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1.
Makio Morita Hiroshi Eguchi Makoto Tajima Masao Fujimaki 《Bioscience, biotechnology, and biochemistry》2013,77(4):547-552
Reaction rates of the extracts from foods and biological tissues with hydrated electrons were measured by using competition with N2O. Water and 3% Na2S04 aqueous extracts of pork and water extract of onion gave results which conformed to the simple relationship of competition. An addition test of the onion with acetone and nitrate suggested that their reactivities were simply additive, but the additive effect of cysteine was complicated. 相似文献
2.
A sialic acid binding lectin, AchatininH was purified from the hemolymph of Achatina fulica snail. To identify the site of synthesis of AchatininH, in vitro incubation studies in presence of labelled amino acid precursor were performed. Different organs from the snail were sliced and incubated in methionine-deficient Eagle's minimum essential medium containing [35S] - methionine at 25° C for 5 h. After termination of incubation, tissues were homogenized, centrifuged and the de novo synthesized protein was immunoprecipitated with specific AchatininH antibody, followed by protein-A. The precipitated antigen-antibody complex was analysed by SDS-PAGE. Data obtained from native gel electrophoresis and SDS-PAGE radioautographic analysis indicates that AchatininH is synthesized in the albumen gland.Abbreviations SDS-PAGE
Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis
- PRO
2,5 Diphenyl Oxazole
- POPOP
1,4 bis [2-(4-methyl-6-phenyloxazolyl)] Benzene
- TBS
Tris Buffered Saline
- SSM
Sheep Submaxillary Mucin 相似文献
3.
A monosaccharide (β-d-glucose) and polysaccharide (soluble starch) were used as structure directing and subsequently stabilizing agents for the synthesis of spherical nanoparticles (NPs) and nanowires of silver and gold. Homogeneous monodispersed Ag(0) nanoparticles (Ag NPs) of 15 nm diameter were obtained when 10−4 M AgNO3 precursor salt was reduced in starch (1 wt %)–water gel by 1 wt % β-d-glucose. For a second preparation the effect of reducing agents on the synthesis of Au(0) metallic nanoparticles (Au NPs) of 2 × 10−4 M concentration prepared in a β-d-glucose (0.03 M)–water dispersion was studied first in detail. Different equivalent amounts of NaBH4 and a number of pH values were evaluated for the reduction of the Au salt HAuCl4·3H2O to obtain Au NPs. The type and the amount of reducing agent, as well as the pH of the solution was shown to affect the size and morphology of the NPs. NaBH4 (4 equiv) produced the smallest (5.3 nm (σ 0.7)) metallic particles compared to larger particles (10.0 nm (σ 1.4)) when the salt was reduced by 1 equiv of NaBH4. Addition of excess NaBH4 caused the NPs to settle out as a precipitate forming a mesh or wire structure rather than monodispersed particles. Low pH (pH 6) resulted in incomplete reduction, while at pH 8 the salt was completely reduced. When the salt was reduced by NaOH at pH 8, the particles were larger (14.2 nm) and less homogeneous (σ 2.8) compared to those from NaBH4 reduction. 相似文献
4.
《Bioscience, biotechnology, and biochemistry》2013,77(12):2031-2035
Evidence has been reported that bulb development in onion plants (Allium cepa L.) is controlled by endogenous bulbing and anti-bulbing hormones, and that gibberellin (GA) is a candidate for anti-bulbing hormone (ABH). In this study, we identified a series of C-13-H GAs (GA12, GA15, GA24, GA9, GA4, GA34, and 3-epi-GA4) and a series of C-13-OH GAs (GA44, GA20, GA1 and GA8) from the leaf sheaths including the lower part of leaf blades of onion plants (cv. Senshu-Chuko). These results suggested that two independent GA biosynthetic pathways, the early-non-hydroxylation pathway to GA4 (active GA) and early-13-hydroxylation pathway to GA1 (active GA), exist in onion plants. It was also suggested that GA4 and GA1 have almost the same ability to inhibit bulb development in onion plants induced by treatment with an inhibitor of GA biosynthesis, uniconazole-P. The endogenous levels of GA1 and GA4, and their direct precursors, GA20 and GA9, in leaf blades, leaf sheaths, and roots of 4-week-old bulbing and non-bulbing onion plants were measured by gas chromatography/selected ion monitoring with the corresponding [2H]labeled GAs as internal standards. In most cases, the GA levels in long-day (LD)-grown bulbing onion plants were higher than those of short-day (SD)-grown non-bulbing onion plants, but the GA1 level in leaf blades of SD-grown onion plants was rather higher than that of LD-grown onion plants. Relationship between the endogenous GAs and bulb development in onion plants is discussed. 相似文献
5.
