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1.
A strain of Rhodococcus designated MB1, which was capable of utilizing cocaine as a sole source of carbon and nitrogen for growth, was isolated from rhizosphere soil of the tropane alkaloid-producing plant Erythroxylum coca. A cocaine esterase was found to initiate degradation of cocaine, which was hydrolyzed to ecgonine methyl ester and benzoate; both of these esterolytic products were further metabolized by Rhodococcus sp. strain MB1. The structural gene encoding a cocaine esterase, designated cocE, was cloned from Rhodococcus sp. strain MB1 genomic libraries by screening recombinant strains of Rhodococcus erythropolis CW25 for growth on cocaine. The nucleotide sequence of cocE corresponded to an open reading frame of 1,724 bp that codes for a protein of 574 amino acids. The amino acid sequence of cocaine esterase has a region of similarity with the active serine consensus of X-prolyl dipeptidyl aminopeptidases, suggesting that the cocaine esterase is a serine esterase. The cocE coding sequence was subcloned into the pCFX1 expression plasmid and expressed in Escherichia coli. The recombinant cocaine esterase was purified to apparent homogeneity and was found to be monomeric, with an M(r) of approximately 65,000. The apparent K(m) of the enzyme (mean +/- standard deviation) for cocaine was measured as 1.33 +/- 0.085 mM. These findings are of potential use in the development of a linked assay for the detection of illicit cocaine.  相似文献   

2.
A strain of Pseudomonas maltophilia (termed MB11L) which was capable of using cocaine as its sole carbon and energy source was isolated by selective enrichment. An inducible esterase catalyzing the hydrolysis of cocaine to ecgonine methyl ester and benzoic acid was identified and purified 22-fold. In the presence of the solubilizing agent cholate, cocaine esterase had a native Mr of 110,000 and was shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be a monomer. In the absence of cholate, cocaine esterase had a native Mr of 410,000 and probably existed as a tetramer. The pH optimum of the enzyme was 8.0, and the Km values for cocaine, ethyl benzoate, and ethyl 2-hydroxybenzoate were 0.36, 1.89, and 1.75 mM, respectively. Inhibition studies indicated that the enzyme was a serine esterase, possibly possessing a cation-binding site similar to those of mammalian acetylcholinesterase and the atropine esterase of Pseudomonas putida PMBL-1. The cocaine esterase of P. maltophilia MB11L showed no activity with atropine, despite the structural similarity of cocaine and atropine.  相似文献   

3.
In 1-, 2- to 3-, 7- to 8-, and 10-day old intact and spinal rat puppies, studies have been made of the effect of l-DOPA (100 mg/kg, intraperitoneally) on autogenic periodic motor activity in the gastrocnemius muscle. In 1- to 3-day old pups, strong stimulating effect was observed up to a prolonged continuous activity for 5-10 or even more minutes. This effect decreases with age. Traces of the inhibitory effect are observed at early stages in the form of total decrease of the activity. The inhibitory effect increases with age. In all spinal animals, at the background of a decreased activity, stimulating effect of l-DOPA was predominantly observed. Age peculiarities of the effect of l-DOPA are discussed in relation to ontogenetic development of catecholaminergic innervation in rats. It is suggested that stimulating effect of l-DOPA is associated with its action on the descending noradrenergic system, whereas the inhibitory one is mediated by the brain structures.  相似文献   

4.
Apart from showing involvement of dopamine, recent studies also indicate a role of serotonin (5-HT) in the behavioral effects of cocaine in rodents. In the present study we investigated the role of 5-HT2A/2C receptors in the development or expression of sensitization to cocaine in rats, using ketanserin, an antagonist at these receptors. Since ketanserin also shows a high affinity for alpha1-adrenoceptors, prazosin, a comparative antagonist at those receptors was also examined. Male Wistar rats were treated repeatedly (for 5 days) with cocaine (10 mg/kg) in combination with either vehicle, or ketanserin (1-3 mg/kg) or prazosin (3 mg/kg); afterwards, on day 10, they received a challenge dose of cocaine (10 mg/kg). In another experiment, the animals were given either with vehicle or cocaine (10 mg/kg) for 5 days, and were then challenged with cocaine (10 mg/kg) in combination with vehicle, or ketanserin (1-3 mg/kg) or prazosin (3 mg/kg) on day 10. Acute administration of cocaine increased the locomotor activity in rats; that hyperactivation was inhibited by ketanserin (3 mg/kg), but not by prazosin. In animals treated repeatedly with cocaine, the locomotor hyperactivity induced by a challenge dose of the psychostimulant was ca. 2-3 times higher than that after its first administration. No difference was observed in the response to cocaine challenge in rats treated repeatedly with cocaine, ketanserin+cocaine, or prazosin+cocaine. In animals treated repeatedly with the psychostimulant, the behavioral response to a challenge dose of cocaine was dose-dependently decreased when the drug was combined with ketanserin, but not with prazosin. The above findings indicate a role of 5-HT2A/2C receptors (but not alpha1-adrenoceptors) in the acute locomotor hyperactivity, as well as in the expression (but not development) of cocaine sensitization. Since chronic use of cocaine by humans may lead to psychoses or craving for this drug of abuse, our findings also seem to indicate possible importance of 5-HT2A/2C receptor antagonists in the therapy of cocaine addiction.  相似文献   

