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1.
Analysis of starch-degrading enzymes in a crude extract of detached cotyledons of Pisum sativum L. by polyacrylamide gel electrophoresis (PAGE) demonstrated the presence of one band of -amylase (EC 3.2.1.1) activity. The activity of only this amylase was promoted in cotyledons incubated with 2,4-dichlorophenoxyacetic acid (2,4-D). The auxin-induced -amylase from pea cotyledons was purified to homogeneity, as judged by the criterion of a single band after PAGE. The relative molecular mass (Mr), estimated by gel filtration, was approx. 42 000 and the enzyme contained no carbohydrate moiety. Sodium dodecylsulfate-PAGE yielded a single band that corresponded to an Mr of 41 000. The isoelectric point was 5.85 and the aminoacid composition was similar to that of -amylase from other plants. When [3H]leucine was fed to detached dry cotyledons prior to incubation, the radioactivity in -amylase from cotyledons incubated in the presence of 2,4-D was found to be approx. 10-fold higher than that from cotyledons incubated in distilled water. When -amylase from cotyledons incubated with 2H2O that contained 2,4-D and the tritiated amylase were centrifuged together in a CsCl density gradient, the peak of enzymatic activity of deuterated -amylase was shifted to a denser fraction than the peak of radioactivity of the tritiated enzyme. These results show that auxin-induced -amylase in pea cotyledons is synthesized de novo.Abbreviations 2,4-D
2,4-dichlorophenoxyacetic acid
- Mr
relative molecular mass
- PAGE
polyacrylamide gel electrophoresis
- PAS
periodic acid-Schiff
- pI
isoelectric point
- SDS
sodium dodecyl sulfate
We are very grateful to Mr. Kazuo Itoh and Mrs. Matsumi Doe for carrying out the analysis of amino-acid composition. 相似文献
2.
Henk J. M. Aarts Eldine H. M. Jacobs Gijsbert van Willigen Nicolette H. Lubsen John G. G. Schoenmakers 《Journal of molecular evolution》1989,28(4):313-321
Summary We have determined the sequence of a rat A3/A1-crystallin complementary DNA (cDNA) clone and the (partial) sequence of the human B3-crystallin gene. Calculation of the ratio of silent to nonsynonymous substitution between orthologous A3/A1-, B3-, and other - and -crystallin sequences revealed that the region encoding the two globular domains of the A3/A1-crystallin sequence is the best conserved during evolution, much better than the corresponding region of the B1-, B3-, or the -crystallin sequences, and even better (at least in the rodent/frog comparison) that the well-conserved A-crystallin sequence. Remarkably, the rate of change of the A3/A1-crystallin coding sequence does not differ in the rodent and primate lineages, in contrast with previous findings concerning the evolution rates of the A- or -crystallin sequences in these two lineages. Comparison of the regions that encode the four motifs of the -crystallin between orthologous mammalian sequences showed that the extent of nonsynonymous substitution in each of these four homologous motif regions is the same. However, when the orthologous -crystallin genes of more distantly related species (mammals vs chicken or frog) are compared, the extent of nonsynonymous substitution is higher in the regions encoding the external motifs I and III than in the regions encoding the internal motifs II and IV. This phenomenon is also observed when paralogous members of the /-crystallin supergene family are compared. 相似文献
3.
Syndecan-4 is a transmembrane heparan sulfate proteoglycan belonging to the syndecan family. Syndecan-4-deficient [(Synd4(–/–)] mice were produced to clarify the in vivo role of syndecan-4. Synd4(–/–) mice were more susceptible to -carrageenan-induced nephropathy, and the placental labyrinth from the deficient embryos exhibited more thrombi than wild-type ones. Importantly, Synd4(–/–) mice were more susceptible to endotoxin shock. Further analysis revealed that the mechanism to suppress excessive production of interleukin-1 (1L-1) by transforming growth factor- (TGF-) was impaired in the deficient mice. TGF-, one of the cytokines involved in the suppression mechanism, bound to heparan sulfate chain of syndecan-4, which was induced in macrophages and the microvasculature after administration of lipopolysaccharide. Therefore, augmentation of TGF- function by induced syndecan-4 was suggested as a mechanism of the suppressive action of syndecan-4 against endotoxin shock. Published in 2003. 相似文献
4.
