scholarly journals Solubilization and partial characterization of rat epididymal Δ 4-steroid 5 α-reductase (cholestenone 5 α-reductase)

1983 ◽  
Vol 211 (1) ◽  
pp. 65-74 ◽  
Author(s):  
H Scheer ◽  
B Robaire
Keyword(s):  
Reductase Activity ◽  
Sedimentation Coefficient ◽  
Molecular Size ◽  
Enzymic Activity ◽  
Subcellular Fractions ◽  
Biologically Active ◽  
Stable Form ◽  
Membrane Bound ◽  
Relative Capacity

Epididymal delta 4-steroid 5 alpha-reductase (cholestenone 5 alpha-reductase), the enzyme that catalyses the conversion of testosterone into the biologically active metabolite dihydrotestosterone (17 beta-hydroxy-5 alpha-androstan-3-one), is a membrane-bound enzyme found in both nuclear and microsomal subcellular fractions. In order to characterize epididymal delta 4-steroid 5 alpha-reductase, it was first necessary to solubilize the enzymic activity. Of the various treatments tested, a combination of 0.5% (w/v) Lubrol WX, 0.1 M-sodium citrate and 0.1 M-KCl maintained enzymic activity at control values and solubilized 66% of total epididymal delta 4-steroid 5 alpha-reductase activity in an active and stable form. The sedimentation coefficient of solubilized delta 4-steroid 5 alpha-reductase, as determined in continuous sucrose density gradients, was greater for the microsomal than for the nuclear enzyme (11.6S compared with 10.1S). Although the apparent Km values of the enzyme for testosterone were similar in nuclear and microsomal subcellular fractions (range 1.75 × 10(-7) × 4.52 × 10(-7)M), the apparent Km of the enzyme for NADPH was about 30-fold greater for the microsomal enzyme than for the nuclear enzyme. The apparent Km of the enzyme for either substrate was not significantly altered after solubilization. The relative capacity of steroids to inhibit the enzymic activity, the pH optima and the effects of Ca2+ and Mg2+ were similar for membrane-bound and solubilized delta 4-steroid 5 alpha-reductase in both the nuclear and the microsomal fractions. The results reported demonstrate that epididymal delta 4-steroid 5 alpha-reductase can be solubilized in an active and stable form with no significant changes in the kinetic characteristics of the enzyme after solubilization; furthermore, kinetic and molecular-size differences observed for the nuclear and the microsomal forms of the enzyme suggest that there may exist at least two forms of epididymal delta 4-steroid 5 alpha-reductase.

Immunochemical and biological characterization of calcitonin originating from transplanted medullary thyroid carcinoma in rats

1982 ◽  
Vol 99 (3) ◽  
pp. 397-403 ◽  
Author(s):  
Lisbeth Myhre ◽  
Arne Ekeland ◽  
Kaare M. Gautvik
Keyword(s):  
Biological Activities ◽  
Gel Filtration ◽  
Molecular Size ◽  
Serum Levels ◽  
Biologically Active ◽  
Subcutaneous Injections ◽  
Medullary Thyroid ◽  
Biological Potency ◽  
Medullary Thyroid Carcinomas

Abstract. The immunoreactive and biological activities of calcitonin (CT) produced by transplanted rat medullary thyroid carcinomas (MCT) have been studied. Immunoreactive CT (iCT) in serum and in MCT tissues of rats carrying tumours of generations 5–8 was characterized by gel filtration on Sephadex G-100 followed by radioimmunological measurements using region specific antiserum. The hypocalcaemic effect of sera and tumour extracts was tested in a rat bioassay. Rats with transplanted MCT of the 5th and 6th generations had mainly (70–84%) circulating iCT species of molecular size comparable to intact hormone. However, in rats with tumours of the 7th and 8th generations corresponding circulating iCT forms comprised less than 52% of total immunoreactivity while 32–38% eluted earlier. In conparison, iCT corresponding to intact hormone represented 30–50% of total immunoreactivity in the tumour extracts and no differences were observed between the generations. Subcutaneous injections of sera from MCT rats and of tumour extracts reduced the serum levels of ionized calcium in test rats. The sera containing mainly intact iCT showed the strongest biological potency. We conclude that rat MCT transplanted under the kidney capsule is able to secrete biologically active CT. However, the heterogeneity of circulating iCT increases in rats with transplanted tumours of older generations, approaching the heterogeneity of stored hormone in the gland.

