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PubMed2006

[A study of genetic diversity in lactate dehydrogenase of Streptococcus mutans from clinical isolates].

OBJECTIVES: Lactate dehydrogenase (LDH) is shown to be an important virulence factor resulting in acid production of Streptococcus mutans (S. mutans), on which the cariogenic potential of S. mutans depends. Differences in cariogenic abilities of S. mutans isolates may be determined by genetic heterogeneity from virulent factors. The relationship between LDH activity or genetic diversity and cariogenicity of S. mutans (serotype c) isolates was studied in this research. METHODS: The genome DNA of S. mutans isolates were isolated and LDH gene (ldh) were amplified with specific primers. These isolates came from 34 caries-active individuals and 36 caries-free ones, in which 24 strains showed the high LDH activity and 21 strains showed the low LDH activity. Then genetic diversity of PCR products were analyzed or assessed by restriction fragment-length polymorphism (RFLP). Some of amplified LDH genes from different group were sequenced and assayed. RESULTS: It is testified that two genotypes A and B of ldh-RFLP were revealed when LDH genes were digested with Mse I, but Hph I, Mnl I, Dde I, Nla III and Alu I digesting fragments of Idh gene did not show different pattern. Furthermore, Fisher Exact one-Tail Test showed that the proportion of genotype B among strains from caries-free individuals was higher than that from caries-active ones (P = 0.033), while the distribution of genotypes with different LDH activity was different between two groups (two-Tail Test P = 0.017). The sequencing DNA testified that the specific base mutation would lead to multiple kind of genotype resulted. CONCLUSION: This study indicated that LDH gene of S. mutans clinical strains from different individuals is conservative, while there still is the gene mutation in. The ldh genetic diversity may be related to the low caries sensitivity, and closely correlated with the differences in LDH enzyme activity of S. mutans strains.

DNA, Bacterial↗
PubMed2005

Cyclic AMP and AKAP-mediated targeting of protein kinase A regulates lactate dehydrogenase subunit A mRNA stability.

Expression of the lactate dehydrogenase A subunit (ldh-A) gene is controlled through transcriptional as well as post-transcriptional mechanisms. Both mechanisms involve activation of protein kinase A (PKA) into its subunits and subsequent phosphorylation and activation of several key regulatory factors. In rat C6 glioma cells, post-transcriptional gene regulation occurs through PKA-mediated stabilization of LDH-A mRNA and subsequent increase of intracellular LDH-A mRNA levels. Previous studies have demonstrated a cAMP-stabilizing region (CSR) located in the LDH-A 3'-untranslated region which, in combination with several phosphorylated CSR-binding proteins (CSR-BP), regulates the PKA-mediated stabilization of LDH-A mRNA. However, the mechanistic details of interaction of CSR with proteins as they pertain to mRNA stabilization by PKA are so far largely unknown. In this study we tested the hypothesis that ribosomal protein extracts (RSW) from glioma cells contain PKA regulatory (RII) and catalytic (C) subunits that, in combination with a protein kinase A anchoring protein (AKAP 95) and CSR-BPs participate in forming CSR-protein complexes that are responsible for mRNA stability regulation. To demonstrate the importance of CSR-protein complex formation, the PKA subunits and AKAP 95 were removed from the RSW by immunoprecipitation, and the antigen-deleted RSW were subjected to CSR binding analysis using gel mobility shift and UV cross-linking. It was shown that AKAP 95 as well as RII formed a direct linkage with CSR during CSR-protein complex formation. In contrast, the catalytic subunit formed part of the CSR-protein complex but did not bind to CSR directly in a covalent linkage. To determine whether formation of CSR complexes that included C, RII, and AKAP 95 constituted a functional event and was necessary for mRNA stabilization, cell-free decay reactions were carried out with RSW extracts, and the kinetics of decay of LDH-A mRNA was determined. Depletion of PKA subunits and AKAP 95 from RSW extracts by immunoprecipitation resulted in a marked loss of mRNA stabilization activity indicating that the presence of the PKA regulatory and catalytic subunits as well as AKAP 95 in the CSR-protein complexes was absolutely necessary to achieve LDH-A mRNA stabilization.

