, to cell wall sites, and to the periphery of the cytoplasm associated with the cell membrane.

Cell Wall↗
PubMed1977

Immunofluorescent localization of urease in the cotyledons of jack bean, Canavalia ensiformis.

Urease has been localized in sections of cotyledons from germinating seeds of jack bean, using FITC-labelled immunoglobulin prepared from urease antiserum raised in rabbits. The complication of lectin binding to the immunoglobulins was resolved by treatment of the sections with specific glycosides. Urease is localized in 2 sites: within the cytoplasm of storage parenchyma cells in spherical granules up to 3 micrometer in diameter, and within the intercellular spaces in spherical granules. Although similar in size, the latter are distinguished from the cytoplasmic granules by the presence of beta-lectin and appear to function as an extracellular lytic compartment or lysosome.

Antibody Specificity↗
PubMed1992

Time-dependent inhibition of pea cotyledon diamine oxidase by some hydrazides.

The inhibition of diamine oxidase (EC 1.4.3.6) from pea cotyledons (PDAO) by some hydrazides has been studied. It was found that PDAO is inhibited in a time-dependent manner at pH = 7.0 by the hydrazides of acetic, benzoic, nicotinic, isonicotinic, picolinic and 3,4-dihydro-4-oxophtalazine-1-carboxylic acids, by 1-(carboxymethyl)trimethylammonium chloride hydrazide (Girard's reagent T), 1-(carboxymethyl)pyridinium chloride hydrazide (Girard's reagent P) and oxalic acid dihydrazide. The inhibition was partially reversible. Rate constants for enzyme inactivation were in the range 0.29-1.95 min-1. The hydrazides give apparent noncompetitive inhibition at pH = 7.0, but for isonicotinic hydrazide, this changes to competitive inhibition at pH = 8.0. Apparent inhibition constants (K1APP) for the hydrazides with PDAO are in the range 0.005-1.5 mmol l-1.

Amine Oxidase (Copper-Containing)↗
PubMed1977

Transmission of alfalfa mosaic virus through Nicandra physaloides seeds and its localization in embryo cotyledons.

Alfalfa mosaic virus (AMV) was found to be transmitted through seeds of Nicandra physaloids L. The average seed transmission rate of the AMV isolates T6, LMBG-4 and ST amounted to 23, 4 and 0 per cent, repectively. In the cytoplasm of parenchyma cells of embryo cotyledons of seeds from plants infected with the T6 isolate, electron microscopy revealed AMV aggregates of type 2A and aggregations of irregularly viral particles with a tendency to subparallel alignment, representing early stages of type 2A aggregates.

Cytoplasm↗