Phenolic Azo Dye Oxidation by Laccase from Pyricularia oryzae

Laccase oxidation of phenolic azo dyes was examined with a commercially available laccase from Pyricularia oryzae as the model. Methyl-, methoxy-, chloro-, and nitro-substituted derivatives of 4-(4(prm1)-sulfophenylazo)-phenol were examined as substrates for this laccase. Only the substituents on the phenolic ring were changed. Among the dyes examined, only 2-methyl-, 2-methoxy-, 2,3-dimethyl-, 2,6-dimethyl-, 2,3-dimethoxy-, and 2,6-dimethoxy-substituted 4-(4(prm1)-sulfophenylazo)-phenol served as substrates. Preliminary kinetic studies suggest that 2,6-dimethoxy-substituted 4-(4(prm1)-sulfophenylazo)-phenol is the best substrate. Laccase oxidized the 2,6-dimethyl derivative of 4-(4(prm1)-sulfophenylazo)-phenol to 4-sulfophenylhydroperoxide (SPH) and 2,6-dimethyl-1,4-benzoquinone. The 2-methyl- and 2-methoxy-substituted dyes were oxidized to SPH and either 2-methyl- or 2-methoxy-benzoquinone. Six products were formed from laccase oxidation of the 2,6-dimethoxy-substituted dye. Three of them were identified as SPH, 4-hydroxybenzenesulfonic acid, and 2,6-dimethoxybenzoquinone. A mechanism for the formation of benzoquinone and SPH from laccase oxidation of phenolic azo dyes is proposed. This study suggests that laccase oxidation can result in the detoxification of azo dyes.     

Putative Calmodulin-Binding Domains in Aflatoxin Biosynthesis–Regulatory Proteins

The inhibition of aflatoxin production by trifluoperazine, an anticalmodulin (CaM) agent and the relevance of Ca²⁺/CaM-dependent phosphorylation and dephosphorylation during aflatoxin biosynthesis was previously reported. To identify proteins that may be regulated by CaM, an in silico analysis for putative CaM-binding domains (CaMBDs) in the aflatoxin-related proteins of Aspergillus parasiticus was performed using the CaM target database. Interestingly, the key regulators of aflatoxin biosynthesis such as AflR and AflJ contained predicted CaMBDs at their C-termini. Furthermore, potential phosphorylation sites for CaM-kinase II were present within these CaMBDs. In addition to other aflatoxin biosynthesis enzymes—such as Vbs, DmtA and OmtA, and the VeA protein (known to regulate the expression of AflJ and AflR)—also showed the presence of putative CaMBDs. Although the present report reaffirms earlier observations on CaM-mediated regulation of aflatoxin biosynthesis, it also opens new avenues for identifying the specific targets of CaM and elucidating the exact mechanism of initiation and regulation of aflatoxin biosynthesis.     

Interrelations between oxidative stress and calcineurin in the attenuation of cardiac apoptosis by eugenol

In view of the known involvement of oxidative stress and calcineurin (Ca²⁺-calmodulin dependent protein phosphatase) in β-Adrenergic stimulated events, we examined the influence of eugenol (an antioxidant generally regarded as safe by the Food and Agricultural Organization of the United Nations) on isoproterenol-induced apoptosis in neonatal cardiomyocytes. In comparison to unstimulated controls, cardiomyocytes stimulated with 50 μM isoproterenol for 48 h demonstrated (a) increased intracellular Ca²⁺ levels (b) oxidative stress involving enhanced reactive oxygen species, decreased GSH/GSSG ratio, enhanced lipid peroxidation, increased activities of superoxide dismutase and glutathione peroxidase (c) apoptosis, evidenced by increased number of annexin V/TUNEL positive cells, enhanced membrane fluidity, decreased mitochondrial membrane potential, increased activities of caspase 3 and 9 along with (d) increased calcineurin activity. Pre-incubation of cardiomyocytes with 100 μM eugenol for 1 h, followed by isoproterenol treatment for 48 h, led to reversal of enhanced intracellular Ca²⁺ levels, oxidative stress, calcineurin activation and apoptosis caused by isoproterenol. In addition, similar treatment of cardiomyocytes with 10 nM FK506, a calcineurin inhibitor, could also attenuate isoproterenol-induced apoptosis. These results indicate the beneficial effects of eugenol in preventing cardiomyocyte apoptosis.     

