Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.4 (ribonuclease)
 6,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Fumarase (EC 4.2.1.2) and mitochondrial L-malate dehydrogenase (EC 1.1.1.37) were both inhibited by NaAuCl4 and KAuBr4. The inhibition for both was measured as a function of gold complex concentration and aquation time, and the NaAuCl4 inhibition was also measured in the presence of 0.15 M NaCl. Regeneration of the enzyme activity after NaAuCl4 inhibition using L-cysteine, L-methionine and NaCN was also investigated. Sodium dodecyl sulfate (SDS) acrylamide gel electrophoresis and amino acid analysis was performed on the NaAuCl4 inhibited enzymes as well as on ribonuclease A (EC 3.1.26.2), lysozyme (EC 3.2.1.17) and liver alcohol dehydrogenase (EC 1.1.1.1). It was observed that the inhibition was proportional to the gold complex concentration but decreased markedly after aquation of the complex. In the presence of NaCl the initial rate of inactivation is essentially unaffected unless the complex has been aquated and then the initial rate is increased. Gel electrophoresis on gold complex-enzyme mixtures show polymerization for ribonuclease and lysozyme and amino acid analysis indicates that no oxidation has taken place. From these results, a binding mechanism is postulated for the inhibition of the dehydrogenases by direct displacement of a halide ligand, probably by two groups on the enzyme, at least one of which may be a sulfur containing acid.
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PMID:Inhibition of two mitochondrial enzymes by gold (III) halo complexes. Evidence for a binding mechanism. 715 Dec 34

The Aspergillus ribonuclease alpha-sarcin is toxic to intact mammalian cells but the mechanism by which it enters the cells to reach its ribosomal RNA substrate is unclear. Here we have compared the cytotoxicity of alpha-sarcin to that of ricin, another catalytic toxin that targets the same rRNA sequence but whose mechanism of cell entry is better understood. Intact ricin binds to cell surface components and enters the cells by receptor-mediated endocytosis, whereas the catalytic polypeptide of ricin (the A chain or RTA) which, like alpha-sarcin, is unable to bind to surface components directly and enters cells by fluid phase uptake. Recombinant alpha-sarcin was produced in Escherichia coli and purified to homogeneity. The protein was soluble, stable and its ability to inhibit in vitro protein synthesis was indistinguishable from that of native alpha-sarcin. Further, recombinant alpha-sarcin had the same in vitro protein synthesis inhibition activity as ricin A chain. The cytotoxicity of alpha-sarcin and ricin A chain to HeLa cells was also the same. The cytotoxicity of alpha-sarcin was due to its RNAase activity rather than to specific membrane effects at the cell surface, since a mutant containing a single substitution at a putative key catalytic residue had reduced ribonuclease activity and an equivalent reduction in cytotoxicity. One interpretation of the data is that a-sarcin enters mammalian cells in the same way as free ricin A chain.
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PMID:Characterization of prokaryotic recombinant Aspergillus ribotoxin alpha-sarcin. 929 21