Copper(II) ,-dicarboxylate complexes of general formulae, [Cu(O2C(CH2)nCO2)]·xH2O, [Cu(O2C(CH2)nCO2) (phen)2]·xH2O and [Cu(O2C(CH2)nCO2)(bipy)y]·xH2O (n=1–8; y=1, 2; phen = 1,10-phenanthroline; bipy = 2,2-bipyridine) were synthesised. These copper complexes, some related manganese(II) complexes and the metal-free ligands were screened in vitro for their ability to inhibit the growth of Candida albicans. Metal-free 1,10-phenanthroline and all of the copper(II) and manganese(II) phenanthroline complexes were potent growth inhibitors, with only one bipyridine complex, [Cu(O2C(CH2)CO2)(bipy)2]·2H2O, having moderate activity. The remaining substances were effectively inactive. Complexes which were active against C. albicans also proved effective against C. glabrata, C. tropicalis and C. kreusi with the manganese complexes retaining superior activity. For the phenanthroline complexes the active drug species is thought to be the dication [M(phen)2(H2O)n]2+ (M = Cu, Mn). Escherichia coli and Staphylococcus aureus were resistant to all of the metal complexes and also to metal-free 1,10-phenanthroline. Only the copper phenanthroline complexes showed intermediate activity against Pseudomonas aeruginosa. 相似文献
5.
Substrate and inhibitor specificity of anion exchangers on the brush border membrane of rabbit ileum
Roy G. Knickelbein Peter S. Aronson John W. Dobbins 《The Journal of membrane biology》1985,88(2):199-204
Summary In previous studies we have found that several anions can be transported by an exchange process in rabbit ileal brush border membranes. We demonstrated exchanges of Cl for OH or HCO3, SO4 for OH, oxalate for OH, and oxalate for Cl. The purpose of these studies was to determine the number of distinct carriers mediating these exchanges. We utilized substrate and inhibitor specificity studies to distinguish between different anion exchange transporters. We conclude that SO4OH and oxalate: OH exchange occur on the same carrier because: (i) pH-gradient stimulated transport of both14C-oxalate and35SO4 were equally sensitive tocis-inhibition by unlabeled SO4 or oxalate; and (ii) both were inhibited equally by K. We conclude that oxalate: OH and oxalate: Cl exchanges occur on different carriers because: (i) Cl or SO4 caused unequalcis-inhibition of these two exchanges; and (ii) as compared to oxalate: Cl exchange, oxalate: OH exchange was more sensitive to inhibition by probenecid and K and less sensitive to inhibition by bumetanide. Finally, we conclude that oxalate: Cl exchange and ClHCO3 exchange occur on different carriers because: (i) ClHCO3 exchange was almost completely insensitive tocis-inhibition by oxalate; and (ii) oxalate: Cl exchange was more sensitive to inhibition by DIDS and bumetanide than ClHCO3 exchange. Thus we have found that there are at least three separate anion exchangers on rabbit ileal brush border: (i) a ClHCO3 exchanger; (ii) a SO4OH exchanger, which also transports oxalate; and (iii) an oxalate: Cl exchanger. 相似文献
6.
Summary We have investigated the pharmacokinetics, tolerance, and biological activity of recombinant human interferon- (rHuIFN) administered subcutaneously to cancer patients. Twenty-one patients with lymphoma and metastatic cancer received rHuIFN (in doses of 0.1, 0.25, or 0.5 mg/m2) in two or three injections per week for up to 180 days. The most common adverse effects encountered were flu-like symptoms, fever and fatigue. The increase in body temperature after each administration ranged from 0 to 4°C depending on the individual patient, but was unrelated to the rHuIFN dose or its plasma concentration. The pharmacokinetic response of the patients after the two treatments showed a low intra-individual variability with respect to the plasma concentration/time profiles. However, as observed for the fever side-effect, the interindividual variation (CV >50%) was high for the parameters area under the data points (AUC0-t
) and maximum plasma concentration (c
max). Despite this high interindividual variability, the mean values obtained for AUC0-t
andc
max after s.c. injection of rHuIFN were approximately proportional to the dose administered: the injection of 0.1, 0.25 or 0.5 mg/m2 rHuIFN resulted in AUC0-t
values of 15.4, 31.5 or 69.6 ng h/ml, respectively andc
max was found to be 1.0, 2.4 and 4.9 ng/ml, respectively. With this s.c. administration protocol, objective antitumour responses were observed in two patients, but there was no partial or complete remission. 相似文献
7.
8.
