Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.1.25 (triphosphatase)
 1,529 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mycelia of a low- and a high-production strain of Streptomyces aureofaciens were converted into protoplasts and divided into five subcellular fractions in order to localize exopolyphosphatases (EC 3.6.1.11), triphosphatase (EC 3.6.1.25), inorganic diphosphatase (EC 3.6.1.1), apyrase (EC 3.6.1.5) and glucokinase (EC 2.7.1.2). The highest specific activity of enzymes hydrolyzing polyphosphates was found in cytoplasmic vesicles and membranes. Triphosphatase was detected in the periplasmic fraction. Periplasmic vesicles and cytoplasm exhibited a high activity of diphosphatase. Apyrase was found mainly in the fractions of membranes and cytoplasmic vesicles. Glucokinase was a cytoplasmic enzyme. The enzymes were released from membrane structures into cytoplasm or periplasmic space if benzyl thiocyanate (10 microM) was present in the growth medium.
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PMID:Subcellular localization of enzymes in Streptomyces aureofaciens and its alteration by benzyl thiocyanate. I. Phosphatases and ATP-glucokinase. 282 19

Intact synaptosomes isolated from the electric organ of the electric ray Torpedo marmorata contain, at their surface, enzyme activities for the hydrolysis of externally applied nucleoside phosphates. The diazonium salt of sulfanilic acid, as a low-molecular-weight, slowly permeating, covalent inhibitory agent, selectively blocks these enzyme activities and leaves intracellular lactate dehydrogenase intact. The ectoenzymes comprise both a nucleoside triphosphate and diphosphate phosphohydrolase, as well as a 5'-nucleotidase. Activity of nonspecific ectophosphatases is absent. The nucleoside triphosphatase hydrolyzes almost equally well ATP, GTP, CTP, UTP, and ITP and is activated to a similar degree by Mg2+ or Ca2+. It has a high affinity for ATP (Km for ATP in the presence of Mg2+, 75 microM; in the presence of Ca2+, 66 microM). Maximal rates in the presence of Mg2+ and Ca2+ were very similar (34.8 and 32.5 nmol of Pi/min/mg of synaptosomal protein, respectively). Either Mg-ATP or Ca-ATP can act as a true substrate. ADP inhibits hydrolysis of ATP, but AMP is without effect. The nucleoside triphosphatase is not inhibited significantly by a number of inhibitors of mitochondrial Mg2+-ATPase or of Ca2+ + Mg2+-ATPases. It is, however, considerably inhibited by filipin and quercitin. The capacity of intact synaptosomes to hydrolyze also extracellular ADP, GDP, AMP, GMP, and IMP suggests that the nucleoside triphosphatase is part of an enzyme chain that causes complete hydrolysis of the respective nucleoside triphosphate to the nucleoside. We conclude that the cholinergic nerve terminals of the Torpedo electric organ can hydrolyze ATP released on coexocytosis with acetylcholine via an ectonucleoside triphosphatase activity that is different from known endogenous nerve terminal ATPases. The final product of the hydrolysis, adenosine, can then be salvaged by the nerve terminal for resynthesis of ATP. Other possible physiological functions of the ectonucleotidases are discussed.
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PMID:Ectonucleotidase activities associated with cholinergic synaptosomes isolated from Torpedo electric organ. 301 88

We have examined the RNA-capping enzyme activities of bluetongue virus (BTV) minor core protein, VP4. Recombinant BTV VP4 protein was purified to homogeneity from insect cell culture infected with a baculovirus VP4 of BTV serotype 10. We demonstrate that the purified protein, and VP4 encapsidated in core-like particles, react with GTP and covalently bind GMP via a phosphoamide linkage, a characteristic feature of guanylyltransferase enzyme. VP4 also catalyses a GTP-PPi exchange reaction indicating that the protein is the guanylyltransferase of the virus. In addition, VP4 possesses an RNA 5'-triphosphatase activity which catalyses the first step in the RNA-capping sequence. Further, an inorganic pyrophosphatase activity was identified which may aid the transcription activity within the virus by removing inorganic pyrophosphate which is an inhibitor of the polymerization reaction. Finally, the direct evidence of VP4 capping activity has been obtained by demonstrating in vitro transfer of GMP to the 5' end of in vitro synthesized BTV ssRNA transcripts to form a cap structure.
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PMID:Guanylyltransferase and RNA 5'-triphosphatase activities of the purified expressed VP4 protein of bluetongue virus. 967 55

Rat liver microsomes catalyze the hydrolysis of the triphosphates of adenosine, guanosine, uridine, cytidine, and inosine into the corresponding diphosphates and inorganic orthophosphate. The activities are stimulated by Na(2)S(2)O(4), and inhibited by atebrin, chlorpromazine, sodium azide, and deaminothyroxine. Sodium deoxycholate inhibits the ATPase activity in a progressive manner; the release of orthophosphate from GTP and UTP is stimulated by low, and inhibited by high, concentrations of deoxycholate, and that from CTP and ITP is unaffected by low, and inhibited by high, concentrations of deoxycholate. Subfractionation of microsomes with deoxycholate into ribosomal, membrane, and soluble fractions reveals a concentration of the triphosphatase activity in the membrane fraction. Rat liver microsomes also catalyze the hydrolysis of the diphosphates of the above nucleosides into the corresponding monophosphates and inorganic orthophosphate. Deoxycholate strongly enhances the GDPase, UDPase, and IDPase activities while causing no activation or even inhibition of the ADPase and CDPase activities. The diphosphatase is unaffected by Na(2)S(2)O(4) and is inhibited by azide and deaminothyroxine but not by atebrin or chlorpromazine. Upon fractionation of the microsomes with deoxycholate, a large part of the GDPase, UDPase, and IDPase activities is recovered in the soluble fraction. Mechanical disruption of the microsomes with an Ultra Turrax Blender both activates and releases the GDPase, UDPase, and IDPase activities, and the former effect occurs more readily than the latter. The GDPase, UDPase, and IDPase activities of the rat liver cell reside almost exclusively in the microsomal fraction, as revealed by comparative assays of the mitochondrial, microsomal, and final supernatant fractions of the homogenate. The microsomes exhibit relatively low nucleoside monophosphatase and inorganic pyrophosphatase activities, and these are unaffected by deoxycholate or mechanical treatment. Different approaches toward the function of the liver microsomal nucleoside tri- and diphosphatases are reported, and the possible physiological role of the two enzymes is discussed.
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PMID:A STUDY OF THE NUCLEOSIDE TRI- AND DIPHOSPHATE ACTIVITIES OF RAT LIVER MICROSOMES. 1986 15