Screening and statistical optimization of media ingredients for production of microbial transglutaminase

<p>Transglutaminase is a calcium dependent enzyme that catalyses acyl transfer reactions between primary amino groups and protein bound glutamine residues. Eighteen bacterial and twenty eight actinomycetes were screened for the presence of transglutaminase. Among the microbial cultures screened <em>Streptomyces</em> sp. D1, showed maximum transglutaminase activity. In this study characterization of transglutaminase and its application to modifying the properties of panner (Indian cottage cheese) in the form of cross linking was investigated. Optimum temperature and pH for enzyme was found to be at 50°C and 6.0, respectively. Optimization of media ingredients for maximizing the transglutaminase activity using <em>Streptomyces</em> sp. D1 was carried out using central composite design. Response surface methodology was employed to standardize the optimum media composition for maximum enzyme activity. Three factors such as carbon source, nitrogen source and pH were tested for the maximum enzyme activity as response. The optimized medium with sugarcane molasses as carbon source 6.0% (w/v), peptone as nitrogen source 1.75% (w/v) were found to be optimal at initial pH 6.5 and incubation temperature 30.0°C with agitation at 100 rpm for 96h. The enzyme activity of transglutaminase obtained from the optimized medium was found to be 4.1 (AU/ml). Low cost substrate such as sugarcane molasses in the form of a renewable substrate is proposed to be suitable even for scale-up production of enzyme and for industrial applications. The ethanol fractionated transglutaminse treated milk was found to produce more paneer with increased moisture content while reduction in cooking loss of the paneer prepared using enzyme treated milk is also reported.</p>

Aldose reductase regulates acrolein-induced cytotoxicity in human small airway epithelial cells

Aldose reductase (AR), a glucose-metabolizing enzyme, reduces lipid aldehydes and their glutathione conjugates with more than 1000-fold efficiency (Km aldehydes 5-30 µM) relative to glucose. Acrolein, a major endogenous lipid peroxidation product as well as a component of environmental pollutants and cigarette smoke, is known to be involved in various pathologies including atherosclerosis, airway inflammation, COPD, and age-related disorders, but the mechanism of acrolein-induced cytotoxicity is not clearly understood. We have investigated the role of AR in acrolein-induced cytotoxicity in primary human small airway epithelial cells (SAECs). Exposure of SAECs to varying concentrations of acrolein caused cell death in a concentration- and time-dependent manner. AR inhibition by fidarestat prevented the low-dose (5-10 µM) but not the high-dose (>10 µM) acrolein-induced SAEC death. AR inhibition protected SAECs from low-dose (5 µM) acrolein-induced cellular reactive oxygen species (ROS). Inhibition of acrolein-induced apoptosis by fidarestat was confirmed by decreased condensation of nuclear chromatin, DNA fragmentation, comet tail moment, and annexin V fluorescence. Further, fidarestat inhibited acrolein-induced translocation of the proapoptotic proteins Bax and Bad from the cytosol to the mitochondria and that of Bcl2 and BclXL from the mitochondria to the cytosol. Acrolein-induced cytochrome c release from mitochondria was also prevented by AR inhibition. The mitogen-activated protein kinases (MAPKs), such as extracellular signal-regulated kinases 1 and 2, stress-activated protein kinase/c-Jun NH2-terminal kinase, and p38MAPK, and c-Jun were transiently activated in airway epithelial cells by acrolein in a concentration- and time-dependent fashion, which was significantly prevented by AR inhibition. These results suggest that AR inhibitors could prevent acrolein-induced cytotoxicity in the lung epithelial cells.

Modified Hodge test: A useful and the low-cost phenotypic method for detection of carbapenemase producers in Enterobacteriaceae members

Background:

The global spread of antimicrobial resistance has acquired greater significance in the public health perspective. Drug resistance has posed a threat for the management of various hospital-acquired infections (HAI). For bacteria producing extended spectrum ß lactamase, carbapenems are the drug of choice. However, treatment failures are still a cause of concern due to carbapenemase producers.

Aim:

Various phenotypic and genotypic methods are available for the detection of carbapenemase producers. Studies thus far have mostly concentrated on comparing various methods for detection of carbapenemase producers. We used low-cost and the easily performed modified Hodge test (MHT) for detecting the carbapenemase producers in Enterobacteriaceae members isolated from various clinical specimens.