5.
Carbonic anhydrase (CA) was purified from bovine erythrocyte plasma membrane and characterized in this study. For this purpose, the blood taken from young animals was hemolysed, the membrane fraction was separated, and this fraction was repeatedly washed. The enzyme (CA) was removed from the membrane with buffered TritonX-100 (1%); it could be purified at a factor of 22.8 by affinity chromatography.The CA obtained from erythrocyte membrane has an esterase activity as well as hydratase activity. The Vmax and Km of the enzyme for the substrate (p-nitrophenyl acetate) are 1.948x10(-3) mM/L x dak, and 3.596 mM, respectively. The purification degree of the enzyme was controlled by SDS-PAGE (3-10), which showed two distinct bands. It was determined that the enzyme had activity within the pH range of 4.5-9.5 and that the optimal pH was 7.5. The temperature at which it showed activity was 20-60 degrees C and optimal temperature was 37 degrees C. Molecular weight of CA was found to be 29844 and 61706 Dalton by gel filtration. On the other hand, sulfanilamide and acetazolamide affected the enzyme.  相似文献   

6.
Protein extracts from roots of chickpea (Cicer arietinum L.) plants contained high esterase activity hydrolyzing malonate hemiesters of isoflavone 7-O-glucosides. Using 5,7-dihydroxy-4'-methoxyisoflavone (biochanin A) 7-O-glucoside-6"-malonate as a substrate, a specific malonylesterase was purified about 700-fold to near homogeneity. The purified enzyme possesses an extremely low enzyme activity with synthetic esterase substrates. Various putative nonspecific esterases, as tested with alpha-naphthylacetate, were removed during enzyme purification. The malonylesterase demonstrated a very high molecular mass in gel chromatography and in sedimentation analyses with sucrose gradients (greater than or equal to 2 X 10(6)). Analytical sodium dodecyl sulfate-polyacrylamide gel electrophoresis pointed to a single subunit of 32,000. The catalyzed reaction showed a pH optimum at 7.5 and a temperature optimum between 30 and 35 degrees C. The apparent Km for biochanin A 7-O-glucoside-6"-malonate was (4.2 +/- 1.2) X 10(-4) M. The malonylesterase was insensitive to the esterase inhibitors eserine and neostigmine (10(-3) M) as well as phenylmethylsulfonyl fluoride, paraoxon, and diisopropylfluorophosphate (10(-4) M). On the other hand enzyme activity was totally inhibited by Hg2+ ions (10(-5) M) and p-hydroxymercuribenzoate (10(-4) M), whereas iodoacetamide (10(-6)-10(-4) M) inhibited only partially. Di- and tricarboxylic acids strongly stimulated enzyme activity at 10(-2) M. These properties indicate that the malonylesterase from chickpea roots greatly differs from other known esterases. The possible biological function of the specific malonylesterase is discussed in relation to isoflavone conjugate metabolism in chickpea.  相似文献   