3' Untranslated Regions↗
PubMed2004

[Expression and characterization of subunit C of mouse lactate dehydrogenase in Escherichia coli].

OBJECTIVES: To construct a prokaryotic recombinant vector for mouse lactate dehydrogenase-C and to detect its expression in BL21. METHODS: The coding sequence of mouse lactate dehydrogenase subunit C was amplified from mouse testis RNA with specific primers, and cloned into pGEX-2T after the restriction digestion with BamH I and EcoR I. GST fusion protein was expressed after induction with IPTG. RESULTS: Sequencing and restriction digestion of the recombinant plasmid revealed the existence of coding sequence for mouse lactate dehydrogenase subunit C. A protein band of about 60,000 could be induced by IPTG in the recombinant plasmid. CONCLUSIONS: The coding sequence of mouse lactate dehydrogenase subunit C was introduced into the pGEX-2T plasmid and a GST-fused protein could be induced at a high level.

Animals↗
PubMed1979

Lactate dehydrogenase isoenzyme transitions during skeletal differentiation in the mouse embryo.

(1) In the mouse embryo there are changes in lactate dehydrogenase activity and isoenzyme pattern during the differentiation of cartilage and bone. (2) The specific activity of lactate dehydrogenase rises during chondrogenesis and falls during osteogenesis. (3) Identical isoenzyme transitions occur in parallel in both tissues: undifferentiated limb bud mesenchyme contains isoenzymes 1-5 whereas in both the cartilaginous and bony portions of a long bone developing from the mesenchyme, there is a progressive shift towards a predominance of the 'anaerobic' isoenzymes 4 and 5.

Aging↗
PubMed2002

Domain closure, substrate specificity and catalysis of D-lactate dehydrogenase from Lactobacillus bulgaricus.

NAD-dependent Lactobacillus bulgaricus D-Lactate dehydrogenase (D-LDHb) catalyses the reversible conversion of pyruvate into D-lactate. Crystals of D-LDHb complexed with NADH were grown and X-ray data collected to 2.2 A. The structure of D-LDHb was solved by molecular replacement using the dimeric Lactobacillus helveticus D-LDH as a model and was refined to an R-factor of 20.7%. The two subunits of the enzyme display strong asymmetry due to different crystal environments. The opening angles of the two catalytic domains with respect to the core coenzyme binding domains differ by 16 degrees. Subunit A is in an "open" conformation typical for a dehydrogenase apo enzyme and subunit B is "closed". The NADH-binding site in subunit A is only 30% occupied, while in subunit B it is fully occupied and there is a sulphate ion in the substrate-binding pocket. A pyruvate molecule has been modelled in the active site and its orientation is in agreement with existing kinetic and structural data. On domain closure, a cluster of hydrophobic residues packs tightly around the methyl group of the modelled pyruvate molecule. At least three residues from this cluster govern the substrate specificity. Substrate binding itself contributes to the stabilisation of domain closure and activation of the enzyme. In pyruvate reduction, D-LDH can adapt another protonated residue, a lysine residue, to accomplish the role of the acid catalyst His296. Required lowering of the lysine pK(a) value is explained on the basis of the H296K mutant structure.

Binding Sites↗
PubMed1990

Kinetic properties of two transaminases and lactate dehydrogenase of Biomphalaria alexandrina snails, intermediate hosts of Schistosoma mansoni.

Aspartate (AST) and alanine (ALT) aminotransferase together with lactate dehydrogenase (LD) from the tissue homogenate of the Biomphalaria alexandrina snails, were partially characterized by measuring the Michaelis constant (km) and the maximum velocity (Vmax). The isoenzymatic pattern of lactate dehydrogenase was investigated through polyacrylamide gel electrophoresis.

Alanine Transaminase↗
PubMed1998

Sorting of D-lactate dehydrogenase to the inner membrane of mitochondria. Analysis of topogenic signal and energetic requirements.