Material and Methods:

The study included 1072 clinical isolates of Enterobacteriaceae collected in India between April 2008 and February 2010. MHT was performed on all the isolates in accordance with CDC and CLSI guidelines.

Results:

The carbapenemase activity was detected in 35.9% (385/1072) of the isolates. Klebsiella spp. 28.7% (80/278), Citrobacter spp. 20.4% (25/122), 11.3% (38/334) in E. coli, 20.3% (45/221) in Enterobacter spp., and 16.2% (9/117) in Proteus spp. revealed variable resistance activities against carbapenems.

Conclusion:

Enterobacteriaceae members are among the most common and easily transferable bacterial species responsible for severe HAI. This study revealed a high percentage of Enterobacteriaceae clinical isolates producing carbapenemases in India. Detection of such bacteria, formulating hospital antibiogram, and monitoring the usage of antimicrobial drugs is recommended.

A Study of Alternate Biomarkers in HIV Disease and Evaluating their Efficacy in Predicting T CD4+ Cell Counts and Disease Progression in Resource Poor Settings in Highly Active Antiretroviral Therapy (HAART) Era

INTRODUCTION

Human Immunodeficiency Virus (HIV), the causative agent of AIDS, has been a challenge to medical fraternity since it was first discovered in 1983. About 40 million people are living with HIV infection globally and 99% of the infected people are in south East Asia (SEA). Traditionally, HIV disease and progression, initiation of HAART and response to therapy is monitored by assessing in regular intervals, the T CD4+ cell counts and plasma HIV/RNA viral load. Resource poor, low and low - middle income group countries still have no finances to acquire infrastructure and scientific technology for performing such tests.

OBJECTIVES

Since very few studies are available, they have demonstrated the role of alternate biomarkers that can be used to predict CD4 cell counts and thereby, monitor HIV disease progression and HAART. We aimed to measure certain haematological parameters in HIV seropositive patients and to evaluate their efficacy in predicting TCD4+ cell counts.

METHODS

The study group included 250 HIV seropositive patients with an age range of 18-65 years. 140(56%) males and 110(44%) females were included in the study. Absolute TCD4+cell counts and CD8+T cell counts were measured by using a flow cytometer. (MMWR Recommendations and Reports, 1992) TLC; HB%, AEC and ESR were estimated by using conventional haematological methods. CRP was evaluated by latex agglutination test (Immuno CRP Latex Agglutination Test).

RESULTS

Among the tested haematological markers, a TLC of <1800 cells/mm(3) showed high specificity (100%) in predicting CD4 counts of < 200 cells/mm(3), with an accuracy of 61.46%. Haemoglobin and Absolute Eosinophilic counts showed high specificities of 84.09% and 94.32% respectively in predicting CD4 counts which were below 350 cells/mm(3). ESR with 98.98% sensitivity and AEC which had 83.67% sensitivity were able to predict CD4 counts of <200 cells/mm(3).

CONCLUSION

Among the tested biomarkers, it was seen that Absolute Eosinophilic counts of more than 550 cells/mm(3), Blood Haemoglobin which was less than 10 g%, ESR which measured more than 20 mm, CRP values of >1.2 and TLC of <1800 cells/mm(3) could be helpful in predicting CD4 cell counts of < 350 and <200 cells/mm(3).

Prevention of VEGF-induced growth and tube formation in human retinal endothelial cells by aldose reductase inhibition

OBJECTIVE

Since diabetes-induced vascular endothelial growth factor (VEGF) is implicated in retinal angiogenesis, we aimed to examine the role of aldose reductase (AR) in VEGF-induced human retinal endothelial cells (HREC) growth and tube formation.

MATERIALS AND METHODS

HRECs were stimulated with VEGF and cell-growth was determined by MTT assay. AR inhibitor, fidarestat, to block the enzyme activity and AR siRNA to ablate AR gene expression in HREC were used to investigate the role of AR in neovascularization using cell-migration and tube formation assays. Various signaling intermediates and angiogenesis markers were assessed by Western blot analysis. Immuno-histochemical analysis of diabetic rat eyes was performed to examine VEGF expression in the retinal layer.