The activity, properties, and developmental pattern of cysteine sulfinate transaminase (CSA-T) were studied in chick retina and compared with the activity, properties, and developmental pattern of glutamate oxaloacetate transaminase (GOT). Their optimum pH is identical whereas the effect of pyridoxal phosphate seems to be different. Developmental patterns are also different. TheK
m
andV
m
of CSA-T and GOT were determined in chick retina homogenate. These results suggest that two different enzymes are responsible for the transamination of cysteine sulfinate (CSA) and aspartate. 相似文献
6.
Lai WC Peach ML Lybrand TP Hazelbauer GL 《Protein science : a publication of the Protein Society》2006,15(1):94-101
Hundreds of bacterial chemoreceptors from many species have periplasmic, ligand‐recognition domains of approximately the same size, but little or no sequence identity. The only structure determined is for the periplasmic domain of chemoreceptor Tar from Salmonella and Escherichia coli. Do sequence‐divergent but similarly sized chemoreceptor periplasmic domains have related structures? We addressed this issue for the periplasmic domain of chemoreceptor TrgE from E. coli, which has a low level of sequence similarity to Tar, by combining homology modeling and diagnostic cross‐linking between pairs of introduced cysteines. A homology model of the TrgE domain was created using the homodimeric, four‐helix bundle structure of the TarS domain from Salmonella. In this model, we chose four pairs of positions at which introduced cysteines would be sufficiently close to form disulfides across each of four different helical interfaces. For each pair we chose a second pair, in which one cysteine of the original pair was shifted by one position around the helix and thus would be less favorably placed for disulfide formation. We created genes coding for proteins containing four such pairs of cysteine pairs and investigated disulfide formation in vivo as well as functional consequences of the substitutions and disulfides between neighboring helices. Results of the experimental tests provided strong support for the accuracy of the model, indicating that the TrgE periplasmic domain is very similar to the TarS domain. Diagnostic cross‐linking of paired pairs of introduced cysteines could be applied generally as a stringent test of homology models. 相似文献
7.
Phytochrome was determined in etiolated laminae of Avena sativaL. either without pretreatment or after 5 min of red irradiation followed by different periods of darkness (0–24 h). At given intervals laminae were homogenized and phytochrome was determined spectrophotometrically in the total homogenate and in purified etioplasts and mitochondria. Enhanced specific activity of phytochrome was found in all fractions after the irradiation in comparison to dark controls. Phytochrome destruction was observed in all fractions at the beginning of the subsequent dark period. Whereas the homogenate and the mitochondrial fraction showed a continuous destruction so that phytochrome reached a level far below that in etiolated plants, the phytochrome level in the plastid fraction reacheda minimum at 2 h with a subsequent increase beyond the dark level. This increase was most pronounced between 4 and 8 h after the red irradiation. The results are discussed in terms of the destruction and possible de novo synthesis of phytochrome that may be different in mitochondria and plastids.Abbreviations Ptot
total phytochrome
- Pr
red absorbing form of phytochrome
- Pfr
far-red absorbing form of phytochrome
- ER
endoplasmic reticulum 相似文献
8.