7.
An attempt has been made to correlate the rapid effect of luteinizing hormone on testicular steroid production in vivo with testicular steroid concentrations and in vitro steroid production rates in testis tissue preparations. Within 20 min after intravenous administration of 25 mug luteinizing hormone, increases were observed in testosterone concentrations in testicular venous plasma and in whole testis tissue and in pregnenlone concentrations isolated testis mitochondrial fractions. Testosterone production by whole testis homogenates and pregnenolone production by isolated mitochondrial fractions were significantly increased within 5 min after in vivo administration of luteinizing hormone. Injection of cycloheximide 10 min prior to luteinizing hormone prevented the stimulating effect of luteinizing hormone to steroid levels in testicular venous plasma and testis tissue and on steroid production rates by preparations of rat testis tissue. Cycloheximide treatment of control animals did not significantly alter testosterone concentrations and testosterone production rates vitro, although mitochondrial pregnenolone concentrations and production rates were decreased. Testosterone production by whole testis homogenates as well as the pregnenolone production by isolated mitochondrial fractions obtained from luteinizing hormone treated testes and control glands showed a biphasic time curve A period (5-10 min) of high steroid production was followed by a period lower steroid production. Addition of 25 mug luteinizing hormone or 10(-8)--10(-5) M adenosine 3':5'-monophosphate (cyclic AMP) to the incubation medium had no effect pregnenolone production by isolated mitochondrial fractions. Administration of leuteinizing hormone in vivo markedly enhance the stimulating effect of Ca2+ on testosterone production by whole testis homogenates and on pregnenolone production by isolated mitochondrial fractions.  相似文献   

8.
9.
V F Bezrukov 《Genetika》1987,23(7):1290-1298
The term "pseudopolymorphism" refers to a situation, where there is no simple correspondence between genotype and phenotype: a single genotype may be moulded into several phenotypes. It is known that broad substrate specificity of enzymes may be one of the causes for pseudopolymorphism. This article deals with the other cause for this phenomenon--a consequence of post-translation modifications, such as limited proteolysis. Variability of some enzymes of grass carp Ctenopharyngodon idella Val. (Pisces, Cyprinidae) was studied by gel electrophoresis. It was found that variability of isozyme patterns of lactate dehydrogenase (LDH), glucose-6-phosphate dehydrogenase (G-6-PDH), malic enzyme (ME) and esterase (EST) is connected with the differences in protease activity of grass carp liver homogenates. The fish isozyme patterns of high (and, partially, intermediate) proteinase activity had some anomalies: displacement of fractions, one or several additional fractions, decreased activity of single fractions or the whole spectrum. In some cases, this variability looked like a classical polymorphic system specified by two alleles of one locus. The effect of enzymes' and proteins' modifications on electrophoretical pseudopolymorphism is discussed.  相似文献   

10.
Biological activity of lipid fractions of actinomycetes was examined on microorganisms and laboratory animals. The anabolic effect of the acetone fraction of Actinomyces aurigineus 2377 (on Wistar female rats), anabolic effect of sterols of Actinomyces griseus 15 (on chicks), and the high growth stimulating effect (up to 40-60%) of sterols of Actinomyces canosus 89 (on rats) were noted. The estrogenic effect of sterols of Act. griseus 15, Act. griseus 20 and Act. albodenitrificans 13a on the sex system was shown. The antimicrobial properties of lipid fractions differed in their selectivity with respect to the test organisms and depended also on the actinomycete species and cultivation conditions.  相似文献   

11.
Subcellular fractionation of liver homogenates from treated rats was carried out in order to study the mechanism of action of the gastrointestinal polypeptides on glucoronidation. Rats were treated for 90 min with an intravenous infusion of secretin (0.4 cU/h/100 g body weight), glucagon (100 micrograms/h/100 g body weight) and vasoactive intestinal polypeptide (VIP) (300 ng/h/100 g body weight); controls were sham-treated rats. For comparison, another group of animals was treated with a daily injection of phenobarbitone (10 mg/kg), a well-established enzyme inducer. Treatment with the different polypeptides produced minor changes in the subcellular localization of the enzyme. The bulk of activity was always recovered in the microsomal fraction, as identified by both differential centrifugation and the enrichment in specific activity of glucose-6-phosphatase, esterase and NADPH-cytochrome c reductase. Secretin produced a specific increase of bilirubin glucuronidation, more evident in all nuclear fractions. Glucagon increased both bilirubin and p-nitrophenol glucuronidation in all subcellular fractions. VIP had a selective action on p-nitrophenol conjugation of similar extent in nuclear and microsomal fractions. The type of changes observed is suggestive of physicochemical modifications occurring into the cell, perhaps at the membrane environment of different organelles, able to modify the overall conjugation of different substrates by the cell.  相似文献   