scholarly journals Characterization of the membrane-bound nitrate reductase activity of aerobically grown chlorate-sensitive mutants of escherichia coli K12

FEBS Letters ◽  
1978 ◽  
Vol 95 (2) ◽  
pp. 290-294 ◽  
Author(s):  
Gérard Giordano ◽  
Alec Graham ◽  
David H. Boxer ◽  
Bruce A. Haddock ◽  
Edgard Azoulay
Keyword(s):  
Escherichia Coli ◽  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Escherichia Coli K12 ◽  
Membrane Bound

Characterization of photosystem II with the atomic-force microscope

1992 ◽  
Vol 50 (2) ◽  
pp. 1146-1147
Author(s):  
Kathleen M. Marr ◽  
Mary K. Lyon
Keyword(s):  
Photosystem Ii ◽  
Atomic Force Microscope ◽  
Three Dimensional ◽  
Biologically Active ◽  
Atomic Force ◽  
Freeze Etching ◽  
Image Averaging ◽  
Oxygen Evolving ◽  
Averaging Techniques

Photosystem II (PSII) is different from all other reaction centers in that it splits water to evolve oxygen and hydrogen ions. This unique ability to evolve oxygen is partly due to three oxygen evolving polypeptides (OEPs) associated with the PSII complex. Freeze etching on grana derived insideout membranes revealed that the OEPs contribute to the observed tetrameric nature of the PSIl particle; when the OEPs are removed, a distinct dimer emerges. Thus, the surface of the PSII complex changes dramatically upon removal of these polypeptides. The atomic force microscope (AFM) is ideal for examining surface topography. The instrument provides a topographical view of individual PSII complexes, giving relatively high resolution three-dimensional information without image averaging techniques. In addition, the use of a fluid cell allows a biologically active sample to be maintained under fully hydrated and physiologically buffered conditions. The OEPs associated with PSII may be sequentially removed, thereby changing the surface of the complex by one polypeptide at a time.

Characterization of Biologically Active Substances from Calendula officinalis

2018 ◽  
Vol 18 (14) ◽  
pp. 1167-1174 ◽  
Author(s):  
Petra Lovecka ◽  
Jan Lipov ◽  
Kamila Thumova ◽  
Anna Macurkova
Keyword(s):  
Biologically Active Substances ◽  
Biologically Active ◽  
Calendula Officinalis ◽  
Active Substances

Ferrous materials degradation: characterisation of rust by colour – an overview

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Desmond E. P. Klenam ◽  
Michael O. Bodunrin ◽  
Stefania Akromah ◽  
Emmanuel Gikunoo ◽  
Anthony Andrews ◽  
...  
Keyword(s):  
Yellow Rust ◽  
Brown Rust ◽  
Future Research ◽  
Stable Form ◽  
Low Oxygen ◽  
High Moisture ◽  
Oxygen Environment ◽  
Causative Factors ◽  
Analytical Tools

Abstract An overview of the characterisation of rust by colour is presented. Each distinct rust colour is caused by atmospheric impurities, high or low moisture content and high or low oxygen environment over time. Yellow rust is mainly due to the high moisture environment over a period of time, which drips. Brown rust is dry, crusty and due to water and oxygen contact with localised patches on component surfaces. Black rust, the most stable form, occurs in low moisture and low oxygen environment. The rust residue shows where the reaction started, especially in contact with chlorides. The causative factors of red rust are atmospheric and similar to black rust in a chloride-containing environment. The effect of packaging, manufacturing and environmental factors on rust colour is briefly discussed. Visual characterization of rust could pre-empt root causes and analytical tools for validation. The limitations of these concepts are mentioned and directions for future research highlighted.