Liuzhang Ouyang Wei Chen Jiangwen Liu Michael Felderhoff Hui Wang Min Zhu 《Liver Transplantation》2017,7(19)
Sodium borohydride (NaBH4) is regarded as an excellent hydrogen‐generated material, but its irreversibility of hydrolysis and high cost of regeneration restrict its large‐scale application. In this study a convenient and economical method for NaBH4 regeneration is developed for the first time without hydrides used as starting materials for the reduction process. The real hydrolysis by‐products (NaBO2 · 2H2O and NaBO2 · 4H2O), instead of dehydrated sodium metaborate (NaBO2), are applied for the regeneration of NaBH4 with Mg at room temperature and atmospheric pressure. Therefore, the troublesome heat‐wasting process to obtain NaBO2 using a drying procedure at over 350 °C from NaBO2 · xH2O is omitted. Moreover, the highest regeneration yields of NaBH4 are achieved to date with 68.55% and 64.06% from reaction with NaBO2 · 2H2O and NaBO2 · 4H2O, respectively. The cost of NaBH4 regeneration shows a 34‐fold reduction compared to the previous study that uses MgH2 as the reduction agent, where H2 is obtained from a separate process. Furthermore, the regeneration mechanism of NaBH4 is clarified and the intermediate compound, NaBH3(OH), is successfully observed for the first time during the regeneration process. 相似文献
9.
Cross‐strand disulfides bridge two cysteines in a registered pair of antiparallel β‐strands. A nonredundant data set comprising 5025 polypeptides containing 2311 disulfides was used to study cross‐strand disulfides. Seventy‐six cross‐strand disulfides were found of which 75 and 1 occurred at non‐hydrogen‐bonded (NHB) and hydrogen‐bonded (HB) registered pairs, respectively. Conformational analysis and modeling studies demonstrated that disulfide formation at HB pairs necessarily requires an extremely rare and positive χ1 value for at least one of the cysteine residues. Disulfides at HB positions also have more unfavorable steric repulsion with the main chain. Thirteen pairs of disulfides were introduced in NHB and HB pairs in four model proteins: leucine binding protein (LBP), leucine, isoleucine, valine binding protein (LIVBP), maltose binding protein (MBP), and Top7. All mutants LIVBP T247C V331C showed disulfide formation either on purification, or on treatment with oxidants. Protein stability in both oxidized and reduced states of all mutants was measured. Relative to wild type, LBP and MBP mutants were destabilized with respect to chemical denaturation, although the sole exposed NHB LBP mutant showed an increase of 3.1°C in T m . All Top7 mutants were characterized for stability through guanidinium thiocyanate chemical denaturation. Both exposed and two of the three buried NHB mutants were appreciably stabilized. All four HB Top7 mutants were destabilized (ΔΔG 0 = ?3.3 to ?6.7 kcal/mol). The data demonstrate that introduction of cross‐strand disulfides at exposed NHB pairs is a robust method of improving protein stability. All four exposed Top7 disulfide mutants showed mild redox activity. Proteins 2010. © 2010 Wiley‐Liss, Inc. 相似文献
10.
Abstract The first synthesis of nitro-multideoxy-sugar containing nucleosides was achieved. 1-(4,6-O-Benzylidene-3-deoxy-3-nitro-β-D-glucopyranosyl)uracil (3) was converted in 75% yield into 1-(4,6-O-benzylidene-2,3-dideoxy-3-nitro-arabinohexopyranosyl)uracil (7) by acetylation followed by NaBH4 reduction in methanol. De-O-benzylidenation with CF3CO2H afforded crystalline 1-(2,3-dideoxy-3-nitro-β-D-arabinohexopyranosyl)uracil (S) was obtained in 87% yield. Raney Ni reduction of 8 afforded the corresponding 3′-amino-nucleoside 9. Acetylation of 8 followed by NaBH4 treatment afforded an 8:1 mixture from which 1-(2,3,4-trideoxy-3-nitro-β-D-threohexopyranosyl)-uracil (14) was obtained in pure crystalline form. After Raney Ni reduction of the mixture, 1-(3-amino-2,3,4-trideoxy-β-d-threo-hexopyranosyl)uracil (16) and its erythro epimer 21 were isolated. 1-(4,6-O-Benzylidene-2,3-dideoxy-3-nitro-β-d-lyxohexopyranosyl)uracil (24) was prepared in 72% yield from 1-(4,6-O-benzylidene-3-deoxy-3-nitro-β-d-galactopyranosyl)uracil (4) by acetylation and subsequent reduction with NaBH4. De-O-benzylid-enation of 23 afforded 1-(2,3,4-trideoxy-3-nitro-β-d-lyxohexopyranosyl)uracil (25) in 83% yield. Schmidt-Rutz reaction of 25 followed by NaBH4 reduction afforded a mixture of threo and elythro isomers of 2′,3′,4′-trideoxy-3′-nitro-hexopyranosyluracil, from which pure 16 and 21 were obtained. 相似文献
11.
