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Enzyme Content (enzyme + content)
Selected AbstractsEffect of aroclor 1248 and two pure PCB congeners on phospholipase D activity in rat renal tubular cell culturesJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 2 2007Mercedes Fernández Santiago Abstract This paper elucidates the effect of different polychlorinated biphenyls (PCBs) on the phospholipase D (PLD) activity in soluble and particulate fractions of rat renal proximal tubular culture cells. Treatment with Aroclor 1248 (a commercial PCB mixture) caused a marked increase in the activity of PLD in intact renal tubular cells. The PLD activity was increased by Aroclor 1248 in the particulate fraction while the enzyme activity was unaffected in the soluble fraction. This work also shows that PCB 153 (2,2',4,4',5,5'-hexachlorobiphenyl, a di-ortho-substituted nonplanar congener) can increase the activity of PLD only in the particulate fraction. The exposure of cell cultures to PCB 77 (3,3',4,4'-tetrachlorobiphenyl, a non-ortho-substituted planar congener) does not alter PLD activity. These results suggest that PCB effects are structure dependent. Therefore, in order to clarify the molecular mechanism of activation of PLD by PCBs, the contents of immunoreactive PLD were examined by immunoblot analysis. Renal tubular cells expressed a PLD protein of 120 kDa corresponding with the PLD1 mammalian isoform in both the particulate and the soluble fraction. Aroclor 1248, PCB 153, and PCB 77 do not induce changes in the levels of PLD protein. These data indicate that PCBs, particularly nonplanar congeners, increase PLD activity. Moreover, these changes could not be demonstrated in the enzyme content in rat renal tubular cell cultures. © 2007 Wiley Periodicals, Inc. J Biochem Mol Toxicol 21:68,75, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20160 [source] Lipase-catalyzed ethanolysis of soybean oil in a solvent-free system using central composite design and response surface methodologyJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2008Rafael Costa Rodrigues Abstract BACKGROUND: In this work we describe the synthesis of ethyl esters, commonly known as biodiesel, using refined soybean oil and ethanol in a solvent-free system catalyzed by lipase from Thermomyces lanuginosus. Central composite design and response surface methodology (RSM) were employed to optimize the biodiesel synthesis parameters, which were: reaction time, temperature, substrate molar ratio, enzyme content, and added water, measured as percentage of yield conversion. RESULTS: The optimal conditions obtained were: temperature, 31.5 °C; reaction time, 7 h; substrate molar ratio, 7.5:1 ethanol:soybean oil; enzyme content, 15% (g enzyme g,1 oil); added water, 4% (g water g,1 oil). The experimental yield conversion obtained under these conditions was 96%, which is very close to the maximum predicted value of 94.4%. The reaction time-course at the optimal values indicated that 5 h was necessary to obtain high yield conversions. CONCLUSION: A high yield conversion was obtained under the optimized conditions, with relative low enzyme content and short time. Comparison of predicted and experimental values showed good correspondence, implying that the empirical model derived from RSM can be used to adequately describe the relationship between the reaction parameters and the response (yield conversion) in lipase-catalyzed biodiesel synthesis. Copyright © 2008 Society of Chemical Industry [source] Profile of P-glycoprotein distribution in the rat and its possible influence on the salbutamol intestinal absorption processJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2004Belén Valenzuela Abstract The intrinsic absorption of salbutamol in different intestinal segments of the rat was measured and related with the corresponding intestinal P-glycoprotein (P-gp) expression levels. The apparent absorption rate constants (ka, h,1) observed in each fraction by means of the "in situ" rat gut absorption method after perfusion of a 0.29-mM isotonic solution of salbutamol were used as absorption indexes. In a separate series of studies, a semiquantitative analysis of the mRNA expression of P-gp by means of polymerase chain reaction and Western blot with an antibody raised against the P-gp were also performed. The "in situ" ka values determined in the different segments (h,1) showed that the absorption is not homogeneous along the intestinal tract, that is, 0.499,±,0.054 for colon, 0.474,±,0.052 for the proximal segment, 0.345,±,0.014 for the mean, and 0.330,±,0.023 for the distal fraction. Addition of verapamil to the perfusion fluid did provide a better absorption of salbutamol in the distal segment. The analysis of the mRNA expression and levels of P-gp showed that the enzyme content in each section of the intestine was inversely related to salbutamol absorption. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:1641,1648, 2004 [source] Trypsin enzyme activity during larval development of Litopenaeus vannamei (Boone) fed on live feedsAQUACULTURE RESEARCH, Issue 5 2002A C Puello-Cruz Abstract Larval stages of the Pacific white shrimp, Litopenaeus vannamei (Boone) were fed standard live diets of mixed microalgae from the first to the third protozoea (PZ1 to PZ3), followed by Artemia nauplii until post-larvae 1 (PL1). Trypsin enzyme activity for each larval stage was determined using N -,-p-toluenesulphonyl- l -arginine methyl ester (TAME) as a substrate. Results were expressed as enzyme content to assess ontogenetic changes during larval development. Tissue trypsin content (IU µg,1 DW for each larval stage) was significantly highest at the PZ1 stage and declined through subsequent stages to PL1. This contrasts with previously observed patterns of trypsin development in Litopenaeus setiferus (Linnaeus) and other penaeid genera, which exhibit a peak in trypsin activity at the third protozoea/first mysis (PZ3/M1) larval stage. Litopenaeus vannamei larvae transferred to a diet of Artemia at the beginning of the second protozoea (PZ2) stage were significantly heavier on reaching the first mysis stage (M1) than those fed algae, while survival was not significantly different between treatments. At both PZ2 and PZ3 stages, trypsin content in larvae feeding on Artemia was significantly lower than in those feeding on algae. The rapid decline in trypsin content from PZ1 and the flexible enzyme response from PZ2 suggest that L. vannamei is physiologically adapted to transfer to a more carnivorous diet during the mid-protozoeal stages. [source] Ontogeny of human hepatic cytochromes P450JOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 4 2007Ronald N. Hines Abstract Significant changes in drug-metabolizing enzyme (DME) expression occur during ontogeny. Such changes can have a profound effect on therapeutic efficacy in the fetus and child, as well as the risk for adverse drug reactions. To gain a better understanding of DME ontogeny, enzyme contents for six key cytochromes P450 were measured in 240 human liver samples representing ages from 8 weeks gestation to 18 years. Where possible, both quantitative western blotting and activity assays with probe substrates were performed. Although oversimplified, the DME can be grouped into one of three categories. As typified by CYP3A7, some enzymes are expressed at their highest level during the first trimester and either remain at high concentrations or decrease during gestation and are silenced or expressed at low levels within 1,2 years after birth. These data cause one to query whether these enzymes have an important endogenous function. Representatives of a second group, CYP3A5 and CYP2C19, are expressed at relatively constant levels throughout gestation. Postnatal increases in CYP2C19 are observed within the first year, but not for CYP3A5. CYP2C9, 2E1, and 3A4 are more typical of a third group of enzymes that are not expressed or are expressed at low levels in the fetus with the onset of expression generally in either the second or third trimester. Substantial increases in expression are observed within the first 1,2 years after birth; however, considerable interindividual variability is observed in the immediate postnatal (1,6 months) onset or increase in expression of these enzymes, often resulting in a window of hypervariability. © 2007 Wiley Periodicals, Inc. J Biochem Mol Toxicol 21:169,175, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20179 [source] | ||||||||||