Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:1.1.1.27 (lactate dehydrogenase)
29,211 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Metabolism of lactate as a carbon source by Pseudomonas citronellolis occurred via a nicotinamide adenine dinucleotide (NAD)-independent L-lactate dehydrogenase, which was present in cells grown on DL-lactate but was not present in cells grown on acetate, aspartate, citrate, glucose, glutamate, or malate. The cells also possessed a constitutive, NAD-independent malate dehydrogenase instead of the conventional NAD-dependent malate dehydrogenase instead of the conventional NAD-dependent enzyme in the tricarboxylic acid cycle. Both enzymes were particulate and used dichlorophenolindo-phenol or oxygen as an electron acceptor. In acetate-grown cells, the activity of pyruvate dehydrogenase and NAD phosphate-linked malate enzyme decreased, cells grown on glucose or lactate. This was consistent with the need to maintain a supply of oxalacetate for metabolism of acetate via the tricarboxylic acid cycle. Changes in enzyme activities suggest that gluconeogenesis from noncarbohydrate carbon sources occurs via the malate enzyme (when oxalacetate decarboxylase is inhibited) or a combination of the NAD-independent malate dehydrogenase and oxalacetate decarboxylase.
...
PMID:Formation and dissimilation of oxalacetate and pyruvate Pseudomonas citronellolis grown on noncarbohydrate substrates. 1 74

The L-(+)-lactate dehydrogenase (L-lactate:NAD+ oxidoreductase, EC 1.1.1.27) of Streptococcus lactis C10, like that of other streptococci, was activated by fructose 1,6-diphosphate (FDP). The enzyme showed some activity in the absence of FDP, with a pH optimum of 8.2; FDP decreased the Km for both pyruvate and reduced nicotinamide adenine dinucleotide (NADH) and shifted the pH optimum to 6.9. Enzyme activity showed a hyperbolic response to both NADH and pyruvate in all the buffers tried except phosphate buffer, in which the response to increasing NADH was sigmoidal. The FDP concentration required for half-maximal velocity (FDP0.5V) was markedly influenced by the nature of the assay buffer used. Thus the FDP0.5V was 0.002 mM in 90 mM triethanolamine buffer, 0.2 mM in 90 mM tris(hydroxymethyl)aminomethanemaleate buffer, and 4.4 mM in 90 mM phosphate buffer. Phosphate inhibition of FDP binding is not a general property of streptococcal lactate dehydrogenase, since the FDP0.5V value for S. faecalis 8043 lactate dehydrogenase was not increased by phosphate. The S. faecalis and S. lactis lactate dehydrogenases also differed in that Mn2+ enhanced FDP binding in S. faecalis but had no effect on the S. lactis dehydrogenase. The FDP concentration (12 to 15 mM) found in S. lactis cells during logarithmic growth on a high-carbohydrate (3% lactose) medium would be adequate to give almost complete activation of the lactate dehydrogenase even if the high FDP0.5V value found in 90 mM phosphate were similar to the FDP requirement in vivo.
...
PMID:Fructose 1,6-diphosphate-activated L-lactate dehydrogenase from Streptococcus lactis: kinetic properties and factors affecting activation. 1 95

A method is described for the localization and characterization of phospholipases A1 and A2 (EC3.1.1.4) in Krebs II ascites cells, particularly in the plasma membranes. Cells were lysed with a Dounce homogenizer in an isotonic sucrose medium. Plasma membranes sediment with mitochondria and lysosomes during subcellular fractionation and are finally isolated on a continuous sucrose gradient. The membranes are localized at two levels in the gradient, at densities of 1.06 and 1.15, in which 5'-nucleotidase (EC 3.1.3.5) activity exhibits a 9- and 21-fold purification, respectively. Total contamination by endoplasmic reticulum, lysosomes, and mitochondria is 17 percent for the low-density membrane fraction and 25 percent for the high-density fraction. The phospholipases A present in Krebs II cells are active at pH 4.0 and pH 7.5. At the 2 pH values, they have A1 and A2 specificities. The intracellular distribution of acidic forms is comparable to that of acid phosphatase (EC 3.1.3.1), while neutral forms are localized like lactate dehydrogenase (EC 1.1.1.27). A small proportion of neutral phospholipase A2 has the same repartition on the sucrose gradient as nicotinamide adenine dinucleotide diaphorase (EF 1.6.4.3), an endoplasmic reticulum marker, and as 5'-nucleotidase, a plasma membrane marker.
...
PMID:Phospholipases A1 and A2 in subcellular fractions and plasma membranes of Krebs II ascites cells. 2 44