S-glutathionylation, the formation of mixed disulfides of glutathione with cysteine residues of proteins, is a broadly observed
physiological modification that occurs in response to oxidative stress. Since cysteine residues are particularly susceptible
to oxidative modification by reactive oxygen species, S-glutathionylation can protect proteins from irreversible oxidation. In this study, we show that the kinase activity of the
non-receptor tyrosine kinase c-Abl is inhibited by in vitro thiol modification; specifically, the cysteine residues of c-Abl
are modified by S-glutathionylation and by thiol alkylating agents such as 4-acetamido-4′-maleimidylstilbene-2,2′-disulfonic acid and N-ethylmaleimide. Modification of cysteine residues of c-Abl tyrosine kinase using glutathione disulfide and thiol alkylating
agents corresponds to a concomitant loss of kinase activity. We also demonstrate that S-glutathionylation of c-Abl can be reversed using a physiological system involving glutaredoxin and this reversal restores
c-Abl kinase activity. To our knowledge, these are the first data to show S-glutathionylation of c-Abl, and this modification may represent a mechanism of regulation of c-Abl kinase activity in cells
under oxidative stress. 相似文献
12.
Md. Motiar Rohman Md. Daud Hossain Toshisada Suzuki Goro Takada Masayuki Fujita 《Acta Physiologiae Plantarum》2009,31(2):301-309
The onion (Allium
cepa L.) bulb has a high level of glutathione S-transferase (GST) activity, and it is a rich source of sulfur compounds as well as flavonoids. To investigate interactions
between onion bulb GSTs and metabolites, we separated onion bulb GSTs (GSTa and GSTb as minor GSTs and GSTc, GSTd and GSTe
as dominant GSTs) by DEAE-cellulose chromatography. In Western blot analysis with anti-CmGSTF1 antiserum, GSTc and GSTd fractions showed a thick band. A cDNA (AcGSTF1) corresponding to GSTc was immunoscreened with the same antiserum from an onion bulb cDNA library and its bacterial expression product was also
subjected to investigation. Among the sulfur compounds, nonphysiological compounds, S-hexyl glutathione (GSH) and S-butyl GSH, showed strong inhibitory effects on 1-chloro-2,4-dinitrobenezene (CDNB)-conjugating activities of GSTa, GSTb and
GSTe. However, physiological sulfur compounds, S-methyl GSH, S-propyl GSH, S-lactoyl GSH and S-ethyl-l-cysteine sulfoxide, had small or almost no inhibitory effects. Therefore, onion sulfur compounds might have the least possibility
to be substantial inhibitors of onion GSTs. On the other hand, the activities of GSTc, GSTd and AcGSTF1 were strongly inhibited by flavonoids, quercetin, luteolin, apigenin and kaempferol. Ethylacetate (EtOAc) extract of
onion bulb contained quercetin-4′-glucoside as a major inhibitory substance. The strong inhibitory effects of quercetin-4′-glucoside
on GSTc and GSTd as well as on AcGSTF1 (50% inhibitory concentration (IC50): 9.5, 7.5 and 11.2 μM, respectively) along with its high concentration (226 μM) in the onion bulb indicates that quercetin-4′-glucoside
is a physiological inhibitor of dominant GSTs in the onion bulb. 相似文献
13.