Sharon X. Chen Charles C. Hardin Harold E. Swaisgood 《Journal of Protein Chemistry》1993,12(5):613-625
Incubation of -lactoglobulin with immobilized trypsin at 5–10°C results in a time-dependent release of several fragments of the core domain in yields approaching 15%. Digests were fractionated by ion-exchange chromatography with a Mono Q HR5/5 column and analyzed after disulfide reduction by polyacrylamide gel electrophoresis in sodium dodecylsulfate. Three fragments with approximate molecular weights of 13.8, 9.6, and 6.7 kD were identified. The fraction from ion-exchange chromatography yielding the 6.7 kD fraction after disulfide reduction was further characterized because it was most homogeneous and gave the highest yield. The C-terminal cleavage site of the 6.7 kD core fragment appeared to be Lys100 or Lys101 as determined by C-terminal amino acid analysis. The exact masses, after reduction with dithiothreitol, are 6195 and 6926 as determined by laser desorption mass spectrometry, corresponding to residues 48–101 and 41–100. Prior to reduction, -lactoglobulin C-terminal residues 149–162 are connected to these core domain fragments as shown by C-terminal analysis and mass spectrometry. Structural studies indicate that these 7.9 and 8.6 kD core domain fragments released by immobilized trypsin retain much of their native structure. CD spectra indicate the presence of antiparallel -sheet structure similar to the native protein but the -helix is lost. Spectra in the aromatic region indicate the existence of tertiary structure. Moreover, structural transitions in urea are completely reversible as measured by CD spectra, although the extrapolated G
D
H20
and the urea concentration at the transition midpoint are lower than for the native protein. The core domain fragments also display apH-dependent binding to immobilizedtrans-retinal as does intact protein. A single endotherm is obtained for both core domain fragments and native protein upon differential scanning calorimetry, but again, the domain is less stable as indicated by a transition peak maxima of 56.9°C as compared with 81.1°C for native protein.Abbreviations used: CD, circular dichroism; CPG, controlled pore glass; DSC, differential scanning calorimetry; DTT, dithiothreitol; FPLC, fast flow liquid chromatography; HPLC, high-performance liquid chromatography; PITC, phenylisothiocyanate; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; TEA, triethylamine; UV, ultraviolet. 相似文献
9.
Tatsuya Inui József Bódi Hideki Nishio Yuji Nishiuchi Terutoshi Kimura 《Letters in Peptide Science》2001,8(6):319-330
Segment condensation reaction of sparingly soluble protected peptides proceeded smoothly in CHCl3-phenol mixed solvent without danger of epimerization or of significant ester formationwith the carboxyl component when 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) was employedin the presence of 3,4-dihydro-3-hydroxy-4-oxo-1,2,3-benzotriazine(HOOBt). The optimal conditions for enhancement of peptide coupling mediated by EDC/HOOBt in CHCl3-phenol were determined and successfully applied to the synthesis of amyloid -peptide (1-42), (1-43) and [Pyr3]-(3-42). These peptides of high homogeneity were used to examine the relation between structure and amyloidogenesis by means of CD spectra andfluorimetric assay. 相似文献
10.
The specificity of induction of cellulose- and xylan-degrading enzymes was investigated on the yeast strain Trichosporon cutaneum CCY 30-5-4 using series of compounds structurally related to cellulose and xylan, including monosaccharides, glycosides, glucooligosaccharides and xylooligosaccharides. Determination of activities of secreted cellulase and -xylanase, intracellular, cell wall bound and extracellular -glucosidase and -xylosidase revealed that: (1) The synthesis of xylan-degrading enzymes is induced in the cell only by xylosaccharides, 1,3--xylobiose, 1,2--xylobiose, 1,4--xylosyl-L-arabinose, 1,4--xylobiose and thioxylobiose being the best inducers. The xylan-degrading enzymes show different pattern of development in time and discrete cellular localization, i.e. intracellular -xylosidase precedes extracellular -xylanase. (2) A true cellulase is not inducible by glucosaccharides and cellulose. Negligible constitutive cellulase activity was detected which was about two orders lower than an induced cellulase in the typical cellulolytic fungus Trichoderma reesei QM 9414. (3) The best inducer of intracellular -glucosidase splitting cellobiose was thiocellobiose in a wide range of concentration (0.1–10 mM), whereas xylosaccharides at high concentrations induced -xylosidase of xylobiose type and a non-specific aryl -D-glucosidase.The results were confirmed by growing cells on cellulose and xylan. T. cutaneum was found to be a xylan-voracious yeast, unable to grow on cellulose. 相似文献
11.
