Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.21.1 (DNase)
 7,655 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Modification of the histidine residues of purified S1 nuclease resulted in loss of its single-stranded (ss)DNAase, RNAase and phosphomonoesterase activities. Kinetics of inactivation indicated the involvement of a single histidine residue in the catalytic activity of the enzyme. Furthermore, histidine modification was accompanied by the concomitant loss of all the activities of the enzyme, indicating the presence of a common catalytic site responsible for the hydrolysis of ssDNA, RNA and 3'-AMP. Substrate protection was not observed against Methylene Blue- and diethyl pyrocarbonate (DEP)-mediated inactivation. The histidine (DEP)-modified enzyme could effectively bind 5'-AMP, a competitive inhibitor of S1 nuclease, whereas the lysine (2,4,6-trinitrobenzenesulphonic acid)-modified enzyme showed a significant decrease in its ability to bind 5'-AMP. The inability of the substrates to protect the enzyme against DEP-mediated inactivation, coupled with the ability of the modified enzyme to bind 5'-AMP effectively, suggests the involvement of histidine in catalysis.
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PMID:Active-site characterization of S1 nuclease. II. Involvement of histidine in catalysis. 146 60

A simple procedure, involving heat-treatment, DEAE-Sephadex, AMP-Sepharose and Bio-Gel P-60 chromatography, was developed for the purification of S1 nuclease to homogeneity from commercially available Takadiastase powder. Chemical modification of the amino groups of purified S1 nuclease revealed that lysine is essential for single-stranded DNAase, RNAase and phosphomonoesterase activities associated with the enzyme. The kinetics of inactivation suggested the involvement of a single lysine residue in the active site of the enzyme. Additionally, lysine modification was accompanied by a concomitant loss of all the activities of the enzyme, indicating the presence of a common catalytic site responsible for the hydrolysis of single-stranded DNA, RNA and 3'-AMP. Substrate-protection and inhibitor-binding studies on enzyme modified with 2,4,6-trinitrobenzenesulphonic acid showed that lysine may be involved in the substrate binding.
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PMID:Active-site characterization of S1 nuclease. I. Affinity purification and influence of amino-group modification. 163 40

Incubation of barley (Hordeum vulgare L. cv Himalaya) half-seeds with gibberellic acid enhances the secretion of ribonuclease and deoxyribonuclease from aleurone tissue (MJ Chrispeels, JE Varner 1967 Plant Physiol 42: 398-406; L Taiz, JE Starks 1977 Plant Physiol 60: 182-189). These activities were over 50-fold greater in medium of half-seeds incubated with gibberellic acid than in control medium. Ribonuclease and deoxyribonuclease activities initially appeared in the medium 24 to 48 hours after hormone induction and increased for up to 96 hours. Both activities had a pH optimum of 6.0 and a temperature optimum of 55 degrees C. When the medium from gibberellic acid-treated half-seeds was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis, the major ribonuclease and deoxyribonuclease activity bands comigrated. The two enzyme activities remained associated throughout a 2,700-fold purification employing ammonium sulfate fractionation, Heparin-Agarose affinity chromatography, and Reactive Blue 2-Agarose affinity chromatography. Also accompanying the ribonuclease and deoxyribonuclease activities throughout purification was the ability to hydrolyze the 3'-phosphoester linkage of 3'-AMP. The purified protein was composed of a single polypeptide with an apparent molecular weight of 36 kilodaltons as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. It is concluded that in response to gibberellic acid, barley aleurone tissue secretes a nuclease having ribonuclease, deoxyribonuclease, and 3'-nucleotidase activities.
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PMID:Barley aleurone layers secrete a nuclease in response to gibberellic Acid : purification and partial characterization of the associated ribonuclease, deoxyribonuclease, and 3'-nucleotidase activities. 1666 13