《Journal of enzyme inhibition and medicinal chemistry》2013,28(2):290-295
Thioethers are the main flavor compounds found in Liliaceae Allium vegetables and have been shown to have beneficial effects against several diseases correlated with metabolic syndrome. The inhibitory effects of six thioethers on fatty acid synthase (FAS) were investigated. Dose-dependent and time-dependent inhibitions of FAS by one trisulfide and two disulfides were revealed. Diallyl trisulfide (DATS, IC50 = 8.37 μM) was the most active of these thioethers. Inhibition kinetics, substrate protection analysis, and stoichiometric assay revealed that DATS interacted with both essential sulfhydryl groups on the acyl-carrier protein and β-ketoacyl synthase domain of FAS to inactivate the enzyme. The inactivation by DATS represented affinity-labeling kinetics. The active thioethers also inhibited the differentiation and lipid accumulation of 3T3-L1 preadipocytes, and the effect was related to their inhibition of FAS. It is suggested that the inhibition on FAS by thioethers and Allium vegetables is an important factor for their effects against metabolic syndrome. 相似文献
14.
Shosuke Ito Makoto Ojika Toshiharu Yamashita Kazumasa Wakamatsu 《Pigment cell & melanoma research》2014,27(5):744-753
RS‐4‐(4‐Hydroxyphenyl)‐2‐butanol (rhododendrol, RD) was used as a skin‐whitening agent until it was reported to induce leukoderma in July 2013. To explore the mechanism underlying its melanocyte toxicity, we characterized the tyrosinase‐catalyzed oxidation of RD using spectrophotometry and HPLC. Oxidation of RD with mushroom tyrosinase rapidly produced RD‐quinone, which was quickly converted to 2‐methylchromane‐6,7‐dione (RD‐cyclic quinone) and RD‐hydroxy‐p‐quinone through cyclization and addition of water molecule, respectively. RD‐quinone and RD‐cyclic quinone were identified as RD‐catechol and RD‐cyclic catechol after NaBH4 reduction. Autoxidation of RD‐cyclic catechol produced superoxide radical. RD‐quinone and RD‐cyclic quinone quantitatively bound to thiols such as cysteine and GSH. These results suggest that the melanocyte toxicity of RD is caused by its tyrosinase‐catalyzed oxidation through production of RD‐cyclic quinone which depletes cytosolic GSH and then binds to essential cellular proteins through their sulfhydryl groups. The production of ROS through autoxidation of RD‐cyclic catechol may augment the toxicity. 相似文献
15.
Hiroyuki Nishimura Akio Asahi Kazuya Fujiwara Junya Mizutani Yataro Obata 《Bioscience, biotechnology, and biochemistry》2013,77(12):1831-1835
The effect of γ-irradiation on the flavor of Onions (Senshu Yellow) associated with sprout-inhibition has been investigated. The relative amounts of propionaldehyde, n-propyl mercaptan and di-n-propyl disulfide in onions stored for 0, 5, 10, 20 and 30 days, respectively, after irradiation were estimated by measurement of peak areas of gas chromatograms. It was observed that the lachrymatory character and the pungent flavor had been decreased by γ-irradiation (remarkably at 70 and 700 Krads). In this connection, the amounts of propionaldehyde and di-n-propyl disulfide were decreased with increasing radiation dose and storage period at room temperature (20 to 25°C) and at low temperature (4°C). Moreover, it was observed that the sweetness had been decreased by γ-irradiation, but the amount of n-propyl mercaptan was increased with radiation dose and storage period. Therefore it seems that there is no correlation between the sweetness of onion and the amount of n-propyl mercaptan. 相似文献
16.