12.
A non-kallikrein arginine esterase (esterase I) has been purified from dog urine and characterized. The enzyme was purified by a three-step procedure, including ion exchange chromatography on DEAE-Sephacel, affinity chromatography on p-aminobenzamidine-Sepharose, and final gel filtration on Ultrogel AcA-54. The purified preparation gave three protein bands on polyacrylamide gel electrophoresis, all of which had esterolytic activity. The enzyme has a specific activity of 601 esterase units/mg protein. It has negligible kininogenase activity. Esterase I gave two closely migrating protein bands on reduced sodium dodecyl sulfate-polyacrylamide gel electrophoresis with molecular weights of 34,000 and 33,300. Esterase I is a glycoprotein with a pH optimum of 9.5 and a pI of 4.62. The enzyme is strongly inhibited by a host of inhibitors including aprotinin, leupeptin, antipain, soybean trypsin inhibitor, lima bean trypsin inhibitor, and DPhe-Phe-Arg-chloromethyl ketone (I50 in the 10(-9)-10(-8) M range). However, p-aminobenzamidine, N alpha-p-tosyl-lysyl chloromethyl ketone and phenylmethylsulfonyl fluoride were weak inhibitors, with I50 values in the 10(-5)-10(-7) M range. The enzyme preferentially hydrolyzes Pro-Arg bonds. Among fluorogenic substrates used in this study, butyloxycarbonyl-Val-Pro-Arg-methylcoumarinamide (alpha-thrombin substrate) was found to be the best, with a Km of 1.7 microM and a kcat/Km of 6.3 s.microM-1. However, esterase I does not convert fibrinogen to fibrin nor activate plasminogen to plasmin. Esterase I is immunologically distinct from dog urinary kallikrein, having no cross-reactivity with antibodies against dog kallikrein.  相似文献   

13.
A trypsin-like proteinase was localized within a single subcellular compartment of unfertilized Strongylocentrotus purpuratus eggs, the cortical granules. Homogenates of eggs were fractionated by rate-zonal centrifugation. Enzymatic markers were used to determine the distribution of mitochondria (cytochrome oxidase), yolk platelets (acid nitrophenyl phosphatase), and cortical granules (β-1, 3-glucanase) in the sucrose density gradient. A bimodal distribution pattern was obtained for aryl esterase activity (substrate: β-naphthyl acetate), with one peak in the microsomal and the other in the cortical granule fractions. The cortical granule enzyme was characterized as a trypsin-like proteinase, since it also hydrolyzed another typical tryptic substrate α-N-benzoyl-l-arginine ethyl ester and was completely inactivated by soybean trypsin inhibitor (SBTI). The aryl esterase activity in the microsomal fractions was not inhibited by SBTI, while 50% of the total aryl esterase activity in the original egg homogenate was inactivated by SBTI. The identity of the enzyme(s) responsible for the aryl esterase activity associated with the microsomal particles is unknown at present.The cortical granule proteinase functions in the elevation of the fertilization membrane and establishment of the block to polyspermy at fertilization. Arbacia punctulata eggs inseminated in the presence of trypsin inhibitors, SBTI or tosyl lysine chloromethyl ketone (TLCK), failed to elevate normal fertilization membranes and became heavily polyspermic.On the basis of these results and observations made by other investigators with a wide variety of biological systems, it is proposed that trypsin-like proteinases function in the discharge of secretory granules from all types of cells.  相似文献   

14.
Salinisphaera sp. P7-4 was isolated from the intestine of silver whiting, Sillago japonicas caught in the Pacific Ocean, and the esterase gene was cloned using the shotgun method. The amino acid sequence deduced from the nucleotide sequence (951 bp) corresponded to a protein of 316 amino acid residues with a molecular weight of 34,443. The esterase had 46 and 44% identities with the esterase enzymes of Ralstonia eutropha JMP134 and Rhodopseudomonas palustris HaA2, respectively. The primary structure of P7-4 esterase showed the conserved catalytic triad (Ser, Asp, His), consensus pentapeptide GXSXG, and oxyanion hole sequence (HG). The protein P7-4 was successfully expressed in Escherichia coli in a biologically active form. The enzyme showed high catalytic activity at low temperatures (5-25° C) with an activation energy of 2.18 kcal/mol. This result indicated that the esterase from Salinisphaera sp. P7-4 is a new cold-adapted enzyme. The enzyme preferentially hydrolyzed acyl-group chains with short chain lengths of ≤10 carbon. Metal ions such as Cd2(+), Co2(+), Cu2(+), Hg2(+), Ni2(+) and Zn2(+) inhibited enzymatic activity. Additionally, EDTA has no effect on its activity, whereas inhibition was observed with PMSF, a serine hydrolase inhibitor.  相似文献   

