Cationic polyelectrolytes prevent the aggregation of l-lactate dehydrogenase under unstable conditions

Unstructured biological macromolecules have attracted attention as protein aggregation inhibitors in living cells. Some are characterized by their free structural configuration, highly charged, and water-soluble. However, the importance of these properties in inhibiting protein aggregation remains unclear. In this study, we investigated the effect of charged poly (amino acids), which mimic these properties, on aggregation of l-lactate dehydrogenase (LDH) and compared their effects to monomeric amino acids and folded proteins. LDH was stable and active at a neutral pH (~7) but formed inactive aggregates at acidic pH (< 6). Adding cationic polyelectrolytes of poly-l-lysine and poly-l-arginine suppressed the acid-induced aggregation and inactivation of LDH under acidic pH values. Adding monomeric amino acids and cationic folded proteins also prevented LDH aggregation but with lower efficacy than cationic polyelectrolytes. These results indicate that unstructured polyelectrolytes effectively stabilize unstable enzymes because they interact flexibly and multivalently with them. Our findings provide a simple method for stabilizing enzymes under unstable conditions.

Hematological profile and biochemical markers of COVID-19 non-survivors: A retrospective analysis

Background

Coronavirus disease is primarily transmitted through the respiratory route and bodily contact. The fatality in COVID-19 cases was alarming in the initial days. This study analyzes hematological and biochemical markers of COVID-19 non-survivors.

Material and methods

In this single-center study, records of 249 patients hospitalized with COVID-19 were studied for hematological profile and biochemical markers. Records of patients with laboratory-confirmed COVID-19 disease hospitalized between April 14, 2020, to August 15, 2020, were included in the analysis.

Results

Significantly, the disease mortality was associated with increased procalcitonin (P < 0.05), C-reactive protein (P < 0.05), aspartate transaminase (P < 0.05), serum potassium (P < 0.05), neutrophils count (P < 0.05), white blood cell count (P < 0.05), prothrombin time (P < 0.05) and activated prothrombin time (P < 0.05) in patients reported abnormal x-ray findings. Further, patients with abnormal radiological findings significantly showed a reduced level of lymphocyte counts (P < 0.05), oxygen saturation (P < 0.05), and partial oxygen pressure (P < 0.05). Reduced level of aspartate aminotransferase (P < 0.05), alanine aminotransferase (P < 0.05) and lactate dehydrogenase (P < 0.05) reported significant association with mortality among patients with COVID-19.

Conclusions

The clinicians may consider the hematological and biochemical parameters in the patients with COVID-19 in future decision-making. These indicators might support clinical decisions to identify high fatality cases and poor diagnosis in the initial admission phase. In COVID-19 patients, we recommend close monitoring on procalcitonin, C-reactive protein, neutrophils count, and white blood cell count as a clinical indicator for potential progression to critical illness.

Rational engineering of the Plasmodium falciparuml-lactate dehydrogenase loop involved in catalytic proton transfer to improve chiral 2-hydroxybutyric acid production

l-lactate dehydrogenases (LDHs) has been widely studied for their ability to reduce 2-keto acids for the production of 2-hydroxy acids, whereby 2-hydroxybutyric acids (2-HBA) is among the most important fundamental building blocks for synthesizing pharmaceuticals and biodegradable materials. However, LDHs usually show low activity towards 2-keto acids with longer side chain such as 2-oxobutyric acid (2-OBA). Here rational engineering of the Plasmodium falciparum LDH loop with residue involved in the catalytic proton transfer was initially studied. By combining homology alignment and structure-based design approach, we found that changing the charge characteristics or hydrogen bond network interactions of this loop could improve enzymatic catalytic activities and stabilities towards 2-OBA. Compared with wild type, variant N197D_ldh showed 1.15 times higher activity and 2.73 times higher K_cat/Km. The half-life of variant N197D_ldh at 40 °C increased to 77.9 h compared with 50.4 h of wild type. Furthermore, asymmetric synthesis of (S)-2-HBA with coenzyme regeneration revealed 95.8 g/L production titer within 12 h for variant N197D_ldh, 2.05 times higher than using wild type. Our study indicated the importance of loop with residues involved in the catalytic proton transfer process, and the engineered LDH would be more suitable for (S)-2-HBA production.

One step open fermentation for lactic acid production from inedible starchy biomass by thermophilic Bacillus coagulans IPE22

The aim of this study was to establish a simplified operational process for lactic acid (LA) production by Bacillus coagulans IPE22 from inedible starchy biomass with open fermentation method. First, 29.47 mU/mg specific amylase activity was detected in direct batch fermentation from soluble starch, but the activity of the produced amylase was too low for effective production of LA. Then seven batches from 72 g/L soluble starch were conducted without sterilization. It was found that one step simultaneous liquefaction, saccharification and fermentation (SLSF) with the addition of mesothermal α-amylase and glucoamylase was the optimal mode with LA concentration, yield and productivity of 68.72 g/L, 0.99 g/g and 1.72 g/L h respectively. Finally, inedible starchy biomass, cassava and sorghum flours, were proved to be alternatives to refined soluble starch. For the first time, one step open SLSF of inedible starchy biomass was reported for LA production by B. coagulans.