RESULTS

Stimulation of primary HREC with VEGF caused increased cell growth and migration, and AR inhibition with fidarestat or ablation with siRNA significantly prevented it. VEGF-induced tube formation in HREC was also significantly prevented by fidarestat. Treatment of HREC with VEGF also increased the expression of VCAM, AR, and phosphorylation and activation of Akt and p38-MAP kinase, which were prevented by fidarestat. VEGF-induced expression of VEGFRII in HREC was also prevented by AR inhibition or ablation.

CONCLUSIONS

Our results indicate that inhibition of AR in HREC prevents tube formation by inhibiting the VEGF-induced activation of the Akt and p38-MAPK pathway and suggest a mediatory role of AR in ocular neovascularization generally implicated in retinopathy and AMD.

Current prospective of aldose reductase inhibition in the therapy of allergic airway inflammation in asthma

The prevalence of asthma and costs of its care have been continuously increasing, but novel therapeutic options to treat this inflammatory disease have not been brought to the US market. Current therapies such as inhaled steroids, long-acting beta-agonist bronchodilators, antihistamines and immunomodulators may control the symptoms of allergic asthma but fail to modify the underlying disease. Excessive use of steroids and other immunosuppresents alter the patient's quality of life, produce undesirable toxicities, and increase the risk of other pathologies such as diabetes. Hence novel therapeutic options to manage asthma are desirable. In the present review, we have discussed the role of the polyol pathway enzyme aldose reductase (AR) in the amplification of allergic airway inflammation. Recent studies have indicated that AR inhibition prevents the NF-κB-dependent generation of pro-inflammatory cytokines and chemokines in mouse models of allergic airway inflammation indicating the potential use of AR inhibition as a novel tool to control allergic responses. Since orally available AR inhibitors have already undergone phase III clinical trials for diabetic neuropathy and appear to have a manageable side effects profile, they could be readily developed as potential new drugs for the treatment of asthma and related complications.

Bacterial cellulose nanocrystals exhibiting high thermal stability and their polymer nanocomposites

Nanocrystals prepared from bacterial cellulose are considered as 'green nanomaterials' depending on their renewable nature and ease of production without the involvement of hazardous chemical treatments. In this investigation, a top down approach was followed for the preparation of bacterial cellulose nanocrystals (BCNC) using a commercially available cellulase enzyme so as to retain native properties of bacterial cellulose even in its nanodimensional form. The morphological and dimensional parameters of BCNC were studied using atomic force microscope (AFM) and transmission electron microscope (TEM). Thermal properties of BCNC produced using the novel enzyme treatment and conventional sulfuric acid hydrolysis were compared. The thermal stability of enzyme processed BCNC was almost two fold higher than sulfuric acid processed ones. Further, the activation energy required for decomposition of enzyme processed BCNC was much higher than the other. Using this enzyme processed BCNC, Polyvinylalcohol (PVA) nanocomposite films were prepared and characterized. Incorporation of these nanocrystals in polymer matrix resulted in a remarkable improvement in the thermal stability as well as mechanical properties of nanocomposite films. These nanocomposites exhibited higher melting temperature (Tm) and enthalpy of melting (ΔHm) than those of pure PVA, suggesting that the addition of nanocrystals modified the thermal properties of PVA. The effective load transfer from polymer chains to the BCNC resulted in an improved tensile strength from 62.5 MPa to 128 MPa, by the addition of just 4 wt% of BCNC. Furthermore, the elastic modulus was found to increase from 2 GPa to 3.4 GPa. The BCNC obtained through cellulose treatment under controlled conditions were associated with several desirable properties and appear to be superior over the conventional methods of nanocrystals production. The enzymatic method followed in this study is expected to contribute the fabrication of high performance polymer nanocomposites in a much greener and innovative manner.

Understanding the role of aldose reductase in ocular inflammation

Aldose reductase, although identified initially as a glucose-reducing enzyme via polyol pathway, is believed to be an important component of antioxidant defense system as well as a key mediator of oxidative stress-induced molecular signaling. The dual role played by AR has made it a very important enzyme for the regulation of not only the cellular redox state by detoxifying the reactive lipid-aldehydes generated by lipid peroxidation which is crucial in the cellular homeostasis, but also in the regulation of molecular signaling cascade that may regulate oxidative stress-induced cytotoxic events. Search for the new molecular targets to restrain the oxidative stress-induced inflammation has resulted in the identification of AR as an unanticipated mediator of oxidative stress-induced signaling. Although, in last one decade or so AR has been implicated in various inflammation-related diseases conditions ranging from diabetes, sepsis, cancer, cardiovascular and ocular inflammation, however, a critical evaluation of the clinical efficacy of AR inhibitors awaits a better understanding of the role of AR in regulating inflammation, especially in ocular inflammation.

