scholarly journals DEVELOPMENTAL STUDIES ON GLYOXYSOMES IN RICINUS ENDOSPERM

1970 ◽  
Vol 44 (1) ◽  
pp. 94-102 ◽  
Author(s):  
B. P. Gerhardt ◽  
Harry Beevers
Keyword(s):  
Enzyme Activities ◽  
Isocitrate Lyase ◽  
Total Activity ◽  
Early Growth ◽  
Soluble Form ◽  
Synthetase Activity ◽  
Developmental Studies ◽  
Lyase Activity ◽  
Specific Activities

The development of glyoxysomes and their associated enzymes, isocitrate lyase and malate synthetase, was studied in the endosperm of castor bean seeds during germination and early growth in darkness. The protein content of the glyoxysome fraction, separated by sucrose density centrifugation, increased linearly from day 2 to day 4 and declined subsequently, while maximum enzyme activities were reached at day 5. The specific activities of the enzymes in the glyoxysomes increased until day 5 and remained constant thereafter. At all stages of germination the only organelle with isocitrate lyase activity was the glyoxysome, but at the earlier stages a greater portion of the total activity was recovered in the soluble form. Malate synthetase was found primarily in the glyoxysomes after day 4, but at earlier stages part of the activity appeared at regions of lower density on the sucrose gradient. It was shown that this particulate malate synthetase activity was due to glyoxysomes broken during preparation, and that, as a result of this breakage, isocitrate lyase was solubilized. We conclude that both enzymes are housed in the glyoxysome in vivo throughout the germination period, and that the rise and fall in enzyme activities in phase with fat breakdown correspond to the net production and destruction of this organelle.

scholarly journals RegA Plays a Key Role in Oxygen-Dependent Establishment of Persistence and in Isocitrate Lyase Activity, a Critical Determinant of In vivo Brucella suis Pathogenicity

2017 ◽  
Vol 7 ◽  
Author(s):  
Elias Abdou ◽  
María P. Jiménez de Bagüés ◽  
Ignacio Martínez-Abadía ◽  
Safia Ouahrani-Bettache ◽  
Véronique Pantesco ◽  
...  
Keyword(s):  
Isocitrate Lyase ◽  
Critical Determinant ◽  
Brucella Suis ◽  
Lyase Activity

Photo-induction sexuée du pyrénomycète Nectria galligena: influence de la mycosporine sur le rapport des activités NADPM+-socitrate déshydrogénase/isocitrate lyase

1989 ◽  
Vol 67 (2) ◽  
pp. 447-450 ◽  
Author(s):  
B. Dehorter ◽  
L. Lacoste
Keyword(s):  
Isocitrate Dehydrogenase ◽  
Isocitrate Lyase ◽  
Tricarboxylic Acid Cycle ◽  
Glyoxylate Cycle ◽  
Nectria Galligena ◽  
Lyase Activity ◽  
Growth Of Fungi ◽  
The Glyoxylate Cycle

The activity of two enzymes of the tricarboxylic acid cycle (NADP+-isocitrate dehydrogenase, EC 1.1.1.42) and the glyoxylate cycle (isocitrate lyase, EC 4.1.3.1) were assayed in vitro to determine the effects of darkness, light, and mycosporin (P310) on sexual morphogenesis in Nectria galligena Bres. In the absence of mycosporin, high isocitrate lyase activity was associated with vegetative growth of fungi kept in the dark. In contrast, light-induced perithecial development and mycosporin biosynthesis could be correlated with high ratios of isocitrate dehydrogenase to isocitrate lyase activity. This was confirmed by the fact that when mycosporin was added to the nutrient medium with incubation in darkness, the fertility of the fungus was partially expressed and the activity of isocitrate lyase was significantly reduced. Thus this enzyme would be repressed in vivo by mycosporin. Because of its photomimetic role in sexual differentiation and regulation of intermediate metabolism, mycosporin appears to be a biochemical transmitter of light energy required for the formation of ascocarps.

scholarly journals Biosynthesis of Cyanobacterial Phycobiliproteins in Escherichia coli: Chromophorylation Efficiency and Specificity of All Bilin Lyases from Synechococcus sp. Strain PCC 7002

2010 ◽  
Vol 76 (9) ◽  
pp. 2729-2739 ◽  
Author(s):  
Avijit Biswas ◽  
Yasmin M. Vasquez ◽  
Tierna M. Dragomani ◽  
Monica L. Kronfel ◽  
Shervonda R. Williams ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Biosynthetic Pathway ◽  
Expression System ◽  
Water Soluble ◽  
Soluble Form ◽  
Beta Subunits ◽  
Lyase Activity ◽  
Synechococcus Sp ◽  
Tetrapyrrole Chromophores

