Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Specific activity of 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) was measured in 48 tissue specimens of human female breast cancer and, in addition, 48 nonmalignant tissue specimens obtained in each case from the same cancer-bearing breast. In all cases the nonmalignant tissue showed greater conversion of estradiol-17 beta into estrone than the neoplastic tissues. In normal human breast tissue of premenopausal women specific enzyme activity depended on the phase of the MENSTRUAL CYCLE: the highest values of 17 beta-HSD activity were found in the early secretory phase. To determine the intracellular distribution of the 17 beta-HSD, purified microsomes, mitochondria, peroxysomes, lysosomes, nuclei and cytosol fractions were prepared. The purity of each fraction was monitored by marker enzymes. It was found that the 17 beta-HSD was mainly located in mitochondria and microsomes. Furthermore it could be demonstrated that the microsomal enzyme was bound tightly to the membranes of the endoplasmic reticulum, while the mitochondrial 17 beta-HSD was mainly associated with the outer membranes of the organelle. Kinetic parameters (Km-values, coenzyme requirements and maximal velocities) of a cytoplasmic, nuclear, mitochondrial and microsomal 17 beta-HSD of normal and neoplastic human mammary tissue were compared. Maximal velocity was highest in enzyme preparations of normal mammary tissue obtained from premenopausal women in the early secretory phase. Km-values wrere nearly identical in normal and neoplastic mammary tissue preparations (approx. 1 X 10(-6) M). NAD was more efficient than NADP as a cofactor. For the conversion of estradiol to estrone the optimum temperature was approximately 40 degrees C and the optimum pH 9.5. For the reduction of estrone the optimum pH was 6.5. Sulphydryl groups were shown to be essential for catalysis.
Mol Cell Endocrinol 1977 Feb
PMID:Comparison of the in vitro conversion of estradiol-17 beta to estrone of normal and neoplastic human breast tissue. 1 41

3-Aminopyridine mononucleotide, a nicotinamide mononucleotide analog, was prepared by enzymatic cleavage of 3-aminopyridine adenine dinucleotide by a snake venom phosphodiesterase and isolated by means of ion exchange chromatography. The spectrophotometric and fluorometric properties of this analog were studied. Several anions were shown to quench the fluorescence intensity of this analog. pH was shown to have a pronounced effect on the fluorescence intensity. 3-Aminopyridine mononucleotide was shown to be a coenzyme-competitive inhibitor of yeast alcohol dehydrogenase. The 3-aminopyridine mononucleotide was diazotized with the use of nitrous acid. A time dependent irreversible inactivation of yeast alcohol dehydrogenase resulted from incubation with the diazotized 3-aminopyridine mononucleotide at pH 7.0. Incubation of the enzyme with NAD prior to the addition of the diazotized 3-aminopyridine mononucleotid protected the enzyme against inactivation.
Mol Cell Biochem 1977 Mar 21
PMID:Studies of yeast alcohol dehydrogenase with 3-aminopyridine monucleotide. 1 65

We have studied the isocitrate dehydrogenase of Tetrahymena pyriformis. This enzyme is able to utilize both NAD and NADP, but kinetic studies suggest that the enzymatic activity with NAD is not of physiological signifance. Some of the factors that might regualte the NADP-dependent isocitrate dehydrogenase were also studied. This enzyme has an absolute requirement for divalent cations; Mg,+ and Mn2+ will serve as cofactors but the latter is more effective than the former. It is known that this enzyme is subject to a concerted inhibition by oxaloacetate and glyoxylate. Either glyoxylate or oxaloacetate alone also are capable of inhibiting the enzyme although higher concentrations are required. We have found concerted inhibition also for the NAD-dependent isocitrate dehydrogenase from rat liver and yeast. The activity of the Tetrahymena pyriformis enzyme is inhibited by NADPH. This inhibition is competitive with NADP. The Ki and Km values are, respectively, 20 micrometers and 18 micrometers.
Mol Cell Biochem 1977 Oct 07
PMID:Isocitrate dehydrogenase of Tetrahymena pyriformis. 2 34