1. The pH-dependencies of the binding of NADH and reduced nicotinamide--benzimidazole dinucleotide to pig heart cytoplasmic malate dehydrogenase and lactate dehydrogenase are reported. 2. Two ionizing groups were observed in the binding of both reduced coenzymes to lactate dehydrogenase. One group, with pKa in the range 6.3--6.7, is the active-site histidine residue and its deprotonation weakens binding of reduced coenzyme 3-fold. Binding of both coenzymes is decreased to zero when a second group, of pKa 8.9, deprotonates. This group is not cysteine-165.3. Only one ionization is required to characterize the binding of the two reduced coenzymes to malate dehydrogenase. The group involved appears to be the active-site histidine residue, since its ethoxycarbonylation inhibits the enzyme and abolishes binding of reduced coenzyme. Binding of either reduced coenzyme increases the pKa of the group from 6.4 to 7.4, and deprotonation of the group is accompanied by a 10-fold weakening of coenzyme binding. 4. Two reactive histidine residues were detected per malate dehydrogenase dimer. 5. A mechanism which emphasizes the homology between the two enzymes is presented.
...
PMID:Malate dehydrogenase of the cytosol. Ionizations of the enzyme-reduced-coenzyme complex and a comparison with lactate dehydrogenase. 2 4

A rapid, sensitive and reliable method to measure lactate in blood is described. The method is based on the enzymatic oxidation of lactate to pyruvate in the presence of nicotinamide adenine dinucleotide (NAD+) and lactate dehydrogenase (LDH). The reaction product, NADH, is then oxidized by molecular oxygen, carried in the buffered reagent medium, in the presence of horeseradish peroxidase and other cofactors. The maximum rate of oxygen depletion, which is directly proportional to the amount of lactate ion present in the sample, is amperometrically monitored by a membrane oxygen electrode. No sample pretreatment is required in the present procedure other than dilution, and a comparison study between the described method and a spectrophotometric method shows good correlation.
...
PMID:A coupled enzymatic method to measure blood lactate by amperometric monitoring of the rate of oxygen depletion with a Clark oxygen electrode. 3 77

The reaction of pig heart lactate dehydrogenase with methyl methanethiosulphonate resulted in the modification of one thiol group per protomer, and this was located at cysteine-165 in the enzyme sequence. On reduction, both the thiomethylation of cysteine-165 and any changes in kinetic properties of the enzyme were completely reversed. Cysteine-165 has been considered essential for catalytic activity; however, cysteine-165-thiomethylated dehydrogenase possessed full catalytic activity, although the affinity of the enzyme for carbonyl-or hydroxy-containing substrates was markedly decreased. The nicotinamide nucleotide-binding capacity was unaffected, as judged by the formation of fluorescent complexes with NADH. The enzyme-mediated activation of NAD+, as judged by sulphite addition, was unaffected in thiomethylated lactate dehydrogenase. However, the affinity of oxamate for the enzyme--NADH complex was decreased by 100-fold and it was calculated that this constituted a net increase of 10.4 kJ/mol in the activation energy for binding. Thiomethylated lactate dehydrogenase was able to form an abortive adduct between NAD+ and fluoropyruvate. However, the equilibrium constant for adduct formation between pyruvate and NAD+ was too low to demonstrate this complex at reasonable pyruvate concentrations. A conformational change in the protein structure on selective thiomethylation was revealed by the decreased thermostability of the modified enzyme. The alteration of lactate dehydrogenase catalytic properties on modification depended on the bulk of the reagent used, since thioethylation resulted in an increase in Km for pyruvate (13.5 +/- 3.5 mm) and an 85% decrease in maximum catalytic activity. The implications of all these findings for the catalytic mechanism of lactate dehydrogenase are discussed.
...
PMID:A detailed investigation of the properties of lactate dehydrogenase in which the 'Essential' cysteine-165 is modified by thioalkylation. 3 72

The analogues of the coenzyme NADP+, nicotinamide--8-bromo-adenine dinucleotide phosphate (Nbr8ADP+) and 3-iodopyridine--adenine dinucleotide phosphate (io3PdADP+), were prepared. Nbr8ADP+ was found to be active in the hydrogen transfer adn io3PdADP+ is a coenzyme competitive inhibitor for 6-phosphogluconate dehydrogenase. The binding of NADP+, NADPH and NADPH together with 6-phosphogluconate as well as that of both analogues to crystals of the enzyme 6-phosphogluconate dehydrogenase has been investigated at 0.6-nm resolution using difference electron density maps. The molecules bind in a similar position in a cleft in the enzyme subunit distant from the dimer interface. The orientation of the coenzyme in the site has been determined from the io3PdADP+ -NADP+ difference density. The ternary complex difference density extends beyond that of the nicotinamide moiety of the coenzyme and tentatively indicates substrate binding. No clear identification of the bromine atom of Nbr8ADP+ can be made. However, the analogue is bound more deeply in the cleft than is NADP+. The NADPH density is the most clearly defined and has thus been used to fit a molecular model using an interactive graphics system, checking for preferred geometry. A possible conformation is presented which is significantly different from that of NAD+ in the lactate dehydrogenase ternary complex.
...
PMID:Binding of coenzyme and substrate and coenzyme analogues to 6-phosphogluconate dehydrogenase from sheep liver. An X-ray study at 0.6 nm resolution. 3 16