ABSTRACT Phycobiliproteins are water-soluble, light-harvesting proteins that are highly fluorescent due to linear tetrapyrrole chromophores, which makes them valuable as probes. Enzymes called bilin lyases usually attach these bilin chromophores to specific cysteine residues within the alpha and beta subunits via thioether linkages. A multiplasmid coexpression system was used to recreate the biosynthetic pathway for phycobiliproteins from the cyanobacterium Synechococcus sp. strain PCC 7002 in Escherichia coli. This system efficiently produced chromophorylated allophycocyanin (ApcA/ApcB) and α-phycocyanin with holoprotein yields ranging from 3 to 12 mg liter−1 of culture. This heterologous expression system was used to demonstrate that the CpcS-I and CpcU proteins are both required to attach phycocyanobilin (PCB) to allophycocyanin subunits ApcD (αAP-B) and ApcF (β18). The N-terminal, allophycocyanin-like domain of ApcE (LCM 99) was produced in soluble form and was shown to have intrinsic bilin lyase activity. Lastly, this in vivo system was used to evaluate the efficiency of the bilin lyases for production of β-phycocyanin.

Regulation of isocitrate metabolism in Chlamydomonas segnis

1977 ◽  
Vol 55 (16) ◽  
pp. 2178-2185 ◽  
Author(s):  
Samuel S. K. Foo ◽  
Samir S. Badour
Keyword(s):  
Isocitrate Dehydrogenase ◽  
Isocitrate Lyase ◽  
Nitrogen Deficiency ◽  
Competitive Inhibitor ◽  
Enzyme Preparations ◽  
Batch Cultures ◽  
Keto Acids ◽  
Effective Inhibition ◽  
Lyase Activity

Isocitrate lyase (EC 4.1.3.1) and isocitrate dehydrogenase (NADP+) (EC 1.1.1.42) activities were detected in cell-free extracts of Chlamydomonas segnis Ettl when the alga was grown photoautotrophically with 5% CO2 in air (v/v) at 11 klx. When the cultures were either bubbled with air (0.03% CO2), exposed to low light intensity (3 klx), or subjected to manganese or nitrogen deficiency, isocitrate lyase activity was undetectable. During growth in batch cultures provided with 5% CO2, the activity of the dehydrogenase was about 5–12 times greater than the lyase.Using partially purified (about 50-fold) enzyme preparations, isocitrate dehydrogenase (NADP+) showed greater affinity for isocitrate (Km = 0.008 mM) than did isocitrate lyase (Km = 0.1 mM). The dehydrogenase had Km values of 0.011 mM and 0.006 mM for NADP and Mn2+, respectively. Both enzymes were inhibited by α-ketoglutarate and oxalacetate at 1 mM, but the dehydrogenase was more sensitive to these two keto acids (68–79%) than the lyase (36%). Glycolate at 1 mM inhibited (36%) only the lyase, while glyoxylate had little effect. The dehydrogenase was subject to concerted inhibition by oxalacetate plus glyoxylate (Ki = 0.01 mM). This inhibition was competitive with respect to isocitrate, and preincubation of the enzyme with NADP in absence of isocitrate was necessary for effective inhibition. Each of NADPH (Ki = 0.06 mM) and ATP (Ki = 0.65 mM) was a non-competitive inhibitor (with respect to isocitrate) of isocitrate dehydrogenase (NADP+), and both nucleotides are suggested to be active in the in vivo regulation of isocitrate metabolism in C. segnis during photoautotrophy.

EFFECTS OF HEPARIN IN VIVO ON LYSOSOMAL ENZYMES IN RAT PLASMA

1967 ◽  
Vol 45 (7) ◽  
pp. 1145-1151 ◽  
Author(s):  
S. W. Levy
Keyword(s):  
Esterase Activity ◽  
Lysosomal Enzymes ◽  
Total Activity ◽  
Rat Plasma ◽  
Mechanisms Of Action ◽  
Specific Activities

Studies were carried out to determine the effects of heparin in vivo on acid ribonuclease, β-glucuronidase, acid β-glycerophosphatase, cathepsin, and several esterases in rat plasma. Increases occurred regularly in the specific activities of ribonuclease and β-glucuronidase, and inconsistently in that of acid β-glycerophosphatase. The activity of β-glucuronidase increased to a smaller extent in control animals. No change was observed in the activities of cathepsin or benzoylarginine ethyl esterase. Tributyrin esterase activity increased following the injection of heparin, the rise in total activity being due to an increase in the activities of both eserine-resistant and eserine-sensitive esterases in rat plasma. The results were discussed in terms of possible mechanisms of action of heparin and the significance of lysosomal enzymes in blood.

scholarly journals The distinction between γ-glutamylhydroxamate synthetase and l-glutamine–hydroxylamine glutamyltransferase activities in rat tissues. Studies in vivo