NAD(P)H: FMN oxidoreductase (flavin reductase) couples in vitro to bacterial luciferase. This reductase, which is also postulated to supply reduced flavin mononucleotide in vivo as a substrate for the bioluminescent reaction, has been partially purified and characterized from two species of luminous bacterial. From Photobacterium fischeri the enzyme has a M. W. determined by Sephadex gel filtration, of 43,000 and may have a subunit structure. The turnover number at 20 degrees C, based on a purity estimate of 20 percent, is 1.7 times 10-4 moles of NADH oxidized per min per mole of reductase. The reductase isolated from Beneckea harveyi has an apparent molecular weight of 23,000; its purity was too low to permit estimation of specific activity. Using a spectrophotometric assay at 340 nm with the P. fischeri reductase, both NADH (Km, 8 times 10-5 M) and NADPH (Km, 4 times 10-4 M) were enzymatically oxidized, the Vmax with NADH being approximately twice that of NADPH. Of the flavins tested in this assay, only FMN (Km, 7.3 times 10-5 M) and FAD (Km, 1.4 times 10-4 M) were effective, FMN having a Vmax three times that of FAD. In the coupled assay, i.e., measuring the bioluminescence intensity of the reaction with added luciferase, the optimum FMN concentration was nearly 100 times less than in the spectrophotometric assay. The studies reported suggest the existence of a functional reductase-luciferase complex.
Mol Cell Biochem 1975 Jan 31
PMID:Flavin mononucleotide reductase of luminous bacteria. 4 4

The cell-free extract from blue-green alga Anacystis nidulans contains enzymatic activities which repair in vitro transforming DNA of bacteriophage T4 damaged by UV light or X-rays. The repair effect of the extract was observed with double-stranded irradiated DNA but not with denatured irradiated DNA. The level of restoration of the transforming activity depends on the protein concentration in the reaction mixture and on the dose of irradiation. A fraction of DNA lesions induced by X-rays is repaired by a NAD-dependent polynucleotide ligase present in the extract. The repair of UV-induced lesions is the most efficient in the presence of magnesium ions, NAD, ATP and the four deoxynucleoside triphosphates. The results indicate that the repair of UV-irradiated DNA is performed with the participation of DNA polymerase and polynucleotide ligase which function in the cell-free extract of the algae on the background of a low deoxyribonuclease activity.
Mol Biol Rep 1975 Jul
PMID:In vitro repair of UV-or x-irradiated bacteriophage T4 DNA by extract from blue-green alga Anacystis nidulans. 16 64

Flounder muscle (Pseudopleuronectes americanus) glyceraldehyde-3-phosphate dehydrogenase was characterized as to its stability towards various inactivating treatments in the presence and absence of the enzyme cofactor, NAD. Incubation of a partially purified enzyme preparation at urea concentrations greater than 2 M produced a very rapid inactivation. NAD greatly reduced the rate of inactivation at all the urea concentrations tested. Incubation of each of the three major muscle enzyme forms in 0.1 percent trypsin or chymotrypsin for forty-five minutes decreased the activity of each form by 65 percent and 55 percent, respectively. NAD (5mM) afforded complete protection to each enzyme form from proteolytic digestion by these two enzymes. Exposure of each form to 50 degrees or 20 mM ATP also led to gross inactivation which could be greatly reduced if the respective incubations were performed in the presence of 5mM NAD. NAD was also found to be required for the renaturation of the unfolded urea-denatured subunits to form the active tetramer.
Mol Cell Biochem 1975 Sep 30
PMID:Effect of NAD on flounder muscle glyceraldehyde 3-phosphate dehydrogenase. 17 55

A mutation leading to partial loss of NAD-linked ("catabolic') glutamate dehydrogenase does not affect the regulation of ammonium-repressible activities in Aspergillus nidulans. This mutation has been used to show that NAD-linked glutamate dehydrogenase does not normally participate in ammonium assimilation. A mutation leading to loss of NADP-linked ("anabolic') glutamate dehydrogenase has been used to show that NADP-linked glutamate dehydrogenase is not normally involved in glutamate catabolism. Strains defective in either enzyme are useful for determining which amino acids are metabolised via transamination to yield glutamate rather than via deamination to yield ammonium.
Mol Gen Genet 1975
PMID:A mutant of Aspergillus nidulans defective in NAD-linked glutamate dehydrogenase. 17 77

Using NAD analogues as ligands, the structural requirements for negative cooperativity in binding to rabbit muscle glyceraldehyde-3-phosphate dehydrogenase were examined. Although the affinity of nicotinamide hypoxanthine dinucleotide is considerably lower than that of NAD+, it also binds to the enzyme with negative cooperatively. Two pairs of nicotinamide hypoxanthine dinucleotide binding sitess were distinguished, one pair having an affinity for the analogue which is 15 times that of the second pair. Negative cooperativity is also found in the Km values for the analogue. Thus modification of the adenine ring of NAD+ to hypoxanthine does not abolish negative cooperativity in coenzyme binding. Adenosine diphosphoribose binding to the same enzyme shows neither positive nor negative cooperativity, indicating that cooperativity apparently requires an intact nicotinamide ring in the coenzyme structure, under the conditions of these experiments. Occupancy of the nicotinamide subsite of the coenzyme binding site is not necessary for half-of-sites reactivity of alkylating or acylating compounds (Levitzki, A. (1974), J. Mol, Biol. 90, 451-458). However, it can be important in the negative cooperativity in ligand binding, as illustrated by adenosine diphosphoribose which fails to exhibit negative cooperativity. Occupancy of the adenine subsite by adenine is important for stabilization of the enzyme against thermal denaturation. Whether the stabilization is due to an altered conformation of the subunits or stabilization of the preexisting structure of the apoenzyme cannot be determined from these studies. However, nicotinamide hypoxanthine dinucleotide does not contribute to enzyme stability although it serves as a substrate and shows negative cooperativity.
 ...
PMID:Cooperativity and noncooperativity in the binding of NAD analogues to rabbit muscle glyceraldehyde-3-phosphate dehydrogenase. 17 63

