Immobilization of urease within a thin channel ultrafiltration cell

Urease [urea amidohydrolase, EC 3.5.1.5] has been immobilized within a thin channel ultrafiltration cell. Loss of enzymic activity as a result of concentration polarization and other causes was minimized. The flow characteristics of the reactor were fully characterized by analysis of the distribution of residence times (using F diagrams) and kinetic data were also obtained for the immobilized enzyme. These data show that under certain conditions the thin channel ultrafiltration reactor can be considered to be an ideally mixed vessel. After almost 8 days of continuous operation it was found that 15% of the original enzyme activity remained.     

Modification of functional arginine residues in purified bovine testicular hyaluronidase with butane-2, 3-dione

The effect of mononucleotides on the cytosolic rat liver glucocorticoid receptor has been studied by the use of aqueous dextran-poly(ethylene glycol) two-phase partitioning. During incubations in 0.4 M KCl at 0 degrees C, millimolar concentrations of ADP and ATP, but not AMP, CTP, UTP and GTP, inhibit the increase in the receptor partition coefficient associated with receptor activation. This inhibition is counteracted by millimolar concentrations of theophylline and MgCl2. Two nonhydrolyzable analogues of ATP, alpha, beta-Methyleneadenosine 5'-triphosphate and beta, gamma-methyleneadenosine 5'-triphosphate, also inhibit the increase in the partition coefficient. alpha, beta-Methyleneadenosine 5'-triphosphate is much more potent than ATP in doing so, and this compound was also shown to reduce the amount of receptor to bind to DNA-Sepharose after the incubations. Thus, adenine nucleotides induce a change in the state of the receptor, apparently consisting in an inhibition of receptor activation.     

Isolation,characterisation and expression of a cDNA for pea cholinephosphate cytidylyltransferase

In plants, phosphatidylcholine is the major phospholipid in extra-plastid membranes and is synthesised mainly by the CDP-choline pathway. Evidence from studies in animals, as well as in plants, suggests that the intermediate step catalysed by cholinephosphate cytidylyltransferase (CPCT) has a major control in carbon flux to this lipid. We have isolated a full-length CPCT cDNA (designated PCT2) from Pisum sativum cv. Feltham First using an Arabidopsis probe and the polymerase chain reaction (PCR). The deduced amino acid of PCT2 is 48%, 43% and 76% identical to the rat, yeast and Brassica napus amino acid sequences, respectively. Expression of the CPCT protein in Escherichia coli confirmed the activity of the enzyme. Expression of the PCT2 mRNA in pea roots and stems was increased by treatment with 0.1 µM indole-3-acetic acid.     

Chondroitin sulphate at the endothelial lumen of pig aorta: Assay by radiolabelling and by X-ray microanalysis

Trypsin-releasable glycosaminoglycans from the luminal surface of intact pig aorta were measured following metabolic labelling with³⁵S]sulphate. Chondroitin sulphate was found to be present at a surface density equal to that already established for heparan sulphate (5×10¹¹ chains per cm²). This result was confirmed by X-ray microanalysis of the luminal sulphur content before and after treatment with specific glycosaminoglycan-degrading enzymes. This result implies that approximately half of the luminal surface is occupied by sulphated glycosaminoglycans.