Many N2-fixing organisms can turn off nitrogenase activity in the presence of NH4
+ and turn it on again when the NH4
+ is exhausted. One of the most interesting systems for accomplishing this is by covalent modification of one subunit of dinitrogenase reductase by dinitrogenase reductase ADP-ribosyltransferase (DRAT). The system can be reactivated when NH4
+ is exhausted, by dinitrogenase reductase activating glycohydrolase (DRAG) which removes the inactivating group. It is fascinating that some species of the genusAzospirillum possess the DRAT and DRAG systems (A. lipoferum andA. brasilense), whereasA. amazonense in the same genus lacks DRAT and DRAG.A. amazonense responds to NH4
+ but does not exhibit modification of dinitrogenase reductase characteristic of the action of DRAT. However, it has been possible to clone DRAT and DRAG and to introduce them intoA. amazonense, whereupon they become functional in this organism. The DRAT and DRAG system does not appear to function inAcetobacter diazotrophicus, an organism isolated from sugar cane, that fixes N2 at a pH as low as 3.0.A. diazotrophicus does show a rather sluggish response to NH4
+. A level of about 10 M NH4
+ is required to switch off the system. The response to NH4
+ is influenced by the dissolved oxygen concentration (DOC) as has been reported forAzospirillum sp. A DOC in equilibrium with 0.1 to 0.2 kPa O2 seems optimal for the response inA. diazotrophicus. 相似文献
12.
DNA polymerases II () and III() are the only nuclear DNA polymerases known to possess an intrinsic 3 5 exonuclease in Saccharomyces cerevisiae. We have investigated the spontaneous mutator phenotypes of DNA polymerase and 3 5 exonuclease-deficient mutants, pol3-01 and pol2-4, respectively. pol3-01 and pol2-4 increased spontaneous mutation rates by factors of the order of 102 and 101, respectively, measured as URA3 forward mutation and his7-2 reversion. Surprisingly, a double mutant pol2-4 pol3-01 haploid was inviable. This was probably due to accumulation of unedited errors, since a pol2-4/pol2-4 pol3-01/pol3-01 diploid was viable, with the spontaneous his7-2 reversion rate increased by about 2 × 103-fold. Analysis of mutation rates of double mutants indicated that the 3 5 exonucleases of DNA polymerases and can act competitively and that, like the 3 5 exonuclease of DNA polymerase the 3 5 exonuclease of DNA polymerase acts in series with the PMS1 mismatch correction system. Mutational spectra at a URA3 gene placed in both orientations near to a defined replication origin provided evidence that the 3 5 exonucleases of DNA polymerases and act on opposite DNA strands, but were in sufficient to distinguish conclusively between different models of DNA replication. 相似文献
13.
Huang Chi-Ying F. Yuan Chiun-Jye Livanova Nataliya B. Graves Donald J. 《Molecular and cellular biochemistry》1993,127(1):7-18
A catalytic fragment,
1-298, derived from limited chymotryptic digestion of phosphorylaseb kinase (Harris, W.R.et al., J. Biol. Chem., 265: 11740–11745, 1990), is reported to have about six-fold greater specific activity than does the subunit-calmodulin complex. To test whether there is an inhibitory domain located outside the catalytic core of the subunit, full-length wild-type and seven truncated forms of were expressed inE. coli. Recombinant proteins accumulate in the inclusion bodies and can be isolated, solubilized, renatured, and purified further by ammonium sulfate precipitation and Q-Sepharose column. Four out of seven truncated mutants show similar (
1-353 and
1-341) or less (
1-331 and
1-276) specific activity than does the full-length wild-type ,
1-386. Three truncated forms,
1-316,
1-300, and
1-290 have molar specific activities approximately twice as great as those of the full-length wild-type and the nonactivated holoenzyme. All recombinant s exhibit similarK
m values for both substrates, i.e., about 18M for phosphorylaseb and about 75 M for MgATP. Three truncated s,
1-316,
1-300, and
1-290, have a 1.9- to 2.5-fold greater catalytic efficiency (V
max/K
m) than that of the full-length wild-type and a 3.5- to 4.5-fold greater efficiency than that of the truncated
1-331. This evidence suggests that there is at least one inhibitory domain in the C-terminal region of , which is located at
301-331·
1-290, but not
1-276, which contains the highly conserved kinase domain, is the minimum sequence required for the subunit to exhibit phosphotransferase activity. Both
1-290 and
1-300 have several properties similar to full-length wild-type , including metal ion responses (activation by free Mg2+ and inhibition by free Mn2+) pH dependency, and substrate specificities. 相似文献
14.