D-Lactate dehydrogenase (D-LD) is located in the inner membrane of mitochondria. It spans the membrane once in an Nin-Cout orientation with the bulk of the protein residing as a folded domain in the intermembrane space. D-LD is synthesized as a precursor with an N-terminal cleavable presequence and is imported into the mitochondria in a Deltapsi-dependent, but mt-Hsp70-independent manner. Upon import in vitro D-LD folds in the intermembrane space to attain a conformation indistinguishable from endogenous D-LD. Sorting of D-LD to the inner membrane is directed by a composite topogenic signal consisting of the hydrophobic transmembrane segment and a cluster of charged amino acids C-terminal to it. We propose a model for the mode of operation of the sorting signal of D-LD. This model also accounts for the driving force of translocation across the outer membrane, in the apparent absence of mt-Hsp70-dependent assisted import and involves the folding of the D-LD in the intermembrane space.

Cell Membrane↗
PubMed1993

Dissociation of lactate dehydrogenase in aqueous and reversed micellar solutions. A time-resolved polarized fluorescence study.

Dissociation behavior of lactate dehydrogenase from hog muscle, both in aqueous solution and reversed micelles of sodium bis(2-ethylhexyl sulfosuccinate) in octane was studied using time-resolved polarized fluorescence spectroscopy. It was found that, in aqueous solutions, the enzyme underwent partial dissociation with the formation of isolated subunits at enzyme concentrations below 8 nM. Dissociation of the enzyme also took place upon entrapment of lactate dehydrogenase into reversed micelles under conditions of low surfactant hydration, when micelles were not large enough to accommodate a whole protein molecule.

Animals↗
PubMed2004

Electron acquisition system constructed from an NAD-independent D-lactate dehydrogenase and cytochrome c2 in Rhodopseudomonas palustris No. 7.

The activities of NAD-independent D- and L-lactate dehydrogenases (D-LDH, L-LDH) were detected in Rhodopseudomonas palustris No. 7 grown photoanaerobically on lactate. One of these enzymes, D-LDH, was purified as an electrophoretically homogeneous protein (M(r), about 235,000; subunit M(r) about 57,000). The pI was 5.0. The optimum pH and temperature of the enzyme were pH 8.5 and 50 degrees C, respectively. The Km of the enzyme for D-lactate was 0.8 mM. The enzyme had narrow substrate specificity (D-lactate and DL-2-hydroxybutyrate). The enzymatic activity was competitively inhibited by oxalate (Ki, 0.12 mM). The enzyme contained a FAD cofactor. Cytochrome c(2) was purified from strain No. 7 as an electrophoretically homogeneous protein. Its pI was 9.4. Cytochrome c(2) was reduced by incubating with D-LDH and D-lactate.

Coenzymes↗
PubMed1969

Gene dosage at the lactate dehydrogenase b locus in triploid and diploid teiid lizards.

Triploid parthenogenetic lizards which are heterozygous at the lactate dehydrogenase b locus show approximately two doses of the b allele and approximately one dose of the b' allele. This finding agrees with the triploid karyotype composed of two haploid complements of chromosomes indistinguishable from those of species carrying the b allele and one complement indistinguishable from that of the species which carries the b' allele. Densitometry of electrophoretic patterns of lactate dehydrogenase from heart muscle and from kidney indicates approximately equal expression of each of the b alleles in the triploid lizards. Heterozygouis diploid lizards from the same parthenogenetic species, in agreement with their karyotype, show equal doses of b and b' alleles.

Alleles↗
PubMed1984

Microbiochemical investigation on diurnal rhythmic changes of the activities of the lactate dehydrogenase in the periportal and perivenous zones of the acinus of the rat liver.