Simplification and optimization of deMan Rogosa Sharpe (MRS) medium for enhanced production of bacteriocin by Weissella paramesenteroides DFR-8

Complex growth medium such as deMan Rogosa Sharpe (MRS) medium, commonly used for cultivation of fastidious lactic acid bacteria (LAB) interfere in bacteriocin purification. Sometimes all the ingredients of a defined medium are not required by all LAB strains for bacteriocin production. In the present study, composition of the MRS medium for the production of bacteriocin by Weissella paramesenteroides DFR-8, an isolate from cucumber (Cucumis sativus), was simplified and optimized with a step-wise strategy. In the first step, production profile, effect of incubation temperature, various C and N sources were investigated. In the second step, central composite rotatable design was employed to decide the optimal concentration of 3 key components (glucose, tryptone and pH) and the experimental results were fitted with a second order polynomial regression equation. According to the set criteria, the predicted bacteriocin titer from a medium containing 7.99% glucose, 9% tryptone, pH 7.5 (91.9% desirability) was 540 AU/ml and the observed bacteriocin titer was 538 AU/ml that indicated the validity of the developed model. Using optimized medium, bacteriocin titer of 674.5 AU/ml could be achieved after 72 h of fermentation that is nearly 2.5 fold higher than that obtained from unmodified MRS medium.

Tropical soil microflora of spice-based cropping systems as potential antagonists of root-knot nematodes

Suppression of plant parasitic nematodes with nematode predators, parasites or antagonists is an eco-friendly approach than the toxic chemicals. In a study, soil borne fungi from the rhizosphere of major spice crops were collected from diverse cropping systems prevailing in three southern states of India. A series of in vitro studies were conducted using 73 freshly collected fungal isolates and 76 isolates obtained from other sources. Out of this 67 isolates were not parasitic on females of root-knot nematodes whereas 115 isolates, though colonized the egg masses, did not show any signs of parasitism on nematode eggs. Fifty-nine isolates showed 50-90% inhibition in egg hatch. Pochonia chlamydospora, Verticillium lecanii, Paecilomyces lilacinus, and few isolates of Trichoderma spp. showed >25% parasitism on root-knot nematode eggs. The most promising isolates in this study were one isolate each of Aspergillus (F.45), Fusarium (F.47), and Penicillium (F.59); three each isolates of Trichoderma (F.3, F.52, and F.60) and Pochonia (F.30 and Vc.3) Verticillium (Vl); and two isolates of fungi that could not be identified (F.28 and F.62). Parasitism by Aspergillus tamarii, Aspergillus ustus, Drechslera sp., Humicola sp., and Scopulariopsis sp. on root-knot nematode eggs or females, reported in the present study, are new reports.

Structural and kinetic modifications of aldose reductase by S-nitrosothiols

Modification of aldose reductase (AR) by the nitrosothiols S-nitroso-N-acetyl penicillamine (SNAP) and N-(beta-glucopyranosyl)-N(2)-acetyl-S-nitrosopenicillamide (glyco-SNAP) resulted in a 3-7-fold increase in its k(cat) and a 25-40-fold increase in its K(m) for glyceraldehyde. In comparison with the native protein, the modified enzyme was less sensitive to inhibition by sorbinil and was not activated by SO(2-)(4) anions. The active-site residue, Cys-298, was identified as the main site of modification, because the site-directed mutant in which Cys-298 was replaced by serine was insensitive to glyco-SNAP. The extent of modification was not affected by P(i) or O(2), indicating that it was not due to spontaneous release of nitric oxide (NO) by the nitrosothiols. Electrospray ionization MS revealed that the modification reaction proceeds via the formation of an N-hydroxysulphenamide-like adduct between glyco-SNAP and AR. In time, the adduct dissociates into either nitrosated AR (AR-NO) or a mixed disulphide between AR and glyco-N-acetylpenicillamine (AR-S-S-X). Removal of the mixed-disulphide form of the protein by lectin-column chromatography enriched the preparation in the high-K(m)-high-k(cat) form of the enzyme, suggesting that the kinetic changes are due to the formation of AR-NO, and that the AR-S-S-X form of the enzyme is catalytically inactive. Modification of AR by the non-thiol NO donor diethylamine NONOate (DEANO) increased enzyme activity and resulted in the formation of AR-NO. However, no adducts between AR and DEANO were formed. These results show that nitrosothiols cause multiple structural and functional changes in AR. Our observations also suggest the general possibility that transnitrosation reactions can generate both nitrosated and thiolated products, leading to non-unique changes in protein structure and function.

