Asymmetric Synthesis of N-Alkyl Amino Acids through a Biocatalytic Dynamic Kinetic Resolution of PEGylated N-Alkyl Amino Esters

The first examples of a practical procedure for a lipase-catalyzed dynamic kinetic resolution of PEGylated N-alkyl amino esters is reported. This method allows for the preparation of a broad range of aromatic and aliphatic enantiomerically enriched N-alkyl unnatural amino acids in up to 98% yield and 99% ee. We have found that PEGylated esters have a significant solubility advantage and improved reactivity over traditional hydrophobic lipase substrates, thereby allowing for efficient and scalable dynamic kinetic resolution (DKR) under aqueous conditions.

High throughput assay for evaluation of reactive carbonyl scavenging capacity

Many carbonyl species from either lipid peroxidation or glycoxidation are extremely reactive and can disrupt the function of proteins and enzymes. 4-hydroxynonenal and methylglyoxal are the most abundant and toxic lipid-derived reactive carbonyl species. The presence of these toxics leads to carbonyl stress and cause a significant amount of macromolecular damages in several diseases. Much evidence indicates trapping of reactive carbonyl intermediates may be a useful strategy for inhibiting or decreasing carbonyl stress-associated pathologies. There is no rapid and convenient analytical method available for the assessment of direct carbonyl scavenging capacity, and a very limited number of carbonyl scavengers have been identified to date, their therapeutic potential being highlighted only recently. In this context, we have developed a new and rapid sensitive fluorimetric method for the assessment of reactive carbonyl scavengers without involvement glycoxidation systems. Efficacy of various thiol- and non-thiol-carbonyl scavenger pharmacophores was tested both using this screening assay adapted to 96-well microplates and in cultured cells. The scavenging effects on the formation of Advanced Glycation End-product of Bovine Serum Albumin formed with methylglyoxal, 4-hydroxynonenal and glucose-glycated as molecular models were also examined. Low molecular mass thiols with an α-amino-β-mercaptoethane structure showed the highest degree of inhibitory activity toward both α,β-unsaturated aldehydes and dicarbonyls. Cysteine and cysteamine have the best scavenging ability toward methylglyoxal. WR-1065 which is currently approved for clinical use as a protective agent against radiation and renal toxicity was identified as the best inhibitor of 4-hydroxynonenal.

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We describe a rapid method for assessment of reactive carbonyl scavengers.

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We evaluated the carbonyl scavenger activity of various pharmacophores.

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α-amino-β-mercaptoethane structure showed the highest degree of activity.

Pandemic influenza A(H1N1) 2009 breakthrough infections and estimates of vaccine effectiveness in Germany 2009-2010

During the 2009 influenza pandemic, a monovalent AS03-adjuvanted vaccine was almost exclusively used in Germany for immunisation against the 2009 pandemic influenza A(H1N1) virus. One-dose vaccination was recommended for all age groups. We applied the screening method for the rapid assessment of vaccine effectiveness (VE) based on reported data of vaccinated and unvaccinated pandemic influenza cases and vaccination coverage estimates. Preliminary results demonstrate excellent VE in persons aged 14-59 years (96.8%; 95% confidence interval (CI): 95.2-97.9) and moderately high VE in those 60 years or older (83.3%; 95% CI: 71.0-90.5).

Phenolic extracts from various Algerian plants as strong inhibitors of porcine liver carboxylesterase

Carboxylesterases (CE), expressed at high levels in human liver and intestine, are thought to detoxify xenobiotics. The goal of this study was to study the effect of phenolic compounds from several plants from the Algerian Atlas used traditionally in Arab folk medicine on the enzymatic activity of porcine liver carboxylesterase. The plants have shown a potent inhibition of carboxylesterase (CE) enzymatic activity in a concentration-dependent manner. Results indicate that the Phenolic extracts from these plants lead to the inactivation of the CE pI = 5.1 with K(i) values in micromolar range (1.4-38 microM). These results encourage further biological investigation and identification the inhibitors responsible for this activity.

Effect of flavonoids from various Mediterranean plants on enzymatic activity of intestinal carboxylesterase

Flavonol compounds of three Mediterranean plants from the Algerian Atlas used traditionally in Arab folk medicine, Arenaria serpyllifolia, Rhamnus alaternus and Thapsia garganica, were found to inhibit the enzymatic activities of both rat intestine and purified porcine liver carboxylesterase in a concentration-dependent manner. Results indicate that the flavonol compounds from the aerial part of these plants lead to the inactivation of the CE pI = 5.1 with Ki of micromolar range. These results encourage us to perform further biological investigation.