15.
The kinetics of inhibition of the esterase and lipase activities of bovine milk lipoprotein lipase (LPL) were compared. The esterase LPL activity against emulsified tributyrylglycerol was not affected by the enzyme activator apolipoprotein C-II (C-II) and amounted to about 15% of the "plus activator" lipase enzyme activity. Heparin at concentrations of 20 micrograms/ml inhibited 25% of the esterase activity. The reaction followed Henri-Michaelis-Menten kinetics and the inhibition by heparin followed a linear, intersecting, noncompetitive kinetic model. On the other hand, the basal lipase activity of LPL against emulsified trioleoylglycerol (TG) was very sensitive to inhibition by heparin: 1 microgram/ml inhibited about 80% of the reaction and 3 micrograms/ml drove the reaction to zero. The velocity curve for the uninhibited basal LPL activity was sigmoidal with an apparent nH(TG) of 2.94. Heparin inhibited the lipase activity competitively: heparin decreased nH(TG) and increased[TG]0.5 6.4-fold, while TG decreased the nH(Heparin) from 2.14 to 0.95 and caused a 3-fold increase in [Heparin]0.5. C-II, at concentrations lower than 2.5 X 10(-8) M (i.e., lower than KA), countered the inhibitory effects of heparin: at constant inhibitor concentrations, C-II increased nH(TG) from 1.78 to 2.52 and decreased [TG]0.5 about 10-fold; it also increased the apparent Vmax. At the lower C-II concentrations, nH(C-II) was approximately equal to 1.0 and increasing the TG concentrations decreased [C-II]0.5 from 3.8 X 10(-8) to 8.5 X 10(-9) M, with no effect on the nH(C-II). At the higher C-II concentrations, nH(C-II) was 2.5 and TG decreased [C-II]0.5 about 2-fold with no effect on the nH(C-II). In the absence of heparin, C-II had no effect on nH(TG) nor on [TG]0.5, but it increased the apparent Vmax. On the other hand, TG had no effect on nH(C-II) nor on [C-II]0.5, but at any given C-II concentration, the reaction velocity increased with increasing TG concentrations. It is concluded that TG and heparin as well as C-II and heparin are mutually exclusive and that lipoprotein lipase is a multisite enzyme, possibly a tetramer, with three high-affinity catalytic sites, and an equal number of sites for C-II and heparin per oligomer. However, LPL differs from classical allosteric enzymes in that its activator has no effect on substrate cooperativity nor on [S]0.5; its only effect is to increase Vmax by increasing the catalytic rate constant kp by inducing conformational changes in the enzyme.  相似文献   

16.
The influence of cocaine on tyrosine hydroxilase of rat brain hypothalamus was investigated in vivo (0.5 mg/kg) and in vitro (10(--6)--10(--5)M). Cocaine was used as a substance with a known adrenergic type of action. It was shown that under standard conditions cocaine in vitro increased the enzyme activity and decreased the Km for DMPH4 cofactor without changing Vmax of the reaction analyzed by the membrane enzyme. Cocaine in vitro decreased the tyrosine hydroxylase activity, especially that of the membrane enzyme. In this case there occurred a decrease of Km for DMPH4 and a decrease of Vmax of the reaction. The decrease of Vmax is considered to be the result of the secondary effect of cocaine.  相似文献   

17.
Intratesticular injection of epinephrine and norepinephrine caused stimulation of ornithine decarboxylase (ODC) activity in the testis of immature rat. The effect of epinephrine was time and dose dependant. The minimal effective dose for epinephrine was found to be 100 pg and optimal stimulation was observed with 500 ng of the drug. Maximal stimulation of ODC occurred at 2 h after the treatment and reduced significantly at 4 h reaching to control levels at 6 h. Simultaneous injection of epinephrine with dibutyryl cAMP, luteinizing hormone, follicle stimulating hormone or prostaglandin E2 caused additional stimulation of the enzyme activity. Injection of epinephrine to norepinephrine treated animals caused additional effect. Both epinephrine and norepinephrine were found to stimulate the enzyme activity in leydig cell and seminiferous tubule fractions. These results suggest that catecholamines are also involved in the regulation of ODC activity in the testis of rat.  相似文献   