Chemoenzymatic synthesis of pyrrolo[2,1-b]quinazolinones: lipase-catalyzed resolution of vasicinone

A facile synthesis of bronchodilatory pyrrolo[2,1-b]quinazoline alkaloids by azidoreductive cyclization strategy employing TMSCl-NaI and bakers' yeast is described. Both the chemical and enzymatic methods are mild and take place at room temperature in good yields. Further, synthesis and resolution of vasicinone has been carried out by employing different lipases. It has been observed that lipase PS provides acetate of (S)-vasicinone in 98% ee.

Metabolic regulation of aldose reductase activity by nitric oxide donors

Regulation of aldose reductase (AR), a member of the aldo-keto reductase superfamily, by nitric oxide (NO) donors was examined. Incubation of human recombinant AR with S-nitrosoglutathione (GSNO) led to inactivation of the enzyme and the formation of an AR-glutathione adduct. In contrast, incubation with S-nitroso-N-acetyl penicillamine (SNAP) or N-(beta-D-glucopyranosyl)-SNAP (GlycoSNAP) led to an increase in enzyme activity which was accompanied by the direct nitrosation of the enzyme and the formation of a mixed disulfide with the NO-donor. To examine in vivo modification, red blood cells (RBC) and rat aortic vascular smooth muscle cells (VSMC) were incubated with 1 mM GSNO or SNAP. Exposure of VSMC to SNAP and GSNO for 2 h at 37 degrees C led to approximately 71% decrease in the enzyme activity with DL-glyceraldehyde as the substrate. Similarly, exposure of RBC in 5 mM glucose to NO-donors for 30 min at room temperature, followed by increasing the glucose concentration to 40 mM, resulted in >75% decrease in the formation of sorbitol. These investigations indicate that NO and/or its bioactive metabolites can regulate cellular AR, leading to either activation (by nitrosation) or inactivation (by S-thiolation).

Characterization of the glutathione binding site of aldose reductase

Despite extensive investigations, the physiological role of the polyol pathway enzyme-aldose reductase (AR) remains obscure. While the enzyme reduces glucose in vivo and in vitro, kinetic and structural studies indicate inefficient carbohydrate binding to the active site of the enzyme. The active site is lined by hydrophobic residues and appears more compatible with the binding of medium- to long-chain aliphatic aldehydes or hydrophobic aromatic aldehydes. In addition, our recent studies show that glutathione (GS) conjugates are also reduced efficiently by the enzyme. For instance, the GS conjugate of acrolein is reduced with a catalytic efficiency 1000-fold higher than the parent aldehyde, indicating specific recognition of glutathione by the active site residues of AR. An increase in the catalytic efficiency upon glutathiolation was also observed with trans-2-nonenal, trans-2-hexenal and trans, trans-2,4-decadienal, establishing that enhancement of catalytic efficiency was specifically due to the glutathione backbone and not specific to the aldehyde. Structure-activity relationships with substitution or deletion of amino acids of GSH indicated specific interactions of the active site with gamma-Glu1 and Cys of GSH. Molecular modeling revealed that the glutathione-propanal conjugate could bind in two distinct orientations. In orientation 1, gamma-Glu1 of the conjugate interacts with Trp20, Lys21 and Val47, and Gly3 interacts with Ser302 and Leu301, whereas in orientation 2, the molecule is inverted with gamma-Glu1 interacting with Ser302, and Leu301. Taken together, these data suggest that glutathiolation of aldehydes enhances their compatibility with the AR active site, which may be of physiological significance in detoxification of endogenous and xenobiotic aldehydes.

