Selenoprotein P is an extracellular protein containing presumably 10 selenocysteines that are encoded by the UGA stop codon in the open reading frame of the mRNA. The function of selenoprotein P is currently unknown, although several indirect lines of evidence suggest that selenoprotein P is a free radical scavenger. We first developed a conventional procedure to isolate selenoprotein P from human plasma. Next, we investigated the reactivities of selenoprotein P against various hydroperoxides in the presence of glutathione. Although selenoprotein P reduces neither hydrogen peroxide nor tertiary butyl hydroperoxide, it does reduce phospholipid hydroperoxide such as 1-palmitoyl-2-(13-hydroperoxy-cis-9,trans-11-octadecadienoyl)-3-phosphatidylcholine hydroperoxide. Kinetic analysis demonstrated a tert-uni ping-pong mechanism, similar to those described for classical glutathione peroxidase and phospholipid hydroperoxide glutathione peroxidase. Not only glutathione, but also dithiothreitol, mercaptoethanol, cysteine, and homocysteine, were effective as reducing substances, as in the case of phospholipid hydroperoxide glutathione peroxidase. These results show that selenoprotein P functions as a phospholipid hydroperoxide glutathione peroxidase in extracellular fluids.
Integrated image-based design and solid free-form fabrication can create scaffolds that attain desired elasticity and permeability while fitting any 3D craniofacial defect. The scaffolds could be manufactured from degradable polymers, calcium phosphate ceramics and titanium. The designed scaffolds supported significant bone regeneration for all pore sizes ranging from 300 to 1200 microns. These results suggest that designed scaffolds are clinically applicable for complex craniofacial reconstruction.
~~ ~Aldehyde oxidase (AO; EC 1.2.3.1) that could oxidize indole-3-acetaldehyde into indole-3-acetic acid was purified approximately 2000-fold from coleoptiles of 3-d-old maize (Zea mays 1.) seedlings. The apparent molecular mass of the native enzyme was about 300 kD as estimated by gel-filtration column chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the enzyme was composed of 150-kD subunits. It contained flavin adenine dinucleotide, iron, and molybdenum as prosthetic groups and had absorption peaks in the visible region (300-600 nm). To our knowledge, this is the first demonstration of the presence of flavin adenine dinucleotide and metals i n plant AO. Other aromatic aldehydes such as indole-3-aldehyde and benzaldehyde also served as good substrates, but N-methylnicotinamide, a good substrate for animal AO, was not oxidized. 2-Mercaptoethanol, p-chloromercuribenzoate, and iodoacetate partially inhibited the activity, but well-known inhibitors of animal AO, such as menadione and estradiol, caused no reduction in activity. These results indicate that, although maize AO is similar to animal enzymes in molecular mass and cofactor components, it differs i n substrate specificity and susceptibility t o inhibitors. lmmunoblotting analysis with mouse polyclonal antibodies raised against the purified maize AO showed that the enzyme was relatively rich i n the apical region of maize coleoptiles. The possible role of this enzyme is discussed in relation to phytohormone biosynthesis in plants.AO (EC 1.2.3.1) has been extensively investigated in animals and microorganisms. The enzyme catalyzes the oxidation of a variety of aldehydes and N,-containing heterocycles in the presence of.0, or certain redox dyes (Rajagopalan and Handler, 1966; Hall and Krenitsky, 1986). The enzyme has also been reported to reduce diphenyl sulfoxides (Yoshihara and Tatsumi, 1986), aromatic heterocyclic compounds (Bauer and Howard, 1991), and oximes (Tatsumi and Ishigai, 1987). AO is similar t o xanthine dehydrogenase (oxidase) in being a multicomponent enzyme that contains a molybdenum cofactor, nonheme iron, and FAD as prosthetic groups. The enzyme is found in the small intestine and liver of animals and has been implicated in the detoxification of various xenobiotics, including certain cancer chemotherapeutic agents (Bauer and Howard, 1991;Stoddart and Levine, 1992; Hirao et al., 1994). The enzyme may also play a role in retinoic acid synthesis (Tomita et al., 1993; Huang and Ichikawa, 1994) and in the degradation of aromatic aldehydes formed as a result of lignin breakdown by a soil bacterium (Crawford et al., 1982) and snails (Large and Connock, 1994).However, in plants only a limited amount of information has been published concerning this enzyme, including studies of Auena coleoptiles (Rajagopal, 1971), potato tubers (Rothe, 1974), cucumber seedlings (Bower et al., 1978), and pea seedlings (Miyata et al., 1981). Much attention has been focused on this enzyme because of its possible involvement ...
Current bone tissue engineering strategies aim to grow a tissue similar to native bone by combining cells and biologically active molecules with a scaffold material. In this study, a macroporous scaffold made from the seaweed-derived polymer alginate was synthesized and mineralized for cell-based bone tissue engineering applications. Nucleation of a bone-like hydroxyapatite mineral was achieved by incubating the scaffold in modified simulated body fluids (mSBF) for four weeks. Analysis using scanning electron microscopy and energy dispersive x-ray analysis indicated growth of a continuous layer of mineral primarily composed of calcium and phosphorous. X-ray diffraction analysis showed peaks associated with hydroxyapatite, the major inorganic constituent of human bone tissue. In addition to the mineral characterization, the ability to control nucleation on the surface, into the bulk of the material, or on the inner pore surfaces of scaffolds was demonstrated. Finally, human MSCs attached and proliferated on the mineralized scaffolds and cell attachment improved when seeding cells on mineral coated alginate scaffolds. This novel alginate- HAP composite material could be used in bone tissue engineering as a scaffold material to deliver cells, and perhaps also biologically active molecules.
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