Search results for "isoenzymes"
showing 10 items of 244 documents
Biotransformation of methylxanthines in mammalian cell lines genetically engineered for expression of single cytochrome P450 isoforms. Allocation of …
1993
V79 Chinese hamster cells genetically engineered for stable expression of single forms of rat cytochromes P450IA1, P450IA2, P450IIB1, human P450IA2, and rat liver epithelial cells expressing murine P450IA2 were used to allocate metabolic pathways of methylxanthines to specific isoforms and to test the suitability of such cell lines for investigations on drug interactions occurring at the cytochrome expressed. The cell lines were exposed to caffeine and/or theophylline and concentrations of metabolites formed in the medium were determined by HPLC. Caffeine was metabolized by human, rat and murine P450IA2, resulting in the formation of four primary demethylated and hydroxylated metabolites. H…
Interaction of Mitogen-activated Protein Kinases with the Kinase Interaction Motif of the Tyrosine Phosphatase PTP-SL Provides Substrate Specificity …
1999
ERK1 and ERK2 associate with the tyrosine phosphatase PTP-SL through a kinase interaction motif (KIM) located in the juxtamembrane region of PTP-SL. A glutathione S-transferase (GST)-PTP-SL fusion protein containing the KIM associated with ERK1 and ERK2 as well as with p38/HOG, but not with the related JNK1 kinase or with protein kinase A or C. Accordingly, ERK2 showed in vitro substrate specificity to phosphorylate GST-PTP-SL in comparison with GST-c-Jun. Furthermore, tyrosine dephosphorylation of ERK2 by the PTP-SLDeltaKIM mutant was impaired. The in vitro association of ERK1/2 with GST-PTP-SL was highly stable; however, low concentrations of nucleotides partially dissociated the ERK1/2.P…
Identification of a third secondary carrier (DcuC) for anaerobic C4-dicarboxylate transport in Escherichia coli: roles of the three Dcu carriers in u…
1996
In Escherichia coli, two carriers (DcuA and DcuB) for the transport of C4 dicarboxylates in anaerobic growth were known. Here a novel gene dcuC was identified encoding a secondary carrier (DcuC) for C4 dicarboxylates which is functional in anaerobic growth. The dcuC gene is located at min 14.1 of the E. coli map in the counterclockwise orientation. The dcuC gene combines two open reading frames found in other strains of E. coli K-12. The gene product (DcuC) is responsible for the transport of C4 dicarboxylates in DcuA-DcuB-deficient cells. The triple mutant (dcuA dcuB dcuC) is completely devoid of C4-dicarboxylate transport (exchange and uptake) during anaerobic growth, and the bacteria are…
Tonoplast subcellular localization of maize cytochrome b5 reductases
2000
Plant cytochrome b 5 reductases (b 5 R) are assumed to be part of an ER-associated redox chain that oxidizes NADH to provide electrons via cytochrome b5 (cyt b 5 ) to ER-associated fatty acyl desaturase and related hydroxylases, as in mammalian cells. Here we report on cDNA cloning of a novel maize b 5 R, NFR II, strongly related to a previously cloned cDNA, NFR I (Bagnaresi et al., 1999, Biochem, J. 338, 499-5051. Maize b 5 R isoforms are produced by a small multi-gene family. The NFR cDNAs were shown to encode active b 5 Rs by heterologous expression in yeast. Both reductases, in addition to Fe 3+ -chelates, efficiently reduced Cu 2+ -chelates. Using a polyclonal antibody able to recogniz…
Separation of deoxyribonucleases (DNases) of normal human stratum corneum and psoriatic scales by micro-disc-electrophoresis.
1975
Normal stratum corneum and psoriatic scales were homogenized and a differential centrifugation was performed. The DNase activity of the individual fractions was investigated by micro-disc-electrophoresis. At pH 5 only in the 600 × g pellet and 105.000 × g supernatant of normal keratin DNase activity could be observed. However, all psoriatic fractions showed distinct enzyme activities. At pH 7.4 little psoriatic DNase activity could only be demonstrated in the 105.000 × g supernatant. Except from the 15.000 × g pellet all fractions of normal stratum corneum displayed marked activities. In addition the 105.000 × g supernatant showed two different DNase bands.
Hypoxia: Importance in tumor biology, noninvasive measurement by imaging, and value of its measurement in the management of cancer therapy
2006
The Cancer Imaging Program of the National Cancer Institute convened a workshop to assess the current status of hypoxia imaging, to assess what is known about the biology of hypoxia as it relates to cancer and cancer therapy, and to define clinical scenarios in which in vivo hypoxia imaging could prove valuable.Hypoxia, or low oxygenation, has emerged as an important factor in tumor biology and response to cancer treatment. It has been correlated with angiogenesis, tumor aggressiveness, local recurrence, and metastasis, and it appears to be a prognostic factor for several cancers, including those of the cervix, head and neck, prostate, pancreas, and brain. The relationship between tumor oxy…
The pyrrole moiety as a template for COX-1/COX-2 inhibitors
2000
Aroyl- and thiophene-substituted pyrrole derivatives have been synthesized as a new class of COX-1/COX-2 inhibitors. The inhibition of COX-1 was evaluated in a biological system using bovine PMNLs as the enzyme source, whereas LPS-stimulated human monocytes served as the enzyme source for inducible COX-2. The determination of the concentration of arachidonic acid metabolites was performed by HPLC for COX-1 and RIA for COX-2. Variation of the substitution pattern led to a series of active compounds which showed inhibition for COX-1 and COX-2. Structural requirements for the development of COX-1/COX-2 inhibitors are discussed.
CYP3 phylogenomics: evidence for positive selection of CYP3A4 and CYP3A7.
2008
CYP3A metabolizes 50% of currently prescribed drugs and is frequently involved in clinically relevant drug interactions. The understanding of roles and regulations of the individual CYP3A genes in pharmacology and physiology is incomplete.Using genomic sequences from 16 species we investigated the evolution of CYP3 genomic loci over a period of 450 million years.CYP3A genes in amniota evolved from two ancestral CYP3A genes. Upon the emergence of eutherian mammals, one of them was lost, whereas, the other acquired a novel genomic environment owing to translocation. In primates, CYP3A underwent rapid evolutionary changes involving multiple gene duplications, deletions, pseudogenizations, and …
X-ray crystallography-promoted drug design of carbonic anhydrase inhibitors.
2015
1-N-Alkylated-6-sulfamoyl saccharin derivatives were prepared and assayed as carbonic anhydrase inhibitors (CAIs). During X-ray crystallographic experiments an unexpected hydrolysis of the isothiazole ring was evidenced which allowed us to prepare highly potent enzyme inhibitors with selectivity for some isoforms with medical applications.
Drug-metabolizing enzymes in the skin of man, rat, and pig.
2007
The mammalian skin has long been considered to be poor in drug metabolism. However, many reports clearly show that most drug metabolizing enzymes also occur in the mammalian skin albeit at relatively low specific activities. This review summarizes the current state of knowledge on drug metabolizing enzymes in the skin of human, rat, and pig, the latter, because it is often taken as a model for human skin on grounds of anatomical similarities. However only little is known about drug metabolizing enzymes in pig skin. Interestingly, some cytochromes P450 (CYP) have been observed in the rat skin which are not expressed in the rat liver, such as CYP 2B12 and CYP2D4. As far as investigated most d…