Activities of the lactate dehydrogenase within the periportal zone and within the perivenous zone in the first layer of hepatocytes adjacent to terminal hepatic venules and the remainder of the perivenous parenchyma of the liver acinus were measured using a Lowry technique during a full 24-h cycle (08.00-08.00) in untreated adult male Wistar rats kept under 12 h of light and 12 h of darkness, scotophase 18.25-06.25. In all three regions studied a broad first maximum was recorded between 10.00 and 22.00 with the peak value at 16.00 and a high and narrow peak at 24.00. Zonal and intrazonal heterogeneity of the lactate dehydrogenase were retained during the full day and night cycle. The regions displayed individual dynamic changes in enzyme activity.

Animals↗
PubMed1997

Eliminating unnecessary lactate dehydrogenase testing. A utilization review study and national survey.

BACKGROUND: Consensus recommendations call for the elimination of lactate dehydrogenase (LDH) tests from routine rule out myocardial infarction (ROMI) protocols. METHODS: We conducted a utilization review project in which we evaluated the institutional impact of removing LDH and LDH isoenzyme tests from our hospital diagnostic panel. We then conducted a scripted telephone survey of 100 US hospitals to assess the generalizability of this project. RESULTS: All our cardiology staff members supported this intervention. Lactate dehydrogenase isoenzyme test results did not add clinically useful data for any of 200 consecutive patients discharged with a diagnosis of acute myocardial infarction, and selective use of LDH isoenzyme testing in cases where it was clinically believed to be indicated cut costs 99% during the year after our intervention. Furthermore, our telephone survey demonstrated that 66% of US hospitals polled continue to test for LDH isoenzymes in every patient with possible myocardial infarction. CONCLUSIONS: Our results corroborate prior recommendations for the removal of LDH testing from the routine ROMI protocol. Such an intervention may be accomplished easily, with excellent staff acceptance and considerable savings. Most US hospitals continue to include LDH testing in their ROMI panels despite national guidelines recommending otherwise.

Clinical Enzyme Tests↗
PubMed1977

[Serum lactate dehydrogenase activity after renal transplantation (author's transl)].

Regular 4-weekly follow-up controls of serum lactate dehydrogenase activity in 23 renal transplant recipients revealed a constant rise in serum LDH activity during the early postoperative months. During the first post-transplant month serum LDH activity increased from 150.0 +/- 48.2 mE/ml to 195.5 +/- 84.8 mE/ml, serum enzyme activity being highest (329.1 +/- 143.2 mE/ml) 6 months after surgery. Since serum creatinine levels remained relatively constant, it seems unlikely that renal rejection played a major pathogenic role in the production of increased LDH activity. Since the pattern of lactate dehydrogenase isoenzymes was ithin normal limits, the pathogenesis of increased LDH serum activity following renal transplantation is not yet clear. Possible causes such as liver damage due to hepatitis B, macrocytosis induced by immunosuppressive therapy and myopathy to steroids are discussed.

Adult↗
PubMed1996

Non-thermal effects of a ceramics radiation on reversibility of lactate dehydrogenase reaction.

Non-thermal effects of a ceramics radiation on reversibility of lactate dehydrogenase reaction have been investigated using the enzyme irradiated on cooling, and a pyruvate/NADH (system I) or a lactate/NAD+ (system II) as substrate. The Km for lactate in the system II using the irradiated enzyme tended to decrease just like balancing with the increase in Km for pyruvate in system I. The Vmax/Km for system II was increased 2.3-fold by the 18-h irradiated enzyme. Each enthalpy and entropy change in system II using the 18-h irradiation of the enzyme was decreased by 21 kJ mol-1, although that in system I was increased by 12 kJ mol-1. From a thermodynamic analysis, it was estimated that solvation of the active center of LDH was promoted and stabilized by the irradiation, and that it caused this regulation of the reversibility of LDH.

Animals↗
PubMed1981

Reconstitution of the allosteric L-lactate dehydrogenase from Lactobacillus casei investigated by hybridization.

The reassociation process of the urea-denatured allosteric L-lactate dehydrogenase from Lactobacillus casei was investigated by hybridization experiments between the reassociating enzymes from L. casei and Lactobacillus curvatus. The quantitatively evaluated hybridization patterns indicate an assembly pathway from the unfolded subunits to the tetrameric state via dimers. The comparison of the kinetics of reassociation and reactivation of the L. casei L-lactate dehydrogenase shows that the tetramer is the only active form.