Maackiain 3-O-(6′-O-malonyl-β-D-glucopyranoside) from Oudneya africana, a powerful inhibitor of porcine kidney acylase I

The inhibitory effect of phenolic extracts of several plants from the Algerian Atlas used traditionally in Arab folk medicine was tested on the porcine kidney acylase I activity. An endemic Saharan plant of the Brassicaceae family, Oudneya africana, has shown a strong inhibitory effect. The active compound was isolated and purified by semi-preparative HPLC and HPLC-photodiode array detection, and structurally determined using 1H, 13C NMR and mass spectroscopy methods. Results indicate that maackiain 3-O-(6'-O-malonyl-beta-D-glucopyranoside) showed a competitive inhibition of porcine kidney acylase I with a Ki value of 11 microM. The malonyl moiety appeared to be a structural key element for the inhibitory activity. This observation indicates interesting structure-activity relationships for the inhibitory action of this compound on the acylase I and its potential role in the toxicity of haloalkene-derived mercapturates and that of the enzyme in detoxication and bioactivation.

Autosomal dominant GH deficiency due to an Arg183His GH-1 gene mutation: clinical and molecular evidence of impaired regulated GH secretion

G to A transition at position 6664 of the GH-1 gene results in the substitution of Arg183 by His (R183H) in human GH protein and causes a new form of autosomal dominant isolated GH deficiency (type II). Although a weak GH release after standard pharmacological provocation tests is observed in these affected individuals, the dominant inheritance pattern is postulated to be caused by a blockade of the GH-regulated secretion in the somatotrophs. The aim of this study was to analyze the impact of this autosomal dominant mutation not only at a clinical, but also at a cellular, level. The results of the different stimulation tests showed first that the patient possesses a severely impaired, but releasable, GH store, and second that the GH secretion is blocked in a time-dependent and reversible way. To confirm these clinical data, cell culture studies were performed looking at the regulated secretory pathway of GH using AtT-20 cells. Importantly, we were able to show that when the R183H mutant GH was expressed in AtT-20 cells, secretagogue (forskolin) induced a normal R183H GH-regulated secretion, but in AtT-20 cells coexpressing both the R183H mutant GH and the normal GH, forskolin-induced GH secretion was markedly reduced. Together, the experiments seem to support the hypothesis that R183H mutant GH severely impaired the GH-regulated secretion and may, therefore, be the cause of this specific form of isolated GH deficiency type II.

[Oxidative stress and human disease. Current knowledge and perspectives for prevention]

DYNAMIC BALANCE: The antibiotic status of the human organism results from the dynamic balance between the antioxidant system and the production of reactive oxygen species. Oxidative stress occurs when this balance shifts in favor of pro-oxidants as can occur in several disease situations. ROS: Part of the oxygen used by cells is transformed into toxic metabolites, reactive oxygen species (ROS), which can be the cause or consequence of tissue and molecular disorders. Some of the most prominent diseases linked with oxidative stress include atherosclerosis, cancer, allergy, neurodegenerative diseases, Parkinson's disease. PERSPECTIVES FOR PREVENTION: Actions designed to prevent the environmental cause, such as eviction of a exposure to toxins or a change in eating habits, can be an effective means of reducing the lesions induced. Study of total antioxidant potential could be quite useful for detecting and monitoring environmental damage and for clinical follow-up. It could also help in determining, for each individual, the negative or positive development of a therapy on the anti-free radical action. Treatments must be personalized according to the tested response.

Analysis of drug transport and metabolism in cell monolayer systems that have been modified by cytochrome P4503A4 cDNA-expression

Human CYP3A4, the major human, intestinal, drug metabolizing cytochrome P450, has been introduced into three mammalian cell lines (Caco-2, MDCK and LLC-PK1) suitable for making drug permeability measurements. The levels and stability of expression were analyzed by enzyme assays (testosterone 6beta-hydroxylase and nifedipine oxidase). Long term, stable CYP3A4 expression/cell growth rate was obtained in MDCK cells. In the LLC-PK1 system, shorter term, stable expression was achieved. However, in Caco-2 cells, derivatives with better properties than those previously reported could not be obtained. The highest level of CYP3A4 catalytic activity was obtained in LLC-PK1 cells. In this system, CYP3A4 activity levels appeared comparable to median level human intestinal microsomes. Metabolite formation and inhibition kinetics were examined in cell monolayers. Nifedipine was found to be extensively metabolized (19%) during passage across cell monolayers. In general, affinity related parameters (apparent Km and apparent Ki) were 1.5- to three-fold higher under conditions of flux through the monolayers relative to steady-state conditions. These systems should be useful for examining the role of intestinal CYP3A4 in first-pass metabolism and drug-drug interactions.

