Biomedical subjects
Publications and source records attributed to R Got.
Rat liver microsomal membranes have been shown to contain an UDP-glucose binding protein. Its mol. wt was estimated to be 120 000 by gel filtration and by ultracentrifugation in a sucrose gradient. The receptor activity was purified by gel filtration on Sephadex G200 and analysed by gel-electrofocusing.
Explore the source record for details and available documents.
Rat liver microsomal membranes have been shown to contain a biosynthetic pathway of UDP-glucose. In addition, they are able to bind UDP-glucose in a reversible manner, As UDP-glucose is also metabolized in these membranes, the study of the binding has been performed with a microsomal Triton X 100 extract. This reversible binding depends on pH (maximum at pH 8.1) and manganous ions, and disappears at pH 6.5. It exhibits a high affinity (K-diss equals 3 mu M), and a narrow specifity for UDP-glucose. Proteolytic digestion inhibits the binding up to 90%, showing that the UDP-glucose receptor has a proteic nature. These binding characteristics have been also found in the membranes themselves, indicating that the detergent solubilization does not destroy the protein binding capacity.
Explore the source record for details and available documents.
Microsomal preparations from rat liver mediate transfer of glucosyl units from UDP-glucose to three different kinds of acceptors: an endogenous glycoprotein, exogenous glycogen and collagen. Both glucosyl transferases work at acidic pH, 6.5 for transfer on endogeneous acceptor and glycogen and at pH 5.5 for transfer on collagen. None of these enzymes require divalent cations for activity. While transfers on endogenous acceptor and glycogen are inhibited by the presence of a non-ionic detergent, Triton X-100, the transfer on collagen is activated by the same detergent. Glycogen-synthase activity requires glucose 6-phosphate at an optimal concentration of 1 mM. The Km values for UDP-glucose are respectively: 0.5 mM, 0.33 mM, and 1 mM for transfer on endogenous acceptor, glycogen and collagen. Characterisation of the product indicates that a protein-bound alpha1-4 glucan is formed when no primer is added. Enzymatic and acidic hydrolyses of radioactive glycogen and collagen show only glucose as a radioactive sugar identified by thin layer chromatography on cellulose. Pre-treatment of microsomal membranes by alpha-amylase demonstrates that glucosyltransferases are not adsorbed on endogenous glycogen and seem to be really membranous enzymes.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
We report here the presence in human milk fat globules membranes of 5'-nucleotidase, Na(+)-K(+) and Mg(2+) ATPases, and phosphodiesterase which are marker enzymes for the plasma membrane. Thiamine-pyrophosphatase, lactose and lactosamine synthetase were also found, which are usually considered as Golgi apparatus marker enzymes. Lastly, glucose-6-phosphatase, NADH-cytochrome c reductase and RNase, characteristic enzymes of the endoplasmic membrane, were also present.
Explore the source record for details and available documents.
Explore the source record for details and available documents.