Jiro Sekiya Tadahiko Kajiwara Akikazu Hatanaka 《Bioscience, biotechnology, and biochemistry》2013,77(5):969-980
1. Etiolated seedlings of alfalfa and cucumber evolved n-hexanal from linoleic acid and cis-3-hexenal and trans-2-hexenal from linolenic acid when they were homogenized.2. The activities for n-hexanal formation from linoleic acid, lipoxygenase and hydro-peroxide lyase were maximum in dry seeds and 1~2 day-old etiolated seedlings of alfalfa, and in 6~7 day-old etiolated seedlings of cucumber.3. n-Hexanal was produced from linoleic acid and 13-hydroperoxylinoleic acid by the crude extracts of etiolated alfalfa and cucumber seedlings. cis-3-Hexenal and trans-2-hexenal were produced from linolenic acid and 13-hydroperoxylinolenic acid by the crude extracts of etiolated alfalfa and cucumber seedlings. But these extracts, particulariy cucumber one, showed a high isomerizing activity from cis-3-hexenal to trans-2-hexenal.4. When the C8-aldehydes were produced from linoleic acid and linolenic acid by the crude extracts, formation of hydroperoxides of these C18-fatty acids was observed.5. When 9-hydroperoxylinoleic acid was used as a substrate, trans-2-nonenal was produced by the cucumber homogenate but not by the alfalfa homogenate.6. As the enzymes concerned with C6-aldehyde formation, lipoxygenase was partially purified from alfalfa and cucumber seedlings and hydroperoxide lyase, from cucumber seedlings. Lipoxygenase was found in a soluble fraction, but hydroperoxide lyase was in a membrane bound form. Alfalfa lipoxygenase catalyzed formation of 9- and 13-hydroperoxylinoleic acid (35: 65) from linoleic acid and cucumber one, mainly 13-hydroperoxylinoleic acid formation. Alfalfa hydroperoxide lyase catalyzed n-hexanal formation from 13-hydroperoxylinoleic acid, but cucumber one catalyzed formation of n-hexanal and trans-2-nonenal from 13- and 9-hydroperoxylinoleic acid, respectively.7. From the above results, the biosynthetic pathway for C6-aldehyde formation in etiolated alfalfa and cucumber seedlings is established that C6-aldehydes (n-hexanal, cis-3-hexenal and trans-2-hexenal) are produced from linoleic acid and linolenic acid via their 13-hydroperoxides by lipoxygenase and hydroperoxide lyase. 相似文献
17.
The decomposition of jellyfish after major bloom events results in the release of large amounts of nutrients, which can significantly
alter nutrient and oxygen dynamics in the surrounding environment. The response of the ambient bacterial community to decomposing
jellyfish biomass was evaluated in two marine ecosystems, the Gulf of Trieste (northern Adriatic Sea) and Big Lake (Mljet
Island, southern Adriatic Sea). The major difference between these two ecosystems is that Aurelia sp. medusae occur throughout the year in the oligotrophic Big Lake, whereas in the mesotrophic Gulf of Trieste, they occur
only seasonally and often as blooms. Addition of homogenized jellyfish to enclosed bottles containing ambient water from each
of these systems triggered considerable changes in the bacterial community dynamics and in the nutrient regime. The high concentrations
of protein, dissolved organic phosphorous (DOP), and PO4
3− immediately after homogenate addition stimulated increase in bacterial abundance and production rate, coupled with NH4
+ accumulation in both ecosystems. Our preliminary results of the bacterial community structure, as determined with denaturing
gradient gel electrophoresis, indicated differences in the bacterial community response between the two ecosystems. Despite
divergence in the bacterial community responses to jellyfish homogenate, increased bacterial biomass and growth rates in both
distinctive marine systems indicate potentially significant effects of decaying jellyfish blooms on microbial plankton. 相似文献
18.
