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1.
Isotope effects associated with the anaerobic oxidation of sulfide by the purple photosynthetic bacterium, Chromatium vinosum 总被引:2,自引:0,他引:2
Abstract Small inverse isotope effects of 1–3‰ were consistently observed for the oxidation of sulfide to elemental sulfur during anaerobic photometabolism by Chromatium vinosum . The inverse fractionation can be accounted for by an equilibrium isotope effect between H2 S and HS− , and may indicate that C. vinosum (and other photosynthetic bacteria) utilizes H2 S rather than HS− as the substrate during sulfide oxidation. 相似文献
2.
The effect of short-term H2 S fumigation on water-soluble sulphydryl and glutathione levels in spinach 总被引:2,自引:0,他引:2
Abstract. Short-term fumigation of Spinacia oleracea with 380 μg m−3 H2 S (250 ppb) resulted in a rapid accumulation of water-soluble SH-compounds in the shoots. After 1 h exposure a substantial increase in the SH-content was already detectable and maximal accumulation, three- to four-fold that in control plants, was observed after 24 h of exposure. Irradiation during H2 S exposure only slightly affected the rate and level of SH-accumulation. H2 S fumigation did not affect the water-soluble SH-content of the roots. Glutathione was the sole water-soluble SH-compound accumulating upon exposure to H2 S. It was calculated that during the first hour of exposure to 380 μg m−3 H2 S 39% of the possible absorbed H2 S was converted into glutathione. The SH-content of the water-soluble proteins of the shoots was not affected by H2 S exposure. When fumigation was stopped, a rapid decrease in glutathione content was observed and after 48 h the content was comparable to that of the control plants. Contrary to H2 S, SO2 fumigation did not result in a rapid accumulation of glutathione in spinach shoots. The possible role of glutathione accumulation during H2 S fumigation is discussed. 相似文献
3.
Spirochaeta smaragdinae sp. nov., a new mesophilic strictly anaerobic spirochete from an oil field 总被引:1,自引:0,他引:1
Michel Magot Marie-Laure Fardeau Odile Arnauld Colette Lanau Bernard Ollivier P. Thomas B.K.C. Patel 《FEMS microbiology letters》1997,155(2):185-191
An obligately anaerobic spirochete designated strain SEBR 4228T (T = type strain) was isolated from an oil field of Congo, Central Africa. The strain grew optimally with a sodium chloride concentration of 5% (sodium chloride concentration growth range 1.0–10%) at 37°C (growth temperature range 20–40°C) and pH of 7.0–7.2 (pH growth range pH 5.5–8.0). Strain SEBR 4228T grew on carbohydrates (glucose, fructose, ribose, d -xylose, galactose, mannitol and mannose), glycerol, fumarate, peptides and yeast extract. Yeast extract was required for growth and could not be replaced by vitamins. It reduced thiosulfate and sulfur, to H2 S. Glucose was oxidised to lactate, acetate, CO2 and H2 S in the presence of thiosulfate but in its absence lactate, ethanol, CO2 and H2 were produced. Fumarate was fermented to acetate and succinate. The G+C content of strain SEBR 4228T was 50%. Strain SEBR 4228T was spiral shaped measuring 5–30 by 0.3–0.5 μm and was motile with a corkscrew-like motion. Electron microscopy revealed the presence of periplasmic flagella in a 1-2-1 arrangement. Strain SEBR 4228T possessed features typical of the members of the genus Spirochaeta . 16S rRNA sequence analysis revealed that it was closely related to Spirochaeta bajacaliforniensis (similarity 98.6%). The lack of DNA homology with S. bajacaliforniensis (38%), together with other phenotypic differences, indicated that strain SEBR 4228T is a new species, which we have designated Spirochaeta smaragdinae . The type strain is SEBR 4228T (= DSM 11293). 相似文献
4.
SUMMARY: Sterilized raw sewage sludge enriched with sulphate and inoculated with pure strains of Desulphovibrio desulphuricans produced negligible sulphide. Unsterilized sludge supplemented with 7% (w/v) CaSO4 .2H2 O and inoculated with crude cultures of sulphate-reducing bacteria obtained from sewage yielded 1·0% S2- (wt S2- produced as H2 S/vol. of raw sludge) in 6 months at 30°. By repeated subculture more active cultures developed which produced 1% S2- in 7 days and 1·2–1·9% in 28 days. Digested sludge yielded only 0·1% S2- . In semicontinuous fermentations at 30°, raw sludge without added sulphate produced 20 times its own volume of gas containing 70% CH4 and 30% CO2 . When 5% CaSO4 .2H2 O and an active crude culture of sulphate reducers were added, gas production decreased steadily to zero. There were no differences in pH, temperature and redox potential in sludges producing methane or sulphide. The chief cause of inhibition appeared to be the action of sulphide: 0·02% soluble sulphide (S2- ) totally inhibited methane formation; 0·01% S2- initially decreased gas production by one-quarter but there was a slow recovery to normal, suggesting acclimatization of the methane-producing organisms to sulphide.
Linked fermentations, in which gas from a methane fermentation swept H2 S from a sulphide fermentation, gave a final gas mixture of about 60% CH4 , 30% CO2 and 5–10% H2 S. The yield of sulphide depended on the rate of sweeping. 相似文献
Linked fermentations, in which gas from a methane fermentation swept H
5.