Selective recognition of glutathiolated aldehydes by aldose reductase

In this study, the selectivity and specificity of aldose reductase (AR) for glutathionyl aldehydes was examined. Relative to free aldehydes, AR was a more efficient catalyst for the reduction of glutathiolated aldehydes. Reduction of glutathionyl propanal [gammaGlu-Cys(propanal)-Gly] was more efficient than that of Gly-Cys(propanal)-Gly and gamma-aminobutyric acid-Cys(propanal)-Gly suggesting a possible interaction between alpha-carboxyl of the conjugate and AR. Two active site residues, Trp20 or Ser302, were identified by molecular modeling as potential sites of this interaction. Mutations containing tryptophan-to-phenylalanine (W20F) and serine-to-alanine (S302A) substitutions did not significantly affect reduction of free aldehydes but decreased the catalytic efficiency of AR for glutathiolated aldehydes. Combined mutations indicate that both Trp20 and Ser302 are required for efficient catalysis of the conjugates. The decrease in efficiency due to W20F mutation with glutathionyl propanal was not observed with gamma-aminobutyric-Cys(propanal)-Gly or Gly-Cys-(propanal)-Gly, indicating that Trp20 is involved in binding the alpha-carboxyl of the conjugate. The effect of the S302A mutation was less severe when gammaGlu-Cys(propanal)-Glu rather than glutathionyl propanal was used as the substrate, consistent with an interaction between Ser302 and Gly-3 of the conjugate. These observations suggest that glutathiolation facilitates aldehyde reduction by AR and enhances the range of aldehydes available to the enzyme. Because the N-terminal carboxylate is unique to glutathione, binding of the conjugate with the alpha-carboxyl facing the bottom of the alpha/beta-barrel may assist in the exclusion of unrelated peptides and proteins.

Kinetic and structural characterization of the glutathione-binding site of aldose reductase

Aldose reductase (AR), a member of the aldo-keto reductase superfamily, has been implicated in the etiology of secondary diabetic complications. However, the physiological functions of AR under euglycemic conditions remain unclear. We have recently demonstrated that, in intact heart, AR catalyzes the reduction of the glutathione conjugate of the lipid peroxidation product 4-hydroxy-trans-2-nonenal (Srivastava, S., Chandra, A., Wang, L., Seifert, W. E., Jr., DaGue, B. B., Ansari, N. H., Srivastava, S. K., and Bhatnagar, A. (1998) J. Biol. Chem. 273, 10893-10900), consistent with a possible role of AR in the metabolism of glutathione conjugates of aldehydes. Herein, we present several lines of evidence suggesting that the active site of AR forms a specific glutathione-binding domain. The catalytic efficiency of AR in the reduction of the glutathione conjugates of acrolein, trans-2-hexenal, trans-2-nonenal, and trans,trans-2,4-decadienal was 4-1000-fold higher than for the corresponding free alkanal. Alterations in the structure of glutathione diminished the catalytic efficiency in the reduction of the acrolein adduct, consistent with the presence of specific interactions between the amino acid residues of glutathione and the AR active site. In addition, non-aldehydic conjugates of glutathione or glutathione analogs displayed active-site inhibition. Molecular dynamics calculations suggest that the conjugate adopts a specific low energy configuration at the active site, indicating selective binding. These observations support an important role of AR in the metabolism of glutathione conjugates of endogenous and xenobiotic aldehydes and demonstrate, for the first time, efficient binding of glutathione conjugates to an aldo-keto reductase.

Purification and characterization of the hepatic CYP2C and 3A isozymes from phenobarbitone pretreated rhesus monkey

Hepatic P450s, named M-3 and M-4 were purified from phenobarbitone pretreated rhesus monkey. These demonstrated polypeptide molecular mass of 50 and 52.5 kDa and specific content of 12 and 20 nmol P450/mg protein, respectively. Both the isozymes demonstrated low spin state of heme. Antibodies raised against M-3 inhibited the activity of aminopyrine, erythromycin and ethylmorphine N-demethylase in the microsomes obtained from PB pretreated rhesus monkey by 76, 40 and 35%, respectively. M-4 did the same by 69, 85 and 79%, respectively. These observations indicated M-3 and M-4 to be the members of CYP2C and 3A subfamilies, respectively. These results were substantiated by the observations that M-3 metabolized aminopyrine whereas M-4 metabolized aminopyrine, erythromycin and ethylmorphine in the reconstituted system. Microsomal lipids and cytochrome b5 enhanced the rate of these reactions. Further confirmation to the identity of these isozymes was provided by N-terminal amino acid sequences. The first 10 N-terminal amino acid residues of M-3 were 90% similar to CYP2C20 and 2C9 and that of M-4 were 100 and 90% similar to CYP3A8 and 3A5, respectively. In conclusion, two isozymes of hepatic P450 purified from PB pretreated rhesus monkey belong to CYP2C and 3A subfamilies.