Jolanta Krudysz-Amblo Mark E. Jennings II Tyler Knight Dwight E. Matthews Kenneth G. Mann Saulius Butenas 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013
Background
Tissue factor (TF), an in vivo initiator of blood coagulation, is a transmembrane protein and has two disulfides in the extracellular domain. The integrity of one cysteine pair, Cys186–Cys209, has been hypothesized to be essential for an allosteric “decryption” phenomenon, presumably regulating TF procoagulant function, which has been the subject of a lengthy debate. The conclusions of published studies on this subject are based on indirect evidences obtained by the use of reagents with potentially oxidizing/reducing properties.Methods
The status of disulfides in recombinant TF1–263 and natural placental TF in their non-reduced native and reduced forms was determined by mass-spectrometry. Functional assays were performed to assess TF cofactor function.Results
In native proteins, all four cysteines of the extracellular domain of TF are oxidized. Reduced TF retains factor VIIa binding capacity but completely loses the cofactor function.Conclusion
The reduction of TF disulfides (with or without alkylation) eliminates TF regulation of factor VIIa catalytic function in both membrane dependent FX activation and membrane independent synthetic substrate hydrolysis.General significance
Results of this study advance our knowledge on TF structure/function relationships. 相似文献19.
Jose Sraer Marcelle Bens Jean-Paul Oudinet Raymond Ardaillou 《Prostaglandins & other lipid mediators》1986,31(5)
Since leukotriene C4 (LTC4) may be locally synthesized by bone marrow-derived cells infiltrating the kidney in inflammatory renal diseases we examined the in vitro metabolism of exogenously added |3H| LTC4 by rat glomeruli and papilla using radiometric HPLC. Homogenized as well as intact glomeruli converted |3H| LTC4 mainly into |3h| LTE4 (83%) and, at a smaller extent, into |3H| LTD4 (4%). Intact |3H| LTC4 represented 13% of the sum of radioactive leukotrienes. Addition of L-cysteine resulted in accumulation of LTD4. In contrast, there was nearly no conversion of |3H| LTC4 (87% ntact) in the presence of homogenized papilla. The metabolism of |3H| LTC4 by the glomeruli was time- and temperature- dependent. The 10,000 g supernatant and pellet of homogenized glomeruli both retained the ability to metabolize |3H| LTC4. The papillary 10,000 g supernatant was inactive, as found for the total homogenate, whereas the papillary 10,000 g pellet separated from its supernatant could transform |3H| LTC4 into its metabolites, LTD4 and LTE4. Addition of increasing amounts of papillary 10,000 g supernatant to homogenized glomeruli progressively protected |3H| LTC4 from its bioconversion. These results demonstrate that both glomeruli and papilla possess the γ-glutamyl transpeptidase and dipeptidase necessary to process LTC4. However, the enzyme activity of the papilla is unmasked only when the inhibitor present in the 10,000 g supernatant is separated from the enzyme present in the pellet. 相似文献
20.
Kazufumi Akiyama Henry I. Yamamura Brian C. Wilkes Wayne L. Cody Victor J. Hruby Ana Maria de L. Castrucci Mac E. Hadley 《Peptides》1984,5(6)
α-Melanotropin (α-MSH) retains less than 1% of its original activity after a 60 min incubation with 10% rat brain homogenate. [Nle4, D-Phe7]-α-MSH is nonbiodegradable in rat serum (240 min incubation) and still maintains 10% of its original activity in 10% rat brain homogenate (240 min incubation). The related fragment analogue, Ac-[Nle4, D-Phe7]-α-MSH4–10-NH2, retains 50% of its activity after a 240 min incubation in rat brain homogenate, whereas Ac-[Nle4, D-Phe7]-α-MSH4–11-NH2 is totally resistant to inactivation by rat brain homogenate. Both [Nle4, D-Phe7]-fragments are resistant to degradation by rat serum, but [Nle4]-α-MSH, Ac-[Nle4]-α-MSH4–10-NH2 and Ac-[Nle4]-α-MSH4–11-NH2 are rapidly inactivated under both conditions. The cyclic melanotropin, [
]-α-MSH, is inactivated in rat brain homogenate as is the shorter Ac-[
]-α-MSH4–10-NH2 analogue, but neither cyclic melanotropin is inactivated upon incubation in serum from rats. Ac-[
]-α-MSH4–10-NH2 is resistant to inactivation by either rat serum or a brain homogenate. Some of these melanotropin analogues may provide useful probes for the localization and characterization of putative melanotropin receptors in both the central nervous system and peripheral tissues. 相似文献