The kinetic method and selective chemical modification have been used in studies of the kinetic manifestations of active site interactions in D-glyceraldehyde-3-phosphate dehydrogenase (GAP dehydrogenase). The reactions of glyceraldehyde and glyceraldehyde-3-phosphate oxidation were studied in the absence of substrate excess. In support of the data obtained previously it was shown that only a part of the tightly bound NAD molecules can be reduced after substrate addition. "Partial reducibility" is observed at various degrees of saturation of the enzyme with NAD involving a single NAD molecule per tetrametric enzyme. These facts can hardly be explained by assumption of functional non-equivalence of active sites, whether induced by coenzyme or preexisting in the apoenzyme. It was proven by selective alkylation of the catalytic SH groups that "partial reducibility" is due to the circumstance that equilibrium in the system under investigation is established at nearly equal NAD and NADH concentrations. A plot of initial reaction rates versus NAD concentration (at non-saturating substrate concentrations) gives S-shaped curves; this is explained by considerable enzyme activation upon saturation of the fourth site with coenzyme. After modification of three active sites with iodoacetate the S-shape of the curve disappeared. This fact leads to the conclusion that active site interactions are required for formation of the S-shaped curves. The activity of a single site functioning in the modified enzyme reached values equal to those of the active sites in the native enzyme in the fully activated state. A model is proposed which can explaine the variations in mode of enzyme activation in the native and modified states. It is suggested that the surroundings of all four SH groups must be altered in order to activate the enzyme; such changes can be induced either by alkylation of the SH groups or by NAD binding. Evidence is presented that important functional properties of GAP dehydrogenase cannot be elucidated at low enzyme concentrations and with excess of substrates: three active sites are saturated under such conditons and practically inactive, and the fourth site obeys Michaelis - Menten kinetics.
Mol Biol (Mosk)
PMID:[Kinetic manifestations of the interaction of active centers in swine skeletal muscle D-glyceraldehyde-3-phosphate dehydrogenase]. 18 4

Progesterone causes in goblet cells of oviducts of estrogen hormone-stimulated immature quails selectively gene activation without affecting DNA synthesis. This biological model has been used to study the influence of poly ADP-ribosylation during the processes of DNA transcription. Administration of progesterone in vivo causes an increase of the activity of RNA polymerase I and II in isolated nuclei. This increase is accompanied by a marked decrease of the specific activity of poly (ADP-Rib) polymerase. After in vitro ADP-ribosylation of nuclear proteins the template capacity of chromatin for ""exogenous'' RNA synthesis (with E. coli DNA-dependent RNA polymerases) as well as for ""endogenous'' RNA synthesis with DNA dependent RNA polymerases II is not affected, whereas the data presented seem to indicate that the capacity for RNA synthesis mediated by ""endogenous'' DNA-dependent RNA polymerase I might be inhibited after ADP-ribosylation. Evidence is presented to show that a considerable amount of poly (ADP-Rib), synthesized by poly (ADP-Rib) polymerase in isolated nuclei, is linked with RNA polymerase I. The rate of synthesis of poly (ADP-Rib) is dependent on the incubation temperature (optimum at 25 degrees C) and it can be inhibited by the specific inhibitors of poly (ADP-Rib) polymerase nicotineamide, thymidine and formycin B. Poly (ADP-Rib) is probably associated with RNA polymerase I through a covalent linkage. ADP-ribosylated RNA polymerase I has been purified 550 fold with respect to the nuclear extract corresponding to a 4,000 fold purification from the whole cell homogenate. The ratio between poly (ADP-Rib), formed during preincubation of nuclei with NAD, and RNA polymerase I remains almost constant during the purification procedures. The extent of ADP-ribosylation of RNA polymerase I decreases during gene expression. Thus we conclude that poly ADP-ribosylation of this enzyme is one of the regulatory mechanisms by which specificity of DNA transcription is achieved.
Mol Cell Biochem 1976 Sep 30
PMID:Poly ADP-ribosylation of DNA-dependent RNA polymerase I from quail oviduct. Dependence on progesterone stimulation. 18 9


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