Gijsbertus W. van Eijk Henri J. Roeijmans Hubertus A. van der Aa 《Antonie van Leeuwenhoek》1988,54(4):325-330
Clumps of white crystals present in 40-day-old malt agar cultures of Holwaya mucida were isolated as long white needles by crystallization from ethanol following short extraction with chloroform. The levorotary compound ([]
289
21
=-193.8°) was recognized as a -lactone (C17H20O5) by infrared and mass spectrometry. It was identified as 7-methoxy-3a, 10b-dimethyl-1, 2, 3, 3a, 5a, 7, 10b, 10c-octahydro-4H, 9H-furo[2, 3, 4 : 4, 5]naphtho[2, 1-c]pyran-4, 9-dione, a labdane-derived compound known as antibiotic LL-Z1271. Preparative thin-layer chromatography of the mother liquor afforded 2 minor metabolites. One was identified as LL-Z1271, the demethylated analogue of LL-Z1271. The other one named LL-Z1271, was recognized as a compound related to and : its structure could not be fully elucidated.
H. mucida (anamorph: Crinula calciiformis) has no taxonomic relationship with two other LL-Z1271 producing species viz. Acrostalagmus sp. (= Acremonium cf. atrogriseum) and Oidiodendron truncatum. 相似文献
15.
Jean-Marc Lelievre Craig D. Dickinson Liliane A. Dickinson N. C. Nielsen 《Plant molecular biology》1992,18(2):259-274
The construction of SP6-derived expression plasmids that encode normal and modified -conglycinin subunits is described. With the exception of an additional methionine at their NH2-terminal ends and the lack of glycans, the normal subunits synthesized at the direction of these plasmids coresponded to mature and subunits isolated from soybean seeds. The subunits assembled into trimers in vitro that were equivalent in size to those formed in vivo. This result shows that the glycans are not required either for protein folding or oligomer assembly. Subunits produced from other plasmids, which had modifications in a highly conserved hydrophobic region in the COOH-terminal end of the subunits, either did not assemble or assembled at an extremely low rate compared to unmodified subunits. Structural changes at the more hydrophilic NH2-terminal end had mixed effects. Several subunits modified in this region assembled into trimers at rates that were either equal or greater than those for normal subunits. Others assembled less completely than the normal subunits. Our results indicate that the in vitro synthesis and assembly assay will be useful in evaluating structure-function relationships in modified -conglycinin subunits. The results also show that structural changes at the NH2-terminal end of the subunits are tolerated to a greater extent than modifications in the hydrophobic conserved region in the COOH-terminal half of the subunits, and this information will be useful in efforts to improve soybean quality. 相似文献
16.
The thermophilic fungus Malbranchea sulfurea produces extracellular -amylase whereas -glucosidase is mainly cell bound. Extraction of the cell bound enzyme was maximum with one molar NaCl, followed by Triton ×100 and Urea-Na2SO3 extractants. Supplementation of Triton ×100 in growth medium significantly affected the presence of enzymes at various locations. A role for cell bound -amylase and -glucosidase has been suggested in rapid starch utilization by the fungus during early growth phase. 相似文献
17.
Endo--galactosidase (EC 3.2.1.103) ofBacteroides fragilis, at 250 mU ml–1, did not cleave the internal galactosidic linkage of the linear radiolabelled trisaccharide GlcNAc1-6Gal1-4GlcNAc, or those of the tetrasaccharides Gal1-4GlcNAc1-6Gal1-4GlcNAc and Gal1-4GlcNAc1-6Gal1-4Glc. The isomeric glycans which contained the GlcNAc1-3Gal1-4GlcNAc/Glc sequence were readily cleaved.Abbreviations GlcNAc
2-acetamido-2-deoxy-d-glucose
- Lact
lactose
- MT
maltotriose
- MTet
maltotetraose
-
R
MTet
chromatographic migration rate in relation to that of maltotetraose 相似文献
18.