Allosteric Regulation↗
PubMed1993

Actions of amiodarone on mitochondrial ATPase and lactate dehydrogenase activities in guinea pig heart preparations.

The effects of amiodarone on mitochondrial ATPase (EC 3.6.1.3) and lactate dehydrogenase (LDH: EC 1.1.1.27) activities were studied in guinea pig mitochondrial preparations in order to test the hypothesis that amiodarone exerts some of its effects as a result of multiple actions on membrane-bound enzymes and receptors. Amiodarone inhibited the ATPase activity in the range of 10 pM to 10 mM (n = 10) with IC50 values of 56.4 +/- 7.2 microM. However, although the inhibitory action was very significant (P < 0.0001, compared to the control) in the concentration range of 100 pM to 10 microM, the differences in individual enzyme responses showed very weak correlation with drug concentration. In this region, the inhibitory effects were almost constant at approximately 37%. Below 100 pM and above this range however, the concentration-response relationships were steep, reaching total inhibition at approximately 2.5 mM. Amiodarone also exerted concentration-dependent inhibitory effects on lactate dehydrogenase activity. However, over the effective inhibitory concentration range (5-95%) of 7.5 microM to 2.5 mM (n = 8) and IC50 value of 108 +/- 6 microM, its inhibitory potency was twofold weaker than that of its ATPase inhibition. We propose that these actions contribute, at least in part, to the mechanism(s) of some of the pharmacological actions of amiodarone.

Adenosine Triphosphatases↗
PubMed1978

Malate dehydrogenase of the cytosol. A kinetic investigation of the reaction mechanism and a comparison with lactate dehydrogenase.

1. The mechanisms of the reduction of oxaloacetate and of 3-fluoro-oxaloacetate by NADH catalysed by cytoplasmic pig heart malate dehydrogenase (MDH) were investigated. 2. One mol of dimeric enzyme produces 1.7+/-0.4 mol of enzyme-bound NADH when mixed with saturating NAD+ and L-malate at a rate much higher than the subsequent turnover at pH 7.5. 3. Transient measurements of protein and nucleotide fluorescence show that the steady-state complex in the forward direction is MDH-NADH and in the reverse direction MDH-NADH-oxaloacetate. 4. The rate of dissociation of MDH-NADH was measured and is the same as Vmax. in the forward direction at pH 7.5. Both NADH-binding sites are kinetically equivalent. The rate of dissociation varies with pH, as does the equilibrium binding constant for NADH. 5. 3-Fluoro-oxaloacetate is composed of three forms (F1, F2 and S) of which F1 and F2 are immediately substrates for the enzyme. The third form, S, is not a substrate, but when the F forms are used up form S slowly and non-enzymically equilibrates to yield the active substrate forms. S is 2,2-dihydroxy-3-fluorosuccinate. 6. The steady-state compound during the reduction of form F1 is an enzyme form that does not contain NADH, probably MDH-NAD+-fluoromalate. The steady-state compound for form F2 is an enzyme form containing NADH, probably MDH-NADH-fluoro-oxaloacetate. 7. The rate-limiting reaction in the reduction of form F2 shows a deuterium isotope rate ratio of 4 when NADH is replaced by its deuterium analogue, and the rate-limiting reaction is concluded to be hydride transfer. 8. A novel titration was used to show that dimeric cytoplasmic malate dehydrogenase contains two sites that can rapidly reduce the F1 form of 3-fluoro-oxaloacetate. The enzyme shows 'all-of-the-sites' behaviour. 9. Partial mechanisms are proposed to explain the enzyme-catalysed transformations of the natural and the fluoro substrates. These mechanisms are similar to the mechanism of pig heart lactate dehydrogenase and this, and the structural results of others, can be explained if the two enzymes are a product of divergent evolution.

Chemical Phenomena↗