Valentino Casolo Enrico Braidot Elisa Chiandussi Angelo Vianello Francesco Macrì 《Physiologia plantarum》2003,118(3):313-318
The role of a recently identified K+ ATP channel in preventing H2 O2 formation was examined in isolated pea stem mitochondria. The succinate-dependent H2 O2 formation was progressively inhibited, when mitochondria were resuspended in media containing increasing concentration of KCl (from 0.05 to 0.15 M ). This inhibition was linked to a partial dissipation of the transmembrane electrical potential (ΔΨ) induced by KCl. Conversely, the malate plus glutamate-dependent H2 O2 formation was not influenced. The succinate-sustained H2 O2 generation was also unaffected by nigericin (a H+ /K+ exchanger), but completely prevented by valinomycin (a K+ ionophore). In addition, cyclosporin A (a K+ ATP channel opener) inhibited this H2 O2 formation, while ATP (an inhibitor of the channel opening) slightly increased it. The inhibitory effect of ATP was strongly stimulated in the presence of atractylate (an inhibitor of the adenine nucleotide translocase), thus suggesting that the receptor for ATP on the K+ channel faces the intermembrane space. Finally, the succinate-dependent H2 O2 formation was partially prevented by phenylarsine oxide (a thiol oxidant). 相似文献
6.
When illuminated leaf discs and detached leaves of spinach ( Spinacia oleracea L. cv. Estivato) were exposed to 0.4 and 0.25 μl 1-1 H2 S, respectively, pool sizes of cysteine and glutathione increased. In the dark, apart from these compounds, the level of γ-glutamyl-cysteine also increased. Incubation of leaf discs with 1.0 m M buthionine sulfoximine (BSO) resulted in the accumulation of cysteine only, both in the light and in darkness. When glycine was supplied to the petioles of detached leaves exposed to H2 S in the dark, the accumulation of glutathione was stimulated, while γ-glutamyl-cysteine accumulation was prevented completely. Glycolate and glyoxylate, precursors of glycine in the glycolate pathway, had nearly the same effect as glycine. Although other amino acids were apparently taken up equally well as glycine when supplied to the petiole, they were much less effective, or not effective at all, in restoring glutathione synthesis in the dark. These results provide evidence, that H2 S-induced glutathione accumulation in spinach leaves in the dark is limited by the availability of glycine, giving rise to the accumulation of the metabolic precursor γ-glutamyl-cysteine. 相似文献
7.
Hydrogen sulfide (H2 S) is a well known and pungent toxic gas that has recently been shown to be synthesised in man from the amino acids cystathionine, homocysteine and cysteine by at least two distinct enzymes; cystathionine-γ-lyase and cystathionine-β-synthase. In the past few years, H2 S has emerged as a novel and increasingly important mediator in the cardiovascular system but delineating the precise physiology and pathophysiology of H2 S is proving to be complex and difficult to unravel with disparate findings reported with cell types, tissue types and animal species reported. Therefore, in this review we summarize the mechanisms by which H2 S has been proposed to regulate blood pressure and cardiac function, discuss the mechanistic discrepancies reported in the literature as well as the therapeutic potential of H2 S. We also examine the methods of H2 S detection in biological fluids, processes for H2 S removal and discuss the reported blood levels of H2 S in man and animal models of cardiovascular pathology. We also highlight the complex interaction of H2 S with nitric oxide in regulating cardiovascular function in health and disease. 相似文献
8.
Effects of 1-Methyl-4-Phenylpyridinium on Isolated Rat Brain Mitochondria: Evidence for a Primary Involvement of Energy Depletion 总被引:7,自引:1,他引:6
T. E. Bates S. J. R. Heales S. E. C. Davies P. Boakye J. B. Clark 《Journal of neurochemistry》1994,63(2):640-648
Abstract: The effects of 1-methyl-4-phenylpyridinium (MPP+ ) on the oxygen consumption, ATP production, H2 O2 production, and mitochondrial NADH-CoQ1 reductase (complex I) activity of isolated rat brain mitochondria were investigated. Using glutamate and malate as substrates, concentrations of 10–100 µ M MPP+ had no effect on state 4 (−ADP) respiration but decreased state 3 (+ADP) respiration and ATP production. Incubating mitochondria with ADP for 30 min after loading with varying concentrations of MPP+ produced a concentration-dependent decrease in H2 O2 production. Incubation of mitochondria with ADP for 60 min after loading with 100 µ M MPP+ caused no loss of complex I activity after washing of MPP+ from the mitochondrial membranes. These data are consistent with MPP+ initially binding specifically to complex I and inhibiting both the flow of reducing equivalents and the production of H2 O2 by the mitochondrial respiratory chain, without irreversibly damaging complex I. However, mitochondria incubated with H2 O2 in the presence of Cu2+ ions showed decreased complex I activity. This study provides additional evidence that cellular damage initiated by MPP+ is due primarily to energy depletion caused by specific binding to complex I, any increased damage due to free radical production by mitochondria being a secondary effect. 相似文献
9.
Keita Nagasawa Takeshi Tarui Shigeru Yoshida† Fumiko Sekiguchi Maho Matsunami Ai Ohi