Promising efficacy of SHR-1210, a novel anti-programmed cell death 1 antibody, in patients with advanced gastric and gastroesophageal junction cancer in China

BACKGROUND

The clinical response to anti-programmed cell death 1 (PD-1) antibodies in patients with advanced gastric and gastroesophageal junction (GEJ) cancer in China has not been reported.

METHODS

This study evaluated the efficacy and safety of SHR-1210, an anti-PD-1 antibody, in patients with advanced gastric/GEJ cancer in a phase 1 trial. The associations between candidate biomarkers (programmed death ligand 1 [PD-L1] expression, mismatch repair status, tumor mutation load, and lactate dehydrogenase [LDH] levels) and the efficacy of SHR-1210 were also explored.

RESULTS

Thirty patients with recurrent or metastatic gastric/GEJ adenocarcinoma who were refractory or intolerant to previous chemotherapy were enrolled between June 2, 2016, and June 8, 2017. Seven patients (23.3%) demonstrated objective responses, including 1 complete response. The objective response rates for patients with PD-L1-positive and PD-L1-negative tumors were 23.1% (3 of 13) and 26.7% (4 of 15), respectively (P = 1.000). Two treatment-related grade 3 or higher adverse events were reported: one was grade 3 pruritus, and the other (3.3%) was grade 5 interstitial lung disease. All 20 patients tested for the mismatch repair status had mismatch repair-proficient tumors, and the response rate was 30.0% (95% confidence interval, 11.9%-54.3%). Patients with a higher mutation load (4 of 10) tended to have better responses than those with fewer mutations (2 of 10), but the difference was not significant (P = .628). Patients with a >10% relative increase from the baseline LDH level were more likely to experience disease progression (90% [9 of 10]) than patients with a ≤10% change (40% [8 of 20]; P = .017).

CONCLUSIONS

Anti-PD-1 antibody SHR-1210 shows encouraging efficacy in patients with advanced gastric/GEJ cancer in China, including mismatch repair-proficient subgroups.

Relative catalytic efficiencies and transcript levels of three d- and two l-lactate dehydrogenases for optically pure d-lactate production in Sporolactobacillus inulinus

As the optical purity of the lactate monomer is pivotal for polymerization, the production of optically pure d‐lactate is of significant importance. Sporolactobacillus inulinus YBS1‐5 is a superior optically pure d‐lactate‐producing bacterium. However, little is known about the relationship between lactate dehydrogenases in S. inulinus YBS1‐5 and the optical purity of d‐lactate. Three potential d‐lactate dehydrogenase (D‐LDH1‐3)‐ and two putative l‐lactate dehydrogenase (L‐LDH1‐2)‐encoding genes were cloned from the YBS1‐5 strain and expressed in Escherichia coli D‐LDH1 exhibited the highest catalytic efficiency toward pyruvate, whereas two L‐LDHs showed low catalytic efficiency. Different neutralizers significantly affected the optical purity of d‐lactate produced by strain YBS1‐5 as well as the transcription levels of ldhDs and ldhLs. The high catalytic efficiency of D‐LDH1 and elevated ldhD1 mRNA levels suggest that this enzyme is essential for d‐lactate synthesis in S. inulinus YBS1‐5. The correlation between the optical purity of d‐lactate and transcription levels of ldhL1 in the case of different neutralizers indicate that ldhL1 is a key factor affecting the optical purity of d‐lactate in S. inulinus YBS1‐5.

The occurrence of l-lactate dehydrogenase in the inner mitochondrial compartment of pig liver

Although pig represents a model species in biomedical research including studies dealing with liver patho-physiology, some aspects of liver metabolism need to be addressed. In particular, whether and how pig mitochondria can metabolize l-lactate remains to be established. We show here that pig liver mitochondria (PLM) possess their own l-lactate dehydrogenase (mL-LDH). This was shown both via immunological analysis and by assaying photometrically the L-LDH reaction in solubilised PLM. The mL-LDH reaction shows hyperbolic dependence on the substrate concentration, it is inhibited by oxamate and proves to differ from the cytosolic activity (cL-LDH), as revealed by the difference found in both pH profiles and temperature dependence of m- and cL-LDH. Titration experiments with digitonin show that mL-LDH is restricted in mitochondrial inner compartment. In agreement with the above findings, three genes in Sus scrofa genome encoded for L-LDH subunits which are predicted to have mitochondrial localization, as investigated by Target P 1.1 and PredSL analysis.