scholarly journals Unravelling the Skin Secretion Peptides of the Gliding Leaf Frog, Agalychnis spurrelli (Hylidae)

Biomolecules ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 667 ◽  
Author(s):  
Carolina Proaño-Bolaños ◽  
Ailín Blasco-Zúñiga ◽  
José Rafael Almeida ◽  
Lei Wang ◽  
Miguel Angel Llumiquinga ◽  
...  
Keyword(s):  
Inhibitory Concentration ◽  
Structural Diversity ◽  
Biologically Active ◽  
Biological Characterization ◽  
Skin Secretion ◽  
Peptide Profile ◽  
Active Chemical ◽  
Molecular Masses ◽  
Skin Secretions

Frog skin secretions contain medically-valuable molecules, which are useful for the discovery of new biopharmaceuticals. The peptide profile of the skin secretion of Agalychnis spurrelli has not been investigated; therefore, the structural and biological characterization of its compounds signify an inestimable opportunity to acquire new biologically-active chemical scaffolds. In this work, skin secretion from this amphibian was analysed by molecular cloning and tandem mass spectrometry. Although the extent of this work was not exhaustive, eleven skin secretion peptides belonging to five peptide families were identified. Among these, we report the occurrence of two phyllokinins, and one medusin-SP which were previously reported in other related species. In addition, eight novel peptides were identified, including four dermaseptins, DRS-SP2 to DRS-SP5, one phylloseptin-SP1, and three orphan peptides. Phylloseptin-SP1 and dermaseptins-SP2 were identified in HPLC fractions based on their molecular masses determined by MALDI-TOF MS. Among the antimicrobial peptides, dermaseptin-SP2 was the most potent, inhibiting Escherichia coli, Staphylococcus aureus, and ORSA with a minimum inhibitory concentration (MIC) of 2.68 μM, and Candida albicans with an MIC of 10.71 μM, without haemolytic effects. The peptides described in this study represent but a superficial glance at the considerable structural diversity of bioactive peptides produced in the skin secretion of A. spurrelli.

scholarly journals Isolation and characterization of a membrane protein from rat erythrocytes which inhibits lysis by the membrane attack complex of rat complement

1992 ◽  
Vol 284 (1) ◽  
pp. 169-176 ◽  
Author(s):  
T R Hughes ◽  
S J Piddlesden ◽  
J D Williams ◽  
R A Harrison ◽  
B P Morgan
Keyword(s):  
Affinity Purification ◽  
Membrane Attack Complex ◽  
Erythrocyte Membranes ◽  
Dependent Manner ◽  
Inhibitory Protein ◽  
Rat Erythrocytes ◽  
Butanol Extract ◽  
Isolation And Characterization ◽  
Membrane Bound

The membrane attack complex (MAC) of complement in humans is regulated by several membrane-bound proteins; however, no such proteins have so far been described in other species. Here we report the isolation and characterization of a rat erythrocyte membrane glycoprotein of molecular mass 21 kDa which inserts into cell membranes and is a potent inhibitor of the rat MAC. This protein, here called rat inhibitory protein (RIP), was first partially purified by column chromatography from a butanol extract of rat erythrocyte membranes. Monoclonal antibodies (Mabs) were raised against RIP and used for its affinity purification. Affinity-purified RIP was shown to inhibit in a dose-dependent manner the cobra venom factor (CVF)-mediated ‘reactive’ lysis of guinea pig erythrocytes by rat complement. Conversely, the anti-RIP MAbs 6D1 and TH9 were shown to markedly enhance the CVF-mediated lysis of rat erythrocytes by rat complement. RIP acted late in the assembly of the MAC (at or after the C5b-8 stage) and was releasable from the membranes of rat erythrocytes by phosphatidylinositol-specific phospholipase C. These features, together with its size, deglycosylation pattern and N-terminal amino acid sequence, lead us to conclude that RIP is the rat homologue of the human MAC-inhibitory protein CD59 antigen.

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