Purification of catalytically active hepatic NADPH cytochrome P450 oxidoreductase from the rhesus monkey, Macaca mulatta

Hepatic NADPH cytochrome P450 oxidoreductase capable of supporting polysubstrate monooxygenase (PSMO) reactions was purified from microsomes obtained from phenobarbitone (PB) pretreated rhesus monkey. Two preparations of the enzyme purified by affinity and molecular exclusion chromatographic techniques demonstrated specific content of 19.5 and 37.9 nmol cytochrome c reduced/min/mg protein and subunit molecular weight of 66 and 80 kDa, respectively. Both forms supported oxidation of NADPH and reduction of cytochrome c and DCIP but only 80 kDa preparation supported PSMO reactions. The reconstituted system consisted of hepatic P450, NADPH cytochrome P450 oxidoreductase, cytochrome b5 all purified from PB pretreated rhesus monkey and dilauroyl phosphatidylcholine or microsomal lipid. Eighty kDa preparation supported the metabolism of aminopyrine and tolbutamide by hepatic P4502C and erythromycin, ethylmorphine and nifedipine by hepatic P450 3A, respectively. The turnover of these substrates increased in the presence of partially purified cytochrome b5 from the rhesus monkey. To best of our knowledge this is the first report on the purification of monkey hepatic NADPH cytochrome P450 oxidoreductase capable of supporting in vitro PSMO by different isozymes of P450.

Gene regulation of cytochrome P450--an overview

Xenobiotics have played a role in elucidating the regulation of gene expression of hepatic cytochrome P450 in the eukaryotes. The major regulation of P450 genes in the eukaryotes is at the transcriptional and post transcriptional level. Polycyclic aromatic hydrocarbons regulate the gene expression by binding the cytosolic aryl hydrocarbon receptor and its translocation to the nucleus where it forms a ternary complex with aryl hydrocarbon nuclear translocator. The ternary complex PAH-AHR-ARNT acts as a transcription factor and binds aromatic hydrocarbon responsive element to increase the expression of CYP1A1 gene. Phenobarbitone and ethanol regulate the expression of respective P450s within CYP2 gene family by different mechanisms but without the involvement of a cytosolic receptor. PB uses phosphorylation as a switch to increase the affinity of the transcription factor(s) for the positive rather than negative PB regulatory element within CYP2B1/2. This is one of the novel ways that nature has designed for a protein to act as a negative as well as a positive acting transcription factor. Ethanol regulates the expression of CYP2E1 by posttranslational stabilization making it resistant to the proteolytic digestion. Steroids regulate expression of CYP3A genes through a receptor mediated mechanism. The binary complex of the steroid and its receptor increases the transcription of CYP3 genes by binding glucocorticoid responsive element which is already occupied by another protein. Peroxisome proliferators also follow a receptor mediated mechanism in which a binary complex of PP activated receptor and retinoid X receptor acts a transcription factor and increases the expression of CYP4A genes by binding peroxisome proliferator responsive element. These studies demonstrate that PAH, glucocorticoids and PP follow a receptor mediated whereas PB and ethanol follow a nonreceptor mediated mechanism for the regulation of respective P450 genes in the eukaryotes.

Induction of hepatic cytochrome P450 by phenobarbitone in rhesus monkey (Macaca mulatta)

An intraperitoneal administration of PB at a daily dose of 50 mg Kg-1 body wt for 4 days increased the specific content of hepatic microsomal heme, cytochrome P450 and the activity of aminopyrine N-demethylase by 1.8, 2.8 and 3.5 fold respectively. These results were substantiated by the intensification of the 52.5 KDa polypeptide in the electrophoretogram of sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the hepatic microsomes obtained from PB-pretreated versus control macaques. PB did not affect the hepatic content of cytochrome b5 and the activity of NADPH cytochrome c reductase, whereas it decreased the activity of NADH cytochrome c reductase in the rhesus monkeys. To the best of our knowledge this is a first report on the induction of hepatic cytochrome P450 and related enzymes by PB in rhesus monkeys.

