Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.26.9 (ribonuclease)
 6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Native disulphide-bonded prolactin (band III) was distinguished from reduced prolactin (band II) and intermediate unstable disulphide-linked conformations by: (a) faster mobility of the former in sodium dodecyl sulphate/polyacrylamide gel electrophoresis, and (b) high-pressure liquid chromatography analyses of tryptic-digested peptides derived from prolactin in various conformations during its refolding pathway from reduced, unfolded to native conformation. The electrophoretic separation has been used to examine the state of disulphide bonding in newly synthesised prolactin translated from bovine pituitary mRNA in a rabbit reticulocyte translation system supplemented with nuclease-treated dog pancreatic microsomal membranes. The formation of correct disulphide pairing in prolactin (band III), synthesised in the in vitro translation system in the presence of pancreatic microsomes, required the presence of a thiol oxidant such as oxidised glutathione during the translation. The action of thiol oxidants on the in vitro biosynthesised and microsomally processed prolactin were both dose-dependent and catalytic; non-thiol oxidants such as NAD+ and NADP+ were ineffective. Examination of the time course of addition of oxidised glutathione to translating lysates showed that efficient and correct disulphide pairing in newly biosynthesised prolactin occurred when the oxidant was present co-translationally, but much lower yields of correctly disulphide-bonded prolactin were obtained when the oxidant was added after translation and processing were complete. The presence of protein-disulphide isomerase in dog pancreatic microsomes, employed in the in vitro translation system to process preprolactin, was demonstrated by (a) two-dimensional polyacrylamide gel electrophoresis of the membrane proteins, and (b) enzymic activity to accelerate reactivation of scrambled ribonuclease. Protein-disulphide isomerase activity was latent in intact microsomal vesicles, full activity being expressed upon sonication. A procedure has been devised to prepare pancreatic microsomal vesicles depleted of protein-disulphide isomerase which are active in processing and segregating in vitro biosynthesised prolactin. These membranes in the presence of low concentrations of oxidised glutathione are less active but in the presence of saturating levels of oxidised glutathione are fully competent in forming correct disulphide bridges in newly synthesised prolactin.
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PMID:Studies on the formation of intrachain disulphide bonds in newly biosynthesised bovine prolactin. Role of protein-disulphide isomerase. 406 47

The substrate specificity of diadenosine 5',5"'-P1,P4-tetraphosphate pyrophosphohydrolase from Physarum polycephalum for dinucleoside polyphosphates has been determined by high-performance liquid chromatography (HP-LC). Elution of a strong anion-exchange resin with a pH and ionic strength gradient of ammonium phosphate separates a series of monoadenosine and diadenosine polyphosphates. Most of the corresponding guanine nucleotides are also resolved on this HPLC system. One mole each of Ap4A and Gp4G is symmetrically hydrolyzed to 2 mol of ADP and GDP, respectively. Ap3A, Ap5A, Ap6A, and Ap4 are hydrolyzed, and in each case ADP is one of the products. Gp3G, Gp5G, Gp6G, and Gp4 are also substrates, and in each case GDP is one of the products. AMP, ADP, ATP, Ap2A, ADPR, GMP, GDP, GTP, NAD+, and NADP+ are not substrates. No hydrolysis of the cap dinucleotides m7Gp3Am and m7Gp3Cm was detected by HPLC. Diadenosine tetraphosphate pyrophosphohydrolase preparations were also assayed for adenylate kinase, nucleotide diphosphate kinase, NAD(P)+ pyrophosphohydrolase, phosphodiesterase, cyclic nucleotide phosphodiesterase, phosphatase, and ribonuclease activities. These enzymic activities were not detectable in diadenosine tetraphosphate pyrophosphohydrolase. The symmetrical hydrolysis of Ap4A and Gp4G is an unique catalytic property that distinguishes diadenosine tetraphosphate pyrophosphohydrolase from P. polycephalum from diadenosine tetraphosphate phosphohydrolases from other organisms.
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PMID:Diadenosine 5',5"'-P1,P4-tetraphosphate pyrophosphohydrolase from Physarum polycephalum. Substrate specificity. 629 57