18.
Esterase A is one of the esterase isozymes in eggs of Bombyx mori. The effect of this esterase A on the yolk cells of diapause eggs was examined with a hanging-drop culture in order to discover the mechanism of diapause termination in silkworm eggs.The culture of yolk cells in diapause eggs shows spherical forms with dark fine grains in the central parts, large translucent granules in the outer parts, and a membrane on the exterior. When such yolk cells were incubated with yolk materials of acid-treated or diapause-terminated eggs, they were damaged and cell lysis occurred. This suggested that substance(s) causing the cell lysis were present in diapause-terminated eggs. When esterase A separated electrophoretically from non-diapause eggs and diapause-terminated eggs was added to hanging-drop cultures of yolk cells of diapause eggs, the yolk cells were also greatly affected. That is, a part of the yolk cell membrane was dissolved or disappeared, and the central dark fine grains diffused over the cell causing the whole cell to become dark. A few cells lost almost all of their contents and collapsed. Other esterase fractions and fractions without esterase activity in the electrophoresis exerted little effect on the yolk cells. Furthermore, a parallelism between esterase activity to hydrolyse 2-naphthyl acetate as substrate and the lytic activity on the yolk cell membrane was observed in this esterase A fraction from different sources.From these results it is highly probable that the substance responsible for cell lysis is the esterase A enzyme itself. Diapause termination of silkworm eggs is discussed in relation to the lysis of yolk cells.  相似文献   

19.
A product of histamine-stimulated human lymphocytes, histamine-induced suppressor factor or HSF, was characterized by enzyme treatment, sensitivity to reduction and alkylation, by molecular sieve chromatography, and by polyacrylamide gel electrophoresis. HSF was found to have a wide pH stability (pH 3-10), sensitivity to temperatures greater than 80 degrees C, and to have the properties of a glycoprotein by virtue of its sensitivity to chymotrypsin, trypsin, sodium periodate, and neuraminidase. HSF did not appear to have a serine group(s) in its "active" site since its biologic activity remained intact following treatment with an irreversible serine esterase inhibitor (phenylmethylsulfonyl fluoride). Further, HSF did not appear to have inter- or intra-molecular disulfide linkages because treatment with denaturing and/or reducing agents, followed by alkylation, did not significantly alter its activity. Molecular sieve chromatography employing Sephadex G-100 revealed an apparent molecular weight for HSF of 25-40,000. Electrophoresis of HSF in polyacrylamide gels at pH 8.7 under nonreducing conditions revealed two regions of activity, one region migrating with albumin and the other region anodal to albumin. In addition to suppressing lymphocyte proliferation, the 25-40,000 Mr Sephadex G-100 fractions also inhibited the production of leukocyte inhibitory factor. Of particular interest, gel filtration of supernatants generated by stimulating mononuclear cells with either histamine, dimaprit (but not 2-pyridylethylamine), concanavalin A, or candida albicans resulted in similar elution profiles with regard to inhibition of lymphocyte proliferation. That is, 25-40,000 Mr fractions of supernatants generated by each stimulant suppressed lymphocyte proliferation to a similar degree. The latter findings provide indirect evidence that T lymphocytes, triggered in response to antigen-specific and nonspecific stimuli, elaborate suppressor molecules capable of modulating T-cell function that share certain similarities.  相似文献   

20.
Bovine γ-globulin was separated into four fractions by chromatography on cellulose phosphate. The chromatographic distribution was similar to that reported for human and dog γ-globulin. More than 80% of a nonspecific phagocytosis stimulating factor (leucokinin) present in the serum was isolated in γ-globulin fraction IV. Bocine red blood cells and polymorphonuclear leukocytes bind γ-globulin without appreciable selectivity for any of the four chromatographic fractions, but they do selectively bind the phagocytosis stimulating factor. Splenectomy caused no observable change in either the chromatographic distribution or phagocytosis stimulating activity of bovine serum γ-globulin. The tetrapeptide tuftsin stimulates phagocytosis by bovine neutrophiles, but on a molar basis the activity of tuftsin was only 10% that of the phagocytosis stimulating factor. If the factor exerts its effect, as has been proposed, by having a phagocytosis stimulating peptide cleaved from it by an enzyme on the leukocyte membrane, that peptide must differ in structure from tuftsin. This conclusion is supported by the inability of trypsin to liberate an active peptide from bovine serum.  相似文献   

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