The building up of the two types of reaction centers, PS II and PS II, was investigated during the greening of Euglena gracilis Z cells in resting medium. The maximal values in the proportion of PS II centers (55%) and in the oxygen evolved per chlorophyll were reached at the outbreak of greening, when accumulation of galactolipids (MGDG and DGDG) rich in unsaturated fatty acids occurred, and when anionic lipids (SQDG and PG) emerged. As the greening progressed, the chlorophyll accumulation corresponded to a secondary enrichment in PS II centers, which built up more rapidly than PS II centers; correlatively, a general saturation of the fatty acids constitutive of all lipid classes took place.Abbreviations DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- DGDG
digalactosyldiacylglycerol
- FAME
Tatty acid methyl esters
- HEPES
acide (N-[2-hydroxyethyl]piperazine-N-[2-ethane sulfonic]
- MGDG
monogalactosyldiacylglycerol
- PC
phosphatidylcholine
- PE
phosphatidylethanolamine
- PG
phosphatidylglycerol
- PQ
plastoquinone
- PS I
Photosystem I
- PS II
Photosystem II
- QA
primary quinone electron acceptor of PS II
- QB
secondary quinone electron acceptor of PS II
- SQDG
sulfoquinovosyldiacylglycerol 相似文献
19.
Experimental support for the use of fluid aqueous organic solvent systems and subzero temperatures in mechanistic studies of -galactosidase is presented. The enzyme was stable and retained catalytic activity and structural integrity in 50% aqueous dimethyl sulfoxide and 60% aqueous methanol at 0°C; at lower temperatures higher concentrations of cosolvent may be successfully used. The effects of dimethyl sulfoxide on the catalytic and structural properties of the enzyme were investigated in detail. For the -galactoside-catalyzed h ydrolysis ofo-nitrophenyl--D-galactoside the value ofk
cat decreased in a linear manner with increasing cosolvent concentration, whereasK
m increased exponentially. The decrease ink
cat paralleled the decrease in water concentration, consistent with rate-limiting hydrolysis of a galactosylenzyme intermediate. The increase inK
m is attributed to less favorable partitioning of the substrate to the active site in the cryosolvent compared to aqueous solution. ThepH*-rate profile for this reaction at 0°C in 50% dimethyl sulfoxide was similar to that in aqueous solution, withpK*1=5.8 andpK*2=8.0. Linear Arrhenius plots, with energies of activation of 13.9 and 16.0 kcal mol–1, respectively, were obtained for the -galactosidase-catalyzed hydrolysis ofo-nitrophenyl- andp-nitrophenyl--D-galactosides in 50% dimethyl sulfoxide at temperatures to –57°C. Examination of the intrinsic fluorescence and ultraviolet spectra of the enzyme as a function of increasing cosolvent concentration showed no evidence for structural perturbation up to and including 50% dimethyl sulfoxide at 0°C. We conclude that these cryosolvent systems are suitable for mechanistic investigations of -galactosidase, in particular for trapping intermediates at subzero temperatures. 相似文献
20.
Bhattacharyya S Ghosh S Sen P Roy S Majumdar S 《Molecular and cellular biochemistry》2001,216(1-2):47-57
Leishmania donovani, an obligate intracellular parasite resides and multiplies within macrophage of the reticuloendothelial system. The intracellular signalling mechanism involved in the impaired oxidative response in leishmaniasis has not yet been clearly established. Generation of superoxide anion (O2
–) is supposed to be the first line of host defence during microbial invasion. We found a substantial inhibition of superoxide anion generation in parasitized macrophages, which was just the reverse in case of macrophages challenged with Lipophosphoglycan (LPG) deficient attenuated leishmanial parasite UR-6. The generation of O2
– essentially needs the prior activation of protein kinase C (PKC) mediated phosphorylation events. Our study proposed that phosphorylation of 67, 54, 47 and 36 kDa proteins was attenuated during infection. This was supported by PKC activity study, where Ca-dependent PKC activity was inhibited but, Ca-independent PKC activity was enhanced. This result was further confirmed by using isotype specific pseudosubstrate inhibitors of Ca-dependent PKC and Ca-independent PKC . Application of -pseudosubstrate could not alter the Ca-dependent PKC activity but -pseudosubstrate inhibited the Ca-independent PKC activity in infected macrophages. Our immunoblot analysis with specific antibody against PKC and PKC isotypes showed down regulation of PKC -II expression with concomitant induction of PKC . Such inhibition of Ca-dependent PKC was reversed in macrophages treated with UR-6. Taken together, our observations revealed that infection with L. donovani selectively attenuates both the expression and activity of Ca-dependent PKC . 相似文献