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)

The synthesis of cytidine, uridine, guanosine, and adenosine 3'-(S-methyl phosphorothioates) by treatment of the 2',5'-di-O-(4-methoxytetrahydropyran-4-yl)ribonucleosides with 2-(methylthio 4H-1,3,2-benzodioxaphosphorin 2-oxide is described. These nucleotide analogues are stable compounds both in the solid state and the neutral aqueous solution. All four of these compounds are degraded by RNase T2 to the parent nucleotides and methanethiol. In addition, cytidine and uridine 3'-(S-methyl phosphorothioates) are substrates for bovine pancreatic ribonuclease and guanosine 3'-(S-methyl phosphorothioate) is a substrate for RNase T1 and RNase U1. When used in conjunction with a chromophore-producing reagent, nucleoside 3'-(S-methyl phosphorothioates) provide a means for direct kinetic measurement of ribonuclease activity over a wide pH range (pH 2-9). The reactivities of these substrates with ribonucleases are compared to the reactivities of other synthetic substrates as well as a number of natural substrates. The utility of ribonucleoside 3'-(S-methyl phosphorothioates) as substrates for the assay of ribonucleases is discussed.
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PMID:Synthesis of nucleoside 3'-(S-alkyl phosphorothioates) and their use as substrates for nucleases. 627 Nov 88

The reaction of L-3a-hydroxy-1,2,3a,8,8a-hexahydropyrrolo[2,3-b]indole-2-carboxylic acid (Hpi) with methanethiol, ethanethiol, mercaptoethanol or 3-mercaptopropionic acid in warm aqueous acetic acid gives the corresponding 2-thioether derivatives of tryptophan in 50--80% yield (based on Hpi). Better yields may be obtained in 25% trifluoroacetic acid at room temperature. Cysteine reacts with Hpi to give the double amino acid 2-(L-3-alanylthio)-L-tryptophan (tryptathionine), which is a constituent of the highly poisonous cyclopeptides of Amanita phalloides, such as phalloidin. Reaction of a moderate excess of Hpi with cysteine-SH groups of a tripeptide (glutathione) and a protein (reduced ribonuclease) has also been effected, giving the respective S-tryptophanylated peptide or protein. In both cases, reaction occurred specifically with the -SH groups of cysteine and virtually quantitative covalent binding of tryptophan was verified. The extent of the reaction is easily quantitated by spectrophotometry or by amino acid analysis of the content of oxindolylalanine in the hydrolysate with hot 3-N p-toluenesulfonic acid of the S-tryptophanylated peptide or protein. The reaction should be useful in the field of peptide synthesis, providing a simple method for establishing a cross-link between tryptophan and cysteine, as a basic step in the chemical synthesis of toxic peptides of Amanita phalloides.
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PMID:A novel synthesis of 2-thioether derivatives of tryptophan. Covalent binding of tryptophan to cysteine sulfhydryl groups in peptides and proteins. 737 2