Metabolomic profiling reveals a role for androgen in activating amino acid metabolism and methylation in prostate cancer cells

Prostate cancer is the second leading cause of cancer related death in American men. Development and progression of clinically localized prostate cancer is highly dependent on androgen signaling. Metastatic tumors are initially responsive to anti-androgen therapy, however become resistant to this regimen upon progression. Genomic and proteomic studies have implicated a role for androgen in regulating metabolic processes in prostate cancer. However, there have been no metabolomic profiling studies conducted thus far that have examined androgen-regulated biochemical processes in prostate cancer. Here, we have used unbiased metabolomic profiling coupled with enrichment-based bioprocess mapping to obtain insights into the biochemical alterations mediated by androgen in prostate cancer cell lines. Our findings indicate that androgen exposure results in elevation of amino acid metabolism and alteration of methylation potential in prostate cancer cells. Further, metabolic phenotyping studies confirm higher flux through pathways associated with amino acid metabolism in prostate cancer cells treated with androgen. These findings provide insight into the potential biochemical processes regulated by androgen signaling in prostate cancer. Clinically, if validated, these pathways could be exploited to develop therapeutic strategies that supplement current androgen ablative treatments while the observed androgen-regulated metabolic signatures could be employed as biomarkers that presage the development of castrate-resistant prostate cancer.     

Biological and structural features of murine angiogenin-4, an angiogenic protein

Murine angiogenin-4 (mAng-4) is a member of the pancreatic ribonuclease superfamily that is expressed in some endodermally derived organs. We now show that mAng-4 is angiogenic using a thoracic aorta assay never before applied to the angiogenins. mAng-4, human angiogenin (hAng), and murine angiogenin-1 (mAng-1) stimulate the proliferation of IGR1 melanoma cells but do not stimulate the proliferation or migration of bovine corneal endothelial cells or primary mouse embryonic fibroblasts. In addition, we report the 3-D structure of mAng-4 at 2.02-A resolution. The structure shows that the residues forming the putative B1, P1, and B2 RNA-binding subsites occupy positions similar to their hAng counterparts. The B1 subsite is obstructed by Glu115 and Ile118. The obstruction is stabilized by a novel salt bridge between the C-terminal carboxyl group and the side chain of Arg99. Through mutational studies, we identify residues critical to the angiogenic function of mAng-4. The effect of H12A and H112A mutations in the catalytic site indicates that ribonucleolytic activity is essential to angiogenesis. The consequences of a nearby E115A mutation are consistent with a significant role for Glu115 in the attenuation of enzymatic activity but also suggest that sufficient suppression of catalysis is necessary for angiogenesis. The effect of an R32A mutation in the putative nuclear localization sequence indicates that this residue is crucial for angiogenesis. In the putative cell-binding segment, the replacement of Lys59 with Asn (its counterpart at position 61 of hAng) does not abrogate enzymatic activity but abolishes angiogenic activity, the reason for which is unclear.     

Behavior of endothelial cells on Matrigel and development of a method for a rapid and reproducible in vitro angiogenesis assay

During the process of angiogenesis, the normally quiescent endothelial cells that line the vasculature are induced to proliferate, migrate and align to form new blood vessels by angiogenic stimuli. Assays for angiogenic factors mostly involve in vivo approaches. The two most commonly used in vivo assays—the chick chorioallantoic membrane (CAM) assay and the rabbit corneal assay are tedious to perform and are technically demanding. Several in vitro assays have also been developed, based on the ability of endothelial cells to form tubes in 3-D matrices. Here, we describe the modification of a microcarrier bead-based assay. This assay combines cells grown on Cytodex-3 microcarrier beads with Matrigel to provide an easy, rapid, and reliable method for evaluating and measuring angiogenic activity. We also describe the differential behavior of normal and transformed endothelial cells cultured in Matrigel.     