1973 ◽  
Vol 133 (1) ◽  
pp. 59-66 ◽  
Author(s):  
Annemarie Herzfeld ◽  
Nathan A. Estes
Keyword(s):  
Tissue Distribution ◽  
Enzyme Activities ◽  
Differential Response ◽  
Rat Tissues ◽  
Synthetase Activity ◽  
Assay Condition ◽  
Foetal Liver ◽  
Males And Females ◽  
Neonatal Kidney

The formation of γ-glutamylhydroxamate by homogenates under optimum assay condition showed an inconstancy in the ratios of the enzyme activities utilizing l-glutamate and ATP (γ-glutamylhydroxamate synthetase) and l-glutamine and ADP (l-glutamine–hydroxylamine glutamyltransferase) in a number of normal and neoplastic rat tissues. Although γ-glutamylhydroxamate synthetase activities in adult livers and kidneys were identical in males and females, l-glutamine–hydroxylamine glutamyltransferase activities in the organs of females were significantly lower. The developmental formations of the two activities in liver, kidney, brain and muscle were not simultaneous. The l-glutamine–hydroxylamine glutamyltransferase activity in foetal liver or neonatal kidney could be prematurely evoked by thyroxine, but the γ-glutamylhydroxamate synthetase activity remained unchanged. Injections of cortisol also had dissimilar effects on the two activities in thymus and hepatomas. The discrepant tissue distribution, asynchronous developmental formation and differential response to several hormonal stimuli provide evidence in vivo that the two activities are not catalysed by the same protein.

Changes in Adrenal Androgens and Steroidogenic Enzyme Activities From Ages 2, 4, to 6 Years: A Prospective Cohort Study

2020 ◽  
Vol 105 (10) ◽  
pp. 3265-3272 ◽  
Author(s):  
Jae Hyun Kim ◽  
Young Ah Lee ◽  
Youn-Hee Lim ◽  
Kyunghoon Lee ◽  
Bung-Nyun Kim ◽  
...  
Keyword(s):  
Early Childhood ◽  
Enzyme Activities ◽  
Morphological Changes ◽  
Steroidogenic Enzyme ◽  
Adrenal Androgens ◽  
Lyase Activity ◽  
Liquid Chromatography Tandem Mass ◽  
Z Scores ◽  
17 Hydroxyprogesterone

Abstract Context The levels of adrenal androgens are increased through the action of steroidogenic enzymes with morphological changes in the adrenal zona reticularis. Objective We investigated longitudinal changes in androgen levels and steroidogenic enzyme activities during early childhood. Design and Participants From a prospective children’s cohort, the Environment and Development of Children cohort, 114 boys and 86 girls with available blood samples from ages 2, 4, and 6 years were included. Outcome Measurements Serum concentrations of adrenal androgens using liquid chromatography-tandem mass spectrometry and steroidogenic enzyme activity calculated by the precursor/product ratio. Results During ages 2 to 4 years, 17,20-lyase and dehydroepiandrosterone (DHEA) sulfotransferase activities increased (P < 0.01 for both in boys). During ages 4 to 6 years, 17,20-lyase activity persistently increased, but 3β-hydroxysteroid dehydrogenase (HSD) and 17β-HSD activities decreased (P < 0.01 for all). Serum DHEA sulfate (DHEA-S) levels persistently increased from 2, 4, to 6 years, and DHEA, 17-hydroxyprogesterone, and androstenedione levels increased during ages 4 to 6 years (P < 0.01 for all). Serum DHEA-S levels during early childhood were associated with body mass index z-scores (P = 0.001 in only boys). Conclusion This study supports in vivo human evidence of increased 17,20-lyase and DHEA sulfotransferase activities and decreased 3β-HSD activity during early childhood.

Scanning Tunneling Microscopy and Atomic Force Microscopy of Enzymes and Enzyme Complexes

1990 ◽  
Vol 48 (3) ◽  
pp. 174-175
Author(s):  
Ronald D. Edstrom ◽  
Xiuru Yang ◽  
Mary E. Gurnack ◽  
Marcia A. Miller ◽  
Rui Yang ◽  
...  
Keyword(s):  
Cell Biology ◽  
Inorganic Ions ◽  
Bulk Liquid ◽  
Soluble Form ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Metabolic Channeling ◽  
Simplistic Notion ◽  
Soluble Enzymes

Many of the questions in biochemistry and cell biology are concerned with the relationships of proteins and other macromolecules in complex arrays which are responsible for carrying out metabolic sequences. The simplistic notion that the enzymes we isolate in soluble form from the cytoplasm were also soluble in vivo is being replaced by the concept that these enzymes occur in organized systems within the cell. In this newer view, the cytoplasm is organized and the “soluble enzymes” are in fact fixed in the cellular space and the only soluble components of the cell are small metabolites, inorganic ions etc. Further support for the concept of metabolic organization is provided by the evidence of metabolic channeling. It has been shown that for some metabolic pathways, the intermediates are not in free diffusion equilibrium with the bulk liquid in the cell but are passed along, more or less directly, from one enzyme to the next.

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