CYP3A4 allelic variants with amino acid substitutions in exons 7 and 12: evidence for an allelic variant with altered catalytic activity

OBJECTIVE

To determine the existence of mutant and variant CgammaP3A4 alleles in three racial groups and to assess functions of the variant alleles by complementary deoxyribonucleic acid (cDNA) expression.

METHODS

A bacterial artificial chromosome that contains the complete CgammaP3A4 gene was isolated and the exons and surrounding introns were directly sequenced to develop primers to polymerase chain reaction (PCR) amplify and sequence the gene from lymphocyte DNA. DNA samples from Chinese, black, and white subjects were screened. Mutating the affected amino acid in the wild-type cDNA and expressing the variant enzyme with use of the baculovirus system was used to functionally evaluate the variant allele having a missense mutation.

RESULTS

To investigate the existence of mutant and variant CgammaP3A4 alleles in humans, all 13 exons and the 5'-flanking region of the human CgammaP3A4 gene in three racial groups were sequenced and four alleles were identified. An A-->G point mutation in the 5'-flanking region of the human CgammaP3A4 gene, designated CgammaP3A4*1B, was found in the three different racial groups. The frequency of this allele in a white population was 4.2%, whereas it was 66.7% in black subjects. The CgammaP3A4*1B allele was not found in Chinese subjects. A second variant allele, designated CgammaP3A4*2, having a Ser222Pro change, was found at a frequency of 2.7% in the white population and was absent in the black subjects and Chinese subjects analyzed. Baculovirus-directed cDNA expression revealed that the CYP3A4*2 P450 had a lower intrinsic clearance for the CYP3A4 substrate nifedipine compared with the wild-type enzyme but was not significantly different from the wild-type enzyme for testosterone 6beta-hydroxylation. Another rare allele, designated CgammaP3A4*3, was found in a single Chinese subject who had a Met445Thr change in the conserved heme-binding region of the P450.

CONCLUSIONS

These are the first examples of potential function polymorphisms resulting from missense mutations in the CgammaP3A4 gene. The CgammaP3A4*2 allele was found to encode a P450 with substrate-dependent altered kinetics compared with the wild-type P450.

A point about electron paramagnetic resonance detection of irradiated foodstuffs

This paper makes a point about the identification of irradiated foodstuffs by means of electron paramagnetic resonance (EPR) or electron spin resonance (ESR). EPR is the most accurate method for such routine applications since radicals are stabilised for a long time in all (or part of) foods that are in solid and dry states; consequently, EPR can be applied to meat and fish bones, fruit and relative products (from vegetal origin). More details are given for mollusc shells, such as oysters and mussels.

Fate of the junction phosphate in alternating forward and reverse self-splicing reactions of group II intron RNA

The RNA-catalysed self-splicing reaction of group II intron RNA is assumed to proceed by two consecutive transesterification steps, accompanied by lariat formation. This is effectively analogous to the small nuclear ribonucleoprotein (snRNP)-mediated nuclear pre-mRNA splicing process. Upon excision from pre-RNA, a group II lariat intervening sequence (IVS) has the capacity to re-integrate into its cognate exons, reconstituting the original pre-RNA. The process of reverse self-splicing is presumed to be a true reversion of both transesterification steps used in forward splicing. To investigate the fate of the esterified phosphate groups in splicing we assayed various exon substrates (5'E-*p3'E) containing a unique 32P-labelled phosphodiester at the ligation junction. In combined studies of alternating reverse and forward splicing we have demonstrated that the labelled phosphorus atom is displaced in conjunction with the 3' exon from the ligation junction to the 3' splice site and vice versa. Neither the nature of the 3' exon sequence nor its sequence composition acts as a prominent determinant for both substrate specificity and site-specific transesterification reactions catalysed by bI1 IVS. A cytosine ribonucleotide (pCp; pCOH) or even deoxyoligonucleotides could function as an efficient substitute for the authentic 3' exon in reverse and in forward splicing. Furthermore, the 3' exon can be single monophosphate group. Upon incubation of 3' phosphorylated 5' exon substrate (5'E-*p) with lariat IVS the 3'-terminal phosphate group is transferred in reverse and forward splicing like an authentic 3' exon, but with lower efficiency. In the absence of 3' exon nucleotides, it appears that substrate specificity is provided predominantly by the base-pairing interactions of the intronic exon binding site (EBS) sequences with the intron binding site (IBS) sequences in the 5' exon. These studies substantiate the predicted transesterification pathway in forward and reverse splicing and extend the catalytic repertoire of group II IVS in that they can act as a potential and sequence-specific transferase in vitro.