A role for glutamate-333 of Saccharomyces cerevisiae cystathionine γ-lyase as a determinant of specificity

Cystathionine γ-lyase (CGL) catalyzes the hydrolysis of l-cystathionine (l-Cth), producing l-cysteine (l-Cys), α-ketobutyrate and ammonia, in the second step of the reverse transsulfuration pathway, which converts l-homocysteine (l-Hcys) to l-Cys. Site-directed variants substituting residues E48 and E333 with alanine, aspartate and glutamine were characterized to probe the roles of these acidic residues, conserved in fungal and mammalian CGL sequences, in the active-site of CGL from Saccharomyces cerevisiae (yCGL). The pH optimum of variants containing the alanine or glutamine substitutions of E333 is increased by 0.4-1.2 pH units, likely due to repositioning of the cofactor and modification of the pKa of the pyridinium nitrogen. The pH profile of yCGL-E48A/E333A resembles that of Escherichia coli cystathionine β-lyase. The effect of substituting E48, E333 or both residues is the 1.3-3, 26-58 and 124-568-fold reduction, respectively, of the catalytic efficiency of l-Cth hydrolysis. The Km(l-Cth) of E333 substitution variants is increased ~17-fold, while Km(l-OAS) is within 2.5-fold of the wild-type enzyme, indicating that residue E333 interacts with the distal amine moiety of l-Cth, which is not present in the alternative substrate O-acetyl-l-serine. The catalytic efficiency of yCGL for α,γ-elimination of O-succinyl-l-homoserine (kcat/Km(l-OSHS)=7±2), which possesses a distal carboxylate, but lacks an amino group, is 300-fold lower than that of the physiological l-Cth substrate (kcat/Km(l-Cth)=2100±100) and 260-fold higher than that of l-Hcys (kcat/Km(l-Hcys)=0.027±0.005), which lacks both distal polar moieties. The results of this study suggest that the glutamate residue at position 333 is a determinant of specificity.

An abundant LEA protein in the anhydrobiotic midge, PvLEA4, acts as a molecular shield by limiting growth of aggregating protein particles

LEA proteins are found in anhydrobiotes and are thought to be associated with the acquisition of desiccation tolerance. The sleeping chironomid Polypedilum vanderplanki, which can survive in an almost completely desiccated state throughout the larval stage, accumulates LEA proteins in response to desiccation and high salinity conditions. However, the biochemical functions of these proteins remain unclear. Here, we report the characterization of a novel chironomid LEA protein, PvLEA4, which is the most highly accumulated LEA protein in desiccated larvae. Cytoplasmic-soluble PvLEA4 showed many typical characteristics of group 3 LEA proteins (G3LEAs), such as desiccation-inducible accumulation, high hydrophilicity, folding into α-helices on drying, and the ability to reduce aggregation of dehydration-sensitive proteins. This last property of LEA proteins has been termed molecular shield function. To further investigate the molecular shield activity of PvLEA4, we introduced two distinct methods, turbidity measurement and dynamic light scattering (DLS). Turbidity measurements demonstrated that both PvLEA4, and BSA as a positive control, reduced aggregation in α-casein subjected to desiccation and rehydration. However, DLS experiments showed that a small amount of BSA relative to α-casein increased aggregate particle size, whereas PvLEA4 decreased particle size in a dose-dependent manner. Trehalose, which is the main heamolymph sugar in most insects but also a protectant as a chemical chaperone in the sleeping chironomid, has less effect on the limitation of aggregate formation. This analysis suggests that molecular shield proteins function by limiting the growth of protein aggregates during drying and that PvLEA4 counteracts protein aggregation in the desiccation-tolerant larvae of the sleeping chironomid.

The role of the lactate dehydrogenase and the effect of prone position during ventilator-induced lung injury

To examine the impact of lactate dehydrogenase (LDH) as an early marker of ventilator-induced lung injury (VILI) and the effect of prone position during the VILI, we ventilated 28 normal white rabbits (10 supine, 10 prone, 8 controls) for 6 hr or until PaO2/FIO2 ratio was<200 mmHg. We applied an identical injurious ventilatory pattern (peak inspiratory pressure of 35 cmH2O with a PEEP of 3 cmH2O, I:E ratio of 1:2, and FIO2 of 0.40) in the supine and prone group. VILI was assessed by oxygenation, gravimetric analysis and histologic grading. Serum levels of LDH progressively increased significantly during the VILI (supine and prone groups) as compared with controls. There was a significant negative correlation between oxygenation and LDH levels (r=-0.619, p<0.001). Wet weight/dry weight ratios (WW/DW) and histologic scores for dependent regions were significantly higher in the supine than the prone group. There were no differences in WW/DW and histologic scores for nondependent regions between the supine and prone group. These findings suggest that serum LDH levels might be an early marker of severity of lung injury. The prone position resulted in a less severe and more homogenous distribution of VILI.