Brain alkaline phosphatase

Attempts were made to purify brain alkaline phosphatase (S5). 

A kinetic study on the activation of deoxyribonuclease I by magnesium has shown that the activation curve is biphasic (the substrate being the Mg salt of bovine spleen DNA). This indicates that activation occurs at two sites on the protein. Free Mg + was required for enzyme activity, confirming that a metallo-enzyme as well as a metallo-substrate is necessary for deoxyribonuclease I activity. In contrast, it has been shown that the pyrophosphatase activity of bovine brain alkaline phosphatase depends on Mg + bound to the enzyme but not on the formation of a magnesium-substrate complex. 

Hydrocephaly decreases in weight of brain, lung, liver, and kidney decreases in liver glycogen, kidney proteins and alkaline phosphatase and disrupted brain DNA and protein metabolism (Kav-lock et al. 1982)... 

Freshly isolated or subcultured brain microvascular endothelial cells offer a notable in vitro tool to study drug transport across the blood-brain barrier. Cells can be grown to monolayers on culture plates or permeable membrane supports. The cells retain the major characteristics of brain endothelial cells in vivo, such as the morphology, specific biochemical markers of the blood-brain barrier, and the intercellular tight junctional network. Examples of these markers are y-glutamyl transpeptidase, alkaline phosphatase, von-Willebrandt factor-related antigen, and ZO-1 tight junctional protein. The methods of... 

Numerous modifications of in vitro culture systems have been developed for the estimation of BBB transfer [52]. Culture systems in use are either primary cultures of brain microvessel endothelial cells (BMEC) or immortalized endothelial cell hues. BMEC may be grown in co-culture with astrocytes or in astrocyte-conditioned medium. Astrocyte-derived factors increase the tightness of the barrier as measured by transendothelial electrical resistance (TEER) and by the permeability of hydrophUic markers such as sucrose. They also up-regulate the expression of BBB-enriched enzymes such as y-glutamyl transpeptidase (y-GTP) and alkaline phosphatase. A setup of the in vitro technique in a transwell system for transport studies is depicted in Figure 2.5. 

Primary cultured porcine or bovine brain capillary endothelial cells have been used as an in vitro model for the BBB. Recently, an immortalized cell line has been established from mouse, rat, and human brain capillary endothelial cells by infection with Simian virus 40 or transfection of SV40 large T antigen (45 -7). Tatsuta et al. established an immortalized mouse brain capillary endothelial cell line (MBEC4). The activity of y-glutamyl transpeptidase and alkaline phosphatase, specific marker enzymes for brain capillary endothelial cells, was half that in the brain capillary (45). Also, P-gp was expressed on the apical membrane of MBEC4 cells, which corresponds to the abluminal membrane of the brain... 

The blood-brain barrier is a biochemical as well as a physical barrier. Brain endothelial cells create an enzymatic barrier composed of secreted proteases and nucleotidases, as well as intracellular metabolizing enzymes such as cytochrome P-450. Furthermore, y-glutamyl transpeptidase, alkaline phosphatase, and aromatic acid decarboxylase are more prevalent in cerebral microvessels than in nonneuronal capillaries. The efflux transporter P-glycoprotein and other extrusion pumps are present on the membrane surface of endothelial cells, juxtaposed toward the interior of the capillary. Furthermore, CNS endothelial cells display a net negative charge at the interior of the capillaries and at the basement membrane. This provides an additional selective mechanism by impeding passage of anionic molecules across the membrane. 

Tissue uptake of vitamin Be is again by carrier-mediated diffusion of pyridoxal (and other unphosphorylated vitamers), followed by metabolic trapping by phosphorylation. Circulating pyridoxal and pyridoxamine phosphates are hydrolyzed by extracellular alkaline phosphatase. All tissues have pyridoxine kinase activity, but pyridoxine phosphate oxidase is found mainly in the liver, kidney, and brain. 

Catalan RE, Martinez AM, Aragones MD, Miguel BG, Robles A (1988) Insulin action on brain micro vessels effect on alkaline phosphatase. Biochem Biophys Res Commun 150 583-590. 

The co-administration of M. oleifera seed powder with arsenic protects animals from arsenic induced oxidative stress and reduce body arsenic burden (49). Exposure of rats to arsenie (2.5 mg/kg, intraperitoneally for 6 weeks) increases the levels of tissue reaetive oxygen species (ROS), metallothionein (MT) and thiobarbitnrie aeid reaetive substance (TEARS) and is accompanied by a decrease in the aetivities in the antioxidant enzymes such as superoxide dismutase (SOD), eatalase and glutathione peroxidase (GPx). Also, Arsenic exposed mice exhibits hver injury as reflected by reduced acid phosphatase (AGP), alkaline phosphatase (ALP) and aspartate aminotransferase (AST) activities and altered heme synthesis pathway as shown by inhibited blood 8-aminolevulinic acid dehydratase (5-ALAD) activity. Co-administration of M. oleifera seed powder (250 and 500 mg/kg, orally) with arsenie significantly increases the activities of SOD, catalase, GPx with elevation in redueed GSH level in tissues (liver, kidney and brain). These ehanges are accompanied by approximately 57%, 64% and 17% decrease in blood ROS, liver metallothionein (MT) and lipid peroxidation respectively in animal eo-administered with M. oleifera and arsenic. There is a reduced uptake of arsenie in soft tissues (55% in blood, 65% in liver, 54% in kidneys and 34% in brain) following eo-administration of M. oleifera seed powder (particularly at the dose of 500 mg/kg). This points to the fact that administration of M. oleifera seed powder could be beneficial during chelation therapy with a thiol chelator (26). 

Roux, F., Durieu-Trautmann, O Chaverot, N., Claire, M., Mailly, P., Bourre, J.M., Strosberg, A.D., and Couraud, P.O. (1994) Regulation of gamma-glutamyl transpeptidase and alkaline phosphatase activities in immortalized rat brain microvessel endothelial cells. Journal of Cellular Physiology, 159, 101-113. 

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