Citrus fruits--varieties, chemistry, technology, and quality evaluation. Part II. Chemistry, technology, and quality evaluation. A. Chemistry

In Part 2 of this review on citrus fruits, the literature on chemistry, technology, and quality evaluation are critically considered. Sweet oranges, mandarin, grapefruit, lemon, and lime are generally used for processing. The literature on chemical components of citrus fruit which include sugars, polysaccharides, oraganic acids, nitrogenous constituents and lipids; carotenoids which contribute to color; vitamins and minerals, and flavonoids; limonoids, some of which impart bitterness to the juice; and the volatile components which contribute to aroma have been reviewed. Chilled and pasteurized juices, juice concentrates, and beverages are the important products manufactured commercially, and to a limited extent powdered citrus juices, canned segments, and marmalades. The literature on the manufacture of these products also as new types of juice and oil extractors; TASTE and other types of evaporators; tank farms to store juice and concentrate in bulk; aseptic filling in bulk containers and retail packs; alternate flexible and rigid containers other than glass and tin; and recovery of volatile flavoring constituents during juice processing are some of the important technological developments in the recent past and have been discussed. Bitterness in citrus juices and its control, composition of cloud, and its stability and changes during storage have been reviewed. Essential oils, pectin, frozen and dried juice sacs, dried pulp and molasses, flavonoids, seed oil, and meal are the important byproducts, the manufacture of which is given in essential details. Generally, consumers judge the product on the basis of its sensory attributes. The quality of finished product is dependent upon the raw materials used and control of processes. The U.S. Department of Agriculture (USDA) standards for different products, physicochemical and microbiological parameters prescribed as indices of quality of fruit, juice, concentrate, and other products; composition of essential oils; and aroma concentrates are discussed in relation to sensory quality. Analytical methods for compounds affecting quality, and methods for detection of adulteration in different citrus products are briefly reviewed. The importance of sensorily evaluating quality of citrus products to select and develop quality control indices is emphasized. Areas where further research are required are indicated. A comprehensive bibliography is provided to aid further study and research.

Citrus fruits. Part II. Chemistry, technology, and quality evaluation. B. Technology

In Part II of this review on citrus fruits, the literature on chemistry, technology, and quality evaluation are critically considered. Sweet oranges, mandarin, grapefruit, lemon, and lime are generally used for processing. The literature on chemical components of citrus fruit which include sugars, polysaccharides, organic acids, nitrogenous constituents and lipids; carotenoids which contribute to color; vitamins and minerals and flavonoids; limonoids, some of which impart bitterness to the juice; and the volatile components which contribute to aroma were reviewed in section A. Chilled and pasteurized juices, juice concentrates, and beverages are the important products manufactured commercially, and to a limited extent powdered citrus juices, canned segments, and marmalades. The literature on the manufacture of these products also as new types of juice and oil extractors; TASTE and other types of evaporators; tank farms to store juice and concentrate in bulk; aseptic filling in bulk containers and retail packs; alternate flexible and rigid containers other than glass and tin; and recovery of volatile flavoring constituents during juice processing are some of the important technological developments in the recent past and have been discussed in this section. Bitterness in citrus juices and its control, composition of cloud, and its stability and changes during storage have been reviewed. Essential oils, pectin, frozen and dried juice sacs, dried pulp and molasses, flavonoids, seed oil, and meal are the important byproducts, the manufacture of which is given in essential details. Generally, consumers judge the product on the basis of its sensory attributes. The quality of finished product is dependent upon the raw materials used and control of processes. In section C, the U.S. Department of Agriculture (USDA) standards for different products, physicochemical and microbiological parameters prescribed as indices of quality of fruit, juice, concentrate, and other products; composition of essential oils; and aroma concentrates are discussed in relation to sensory quality. Analytical methods for compounds affecting quality, and methods for detection of adulteration in different citrus products are briefly reviewed. The importance of sensorily evaluating quality of citrus products to select and develop quality control indices is emphasized. Areas where further research are required are indicated. A comprehensive bibliography is provided to aid further study and research.