Membrane-Bound Enzymic Activity in the Base-Exchange Reactions of Phospholipid Metabolism

1971 ◽  
pp. 111-134 ◽  
Author(s):  
G. Porcellati ◽  
F. di Jeso
Keyword(s):  
Phospholipid Metabolism ◽  
Enzymic Activity ◽  
Exchange Reactions ◽  
Base Exchange ◽  
Membrane Bound

Membrane-Bound Base-Exchange Reactions in Animal Tissues

1978 ◽  
pp. 287-299 ◽  
Author(s):  
Giuseppe Porcellati ◽  
Alberto Gaiti ◽  
Helmut Woelk ◽  
Gianna Evelina de Medio ◽  
Marina Brunetti ◽  
...  
Keyword(s):  
Exchange Reactions ◽  
Animal Tissues ◽  
Base Exchange ◽  
Membrane Bound

A Study on the Possible Occurrence of Base-Exchange Reactions in Vivo

1978 ◽  
pp. 319-325 ◽  
Author(s):  
P. Orlando ◽  
G. Arienti ◽  
P. Saracino ◽  
L. Corazzi ◽  
P. Massari ◽  
...  
Keyword(s):  
Exchange Reactions ◽  
Base Exchange

Possible involvement of the base exchange enzymes in the phospholipid metabolism in LAN-2 cells

1993 ◽  
Vol 14 (3) ◽  
pp. 245-249
Author(s):  
G. Sorrentino ◽  
I. N. Singh ◽  
R. Massarelli ◽  
J. N. Kanfer ◽  
V. Bonavita
Keyword(s):  
Phospholipid Metabolism ◽  
Base Exchange

scholarly journals THE INTERACTION OF CATIONIC LIPOSOMES CONTAINING ENTRAPPED HORSERADISH PEROXIDASE WITH CELLS IN CULTURE

1974 ◽  
Vol 63 (2) ◽  
pp. 492-504 ◽  
Author(s):  
Wayne E. Magee ◽  
Charles W. Goff ◽  
Jean Schoknecht ◽  
M. Diane Smith ◽  
K. Cherian
Keyword(s):  
Cell Membrane ◽  
Horseradish Peroxidase ◽  
Hela Cells ◽  
Cationic Liposomes ◽  
Enzymic Activity ◽  
Positive Staining ◽  
Staining Reaction ◽  
Cytoplasmic Inclusions ◽  
Membrane Bound ◽  
Stable Particles

Cationic liposomes composed of sphingomyelin, cholesterol, and stearylamine were prepared with horseradish peroxidase trapped inside. Stable particles were formed in which 10–12% of the enzymic activity appeared to be located at, or near, the outer surface of the liposome. Adsorption and uptake of liposomes by HeLa cells were followed cytochemically by electron microscopy and quantitated by enzyme assay and by the distribution and fate of particles labeled with [14C]cholesterol and [125I]horseradish peroxidase. The particles were adsorbed by HeLa cells at least 300 times as efficiently as was free horseradish peroxidase. Many of the particles remained at the cell surface, but numerous membrane-bound cytoplasmic inclusions were observed to contain peroxidase-staining material. In addition, many areas of the cell membrane gave a positive staining reaction. It was concluded that many particles (presumably the larger ones) did not gain access to the interior of the cells, many were phagocytized, and some enzyme was transferred to the cell membrane, perhaps as a result of fusion of the liposomal membrane with the cell membrane.

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.

scholarly journals Hydrochemical characterization of shallow and deep groundwater in Basement Complex areas of southern Kebbi State, Sokoto Basin, Nigeria

2019 ◽  
Vol 9 (8) ◽  
Author(s):  
Saadu Umar Wali ◽  
Kabiru Jega Umar ◽  
Sheikh Danjuma Abubakar ◽  
Ifatokun Paul Ifabiyi ◽  
Ibrahim Mustapha Dankani ◽  
...  
Keyword(s):  
Water Samples ◽  
Shallow Groundwater ◽  
National Standard ◽  
World Health ◽  
Physical Parameters ◽  
Exchange Reactions ◽  
Basement Complex ◽  
Deep Groundwater ◽  
Base Exchange ◽  
Significant Difference

Abstract Groundwater under Basement Complex areas of southern Kebbi has been characterized in order to determine its suitability for drinking and irrigation use. Water samples were drawn from shallow groundwater (hand-dug shallow wells < 5 m) and deep groundwater (boreholes > 40 m). Physical parameters (i.e., temperature, TDS, pH, and EC), were determined in situ, using handheld meters. Discrete water samples were obtained for determination of chemical parameters. Results from several-sample ANOVA (Kruskal–Wallis test) suggested that heterogeneity in water table appeared to exert significant influence on groundwater chemistry which is characterized by a significant difference in pH, EC TH, Na+, Zn2+, Mg2+, PO43−, Cl−, HCO3−, SO42−, and NO3− concentrations. Also, ions including Fe3+, Zn2+, Mg2+, Na+, PO43−, and SO42− are above World Health Organization (2011) and National Standard for Drinking Water Quality (2007) reference guidelines. Most of the groundwater sources are moderately hard. Groundwater classification based on chloride, EC, and TDS revealed water of excellent quality for all types of uses. However, groundwater classification based on nitrate pollution revealed water of poor quality. Rock mineral is the major mechanism controlling water chemistry, as revealed by the Gibbs model. Most of the water sources have positive Scholler index, indicative of overall base exchange reactions in the underlying aquifers. Such condition was well explained by Piper trilinear diagram, which revealed two types of faces: Ca–Mg–HCO3 and Ca–Mg–SO4–Cl. The HCA categorized wells into three groups according to their hydrogeochemical physiognomies. Despite the significant difference in ions concentration and chemical indices, groundwater composition is more influenced by rock weathering than anthropogenic inputs. Groundwater evaluation for irrigation use indicates a significant difference in SAR level which is related to poor permeability index in shallow groundwater. Higher values of Kelly’s index and magnesium adsorption ratio threatened groundwater suitability for irrigation use in the study area.

scholarly journals Endogenous phospholipid-substrates of base-exchange reactions in rabbit platelet membranes

1986 ◽  
Vol 40 ◽  
pp. 243
Author(s):  
Shigehiro Morikawa ◽  
Shinkichi Taniguchi ◽  
Hideo Mori ◽  
Kimio Fujii ◽  
Motokazu Fujiwara ◽  
...  
Keyword(s):  
Rabbit Platelet ◽  
Exchange Reactions ◽  
Base Exchange ◽  
Platelet Membranes
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