In the gastrocnemius muscle of cat and rat, staining for oxidative enzymes differentiated three fiber types (A,B,C) and staining for adenosine triphosphate at pH 9.4 differentiated two fiber types (I, II) with a reliability of 90% and 98%, respectively. In cat 96% and in rat 90% of the fibers were typed identically after staining for nicotinamide adenine dinucleotidelinked lactic dehydrogenase (LDH) and succinic dehydrogenase (SDH). When differentiated by staining for LDH, A and B fibers were of type I. IN RAT, 80-90% OF ALL FIBERS WERE OF TYPE 22, COMPPRISING A, B and C fibers. Type I fibers stained for LDH intensely as did C fibers of type II, but stained intermediately for SDH. The degree of staining was measured by photometry. When fibers were stained for LDH, histograms of density showed three peaks corresponding to A, B and C fibers in cat, but only two peaks corresponding to A and C fibers in rat, In cat and rat, the densities of A, B and C fibers belonged to different populations. In soleus muscle of cat and rat stained for LDH, menadione-linked alpha-glycerophosphate dehydrogenase and adenosine triphosphatase at pH 9.4, the degree of staining differed from thatin any type of fiber in gastrocnemius muscle
...
PMID:Histochemical fiber typing and staining intensity in cat and rat muscles. 12 97

Comparisons have been made between the active center geometries of lactate dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase, chymotrypsin and papain, and glyceraldehyde-3-phosphate dehydrogenase and papain. In the dehydrogenases, orientation of the nicotinamide ring about the glycosidic bond is determined by the substrate stereochemistry. The proper positioning of the carboxyamide moiety allows for the close approach of the C4 atom on the nicotinamide and the reactive carbon of the substrate. It follows that, once the conformation of the substrate or substrate intermediate has been established with respect to the functional groups in the enzyme, the A- or B-side specificity of the nicotinamide ring is predetermined. Hence, dehydrogenases which are divergently evolving from a common precursor must maintain the nicotinamide specificity if the protein fold of the catalytic domain is conserved. The tetrahedral intermediates produced during acylation of chymotrypsin and papain are found to be of opposite hand, while those of papain and glyceraldehyde-3-phosphate dehydrogenase can be regarded to be of the same hand. Thus the serine proteases, subtilisin and those of the chymotrypsin family, are of one hand while the cysteine enzymes, glyceraldehyde-3-phosphate dehydrogenase and papain, are of the other.
...
PMID:Convergence of active center geometries. 14 59

Formation of the binary complex between the reduced coenzyme nicotinamide adenine dinucleotide (NADH) and pig skeletal muscle lactate dehydrogenase (LDH, EC 1.1.1.27) has been investigated by calorimetric and equilibrium dialysis techniques in 0.2 M potassium phosphate buffer (pH 7.0) at various temperatures. Analysis of thermal titration curves at two temperatures (25 and 31.5 degrees) shows that the experimental enthalpy data can be rationalized assuming four independent and equivalent binding sites for the tetrameric enzyme. Binary complex formation is characterized by a negative temperature coefficient, delta cp, of the binding enthalpy, which amounts to -1300 plus or minus 53 cal/(deg mol of LDH) in the temperature range of 5-31.5 degrees. Despite the slightly smaller standard deviation resulting when polynomial regression analysis of the second degree is applied to the temperature dependence of the enthalpy values, binding enthalpies seem to be adequately represented in the temperature range studied by the equation delta H = -1.3T + 2.3, kcal/mol of LDH, T referring to the temperature in degrees C. By combination of the results obtained from equilibrium dialysis and calorimetric studies a set of apparent thermodynamic parameters for binding of NADH to LDH in 0.2 M potassium phosphate buffer at pH 7 has been established.
...
PMID:Thermodynamics of complex formation between nicotinamide adenine dinucleotide and pig skeletal muscle lactate dehydrogenase. 16 32


1 2 3 4 5 6 7 8 9 10 Next >>

---