Immobilization of the fungus, Tolypocladium sp. for the production of Cyclosporin A

The fungus Tolypocladium sp. obtained from the culture collection of VCRC, Pondicherry, was immobilized in calcium alginate and used for the production of Cyclosporin A in a packed bed reactor under batch and continuous flow modes. The precursor amino acids, L-valine and L-leucine increased the yield of Cyc A when added individually; however when added together, the increase in the yield was no better than as added individually. The half-life of the biocatalyst was found to be around six months.     

Language cannot be reduced to biology: Perspectives from neuro-developmental disorders affecting language learning

The study of language knowledge guided by a purely biological perspective prioritizes the study of syntax. The essential process of syntax is recursion — the ability to generate an infinite array of expressions from a limited set of elements. Researchers working within the biological perspective argue that this ability is possible only because of an innately specified genetic makeup that is specific to human beings. Such a view of language knowledge may be fully justified in discussions on biolinguistics, and in evolutionary biology. However, it is grossly inadequate in understanding language-learning problems, particularly those experienced by children with neurodevelopmental disorders such as developmental dyslexia, Williams syndrome, specific language impairment and autism spectrum disorders. Specifically, syntax-centered definitions of language knowledge completely ignore certain crucial aspects of language learning and use, namely, that language is embedded in a social context; that the role of envrironmental triggering as a learning mechanism is grossly underestimated; that a considerable extent of visuo-spatial information accompanies speech in day-to-day communication; that the developmental process itself lies at the heart of knowledge acquisition; and that there is a tremendous variation in the orthographic systems associated with different languages. All these (socio-cultural) factors can influence the rate and quality of spoken and written language acquisition resulting in much variation in phenotypes associated with disorders known to have a genetic component. Delineation of such phenotypic variability requires inputs from varied disciplines such as neurobiology, neuropsychology, linguistics and communication disorders. In this paper, I discuss published research that questions cognitive modularity and emphasises the role of the environment for understanding linguistic capabilities of children with neuro-developmental disorders. The discussion pertains to two specific disorders, developmental dyslexia and Williams syndrome.     

THE EFFECT OF ELECTRICAL STIMULATION AND HIGH POTASSIUM CONCENTRATIONS ON THE EFFLUX OF [3H] γ-AMINOBUTYRIC ACID FROM BRAIN SLICES

Abstract— Brain slices were incubated with [³H]GABA in a medium containing aminooxyacetic acid to prevent metabolism of [³H]GABA by GABA-glutamate transaminase. The slices, which rapidly accumulated radioactivity, were then continuously perfused and the efflux of [³H]GABA from the tissue was measured. The spontaneous efflux of [³H]GABA consisted of an initial rapid phase followed by a much slower release of [³[H]GABA. After 40 min perfusion 90 per cent of the radioactivity remained in the tissue.
The slices were depolarized by electrical stimulation or by perfusion with a medium containing a high potassium concentration (40 mM). These procedures caused a striking increase in the efflux of [³H]GABA. The increased efflux produced by potassium, but not that produced by electrical stimulation, was dependent on calcium ions in the medium. The effect of electrical stimulation on [³H]GABA release was considerably reduced by a raised concentration (10 mM) of magnesium in the medium.
High potassium concentrations and electrical stimulation did not cause an increase in the efflux of [¹⁴C]urea, L-[³H]leucine or [¹⁴C]α-amino-isobutyric acid from brain slices. These results are consistent with the suggestion that GABA may be an inhibitory transmitter in the cerebral cortex.