L-lactate dehydrogenase activity

About: L-lactate dehydrogenase activity is a research topic. Over the lifetime, 7 publications have been published within this topic receiving 135 citations.

Oxygen-labile l(+) lactate-dehydrogenase activity in desulfovibrio-desulfuricans

Abstract: Lactate is the most commonly employed energy substrate for the growth of sulfate-reducing bacteria [1], except for some of the recently discovered new types [2]. Both isomeric forms of lactate are utilized and metabolized to acetate and CO 2. Very little is known about the first enzyme involved in the oxidation of lactate. An N A D + independent membrane-bound L(+) lactate hydrogenase (LDH) activity has been reported in extracts of Desulfovibrio gigas but further details are not available [3]. D(--) L D H was recently detected in Desulfovibrio desulfuricans [4] and Desulfovibrio vulgaris [5]. This enzyme was partially purified and retained its activity without special precautions. Both D(--) LDHs were membranebound, NAD(P)+independent and could be assayed with 2,6-dichlorophenolindophenol (DCPIP) as an artificial electron acceptor. The identity of the in vivo elec'tron acceptors of the LDHs remains to be established with certainty; the D(--) L D H of D. vulgaris could be coupled to cytochrome c553 which is also thought to be the acceptor of the formate dehydrogenase [5]. In this paper we report the presence of high activities of a membrane bound NAD(P) + independent L( + ) L D H in a D. desulfuricans strain. This enzyme was fairly stable when kept anaerobically but extremely unstable in the presence of oxygen. Data on the conditions required for reactivation of oxygen-inactivated enzyme activity in extracts are given. Only very low activities of D(--) L D H were detected despite the fact that our strain grows well oh both L (+ ) and D ) lactate.

Oxidant stress in Neisseria gonorrhoeae: adaptation and effects on L-(+)-lactate dehydrogenase activity.

Abstract: Neisseria gonorrhoeae, an obligate human pathogen, is subjected to oxidant stress when attacked by O2 reduction products formed by neutrophils. In this study, exposure of gonococci to sublethal concentrations of superoxide and hydrogen peroxide (and related O-centered radicals) resulted in phenotypic resistance to oxidant stress. Adaptation required new protein formation but was not related to increases in superoxide dismutase or catalase. We have previously demonstrated that gonococci use phagocyte-derived L-(+)-lactate. Oxidant stress of greater magnitude than that required for adaptation led to a generalized increase in bacterial metabolism, particularly in L-(+)- and D-(-)-lactate utilization and lactate dehydrogenase activity. Increased lactate utilization required new protein synthesis. These results suggest the possibility that lactate metabolism is of importance to N. gonorrhoeae subjected to oxidant stress. Use of lct mutant organisms unable to use L-(+)-lactate should allow examination of this hypothesis.

An absolute requirement of fructose 1,6-bisphosphate for the Lactobacillus casei L-lactate dehydrogenase activity induced by a single amino acid substitution.

Abstract: Lactobacillus casei allosteric L-lactate dehydrogenase (L-LDH) absolutely requires fructose 1,6-bisphosphate [Fru(1,6)P 2 ] for its catalytic activity under neutral conditions, but exhibits marked catalytic activity in theabsence of Fru(1,6)P 2 under acidic conditions through the homotropic activation effect of substrate pyruvate. In this enzyme, a single amino acid replacement, i.e. that of His205 conserved in the Fru(1,6)P 2 -binding site of certain allosteric L-LDHs of lactic acid bacteria with Thr, did not induce a marked loss of the activation effect of Fru(1,6)P 2 or divalent metal ions, which are potent activators that improve the activation function of Fru(1,6)P 2 under neutral conditions. However, this replacement induced a great loss of the Fru(1,6)P 2 -independent activation effect of pyruvate or pyruvate analogs under acidic conditions, consequently indicating an absolute Fru(1,6)P 2 requirement for the enzyme activity. The replacement also induced a significant reduction in the pH-dependent sensitivity of the enzyme to Fru(1,6)P 2 , through a slight decrease and increase of the Fru(1,6)P 2 sensitivity under acidic and neutral conditions, respectively, indicating that His205 is also largely involved in the pH-dependent sensitivity of L.casei L-LDH to Fru(1,6)P 2 . The role of His205 in the allosteric regulation of the enzyme is discussed on the basis of the known crystal structures of L-LDHs.

Low intensity microwave radiation as modulator of the L-lactate dehydrogenase activity.

Abstract: In this study, we investigated experimentally the possibility of modulating protein activity by low intensity microwaves by measuring alternations of l-Lactate Dehydrogenase enzyme (LDH) activity. The LDH enzyme solutions were irradiated by microwaves of the selected frequencies and powers using the Transverse Electro-Magnetic (TEM) cell. The kinetics of the irradiated LDH was measured by continuous monitoring of nicotine adenine dinucleotide, reduced (NADH) absorbance at 340 nm. A comparative analysis of changes in the activity of the irradiated LDH enzyme versus the non-radiated enzyme was performed for the selected frequencies and powers. It was found that LDH activity can be selectively increased only by irradiation at the particular frequencies of 500 MHz [electric field: 0.02 V/m (1.2 × 10−6 W/m2)–2.1 V/m (1.2 × 10−2 W/m2)] and 900 MHz [electric field: 0.021–0.21 V/m (1.2 × 10−4 W/m2)]. Based on results obtained it was concluded that LDH enzyme activity can be modulated by specific frequencies of low power microwave radiation. This finding can serve to support the hypothesis that low intensity microwaves can induce non-thermal effects in bio-molecules.

Bioluminescent flow sensors: L-lactate dehydrogenase activity determination in serum.

Abstract: The catalytic activity of serum L-lactate dehydrogenase (LDH), was determined by monitoring the NADH produced by LDH with bacterial bioluminescent enzymes immobilized on a nylon coil. The LDH reaction of L-lactate with NAD took place in a flow-through mixing coil that preceded the bioluminescent detector coil. The response was linear from 1 to 5000 U/l at 37 degrees C and from 3 to 2000 U/l at 25 degrees C. The intra- and inter-assay reproducibility (CV%) were less than 10% and recovery range was 92% to 110%. The results agreed well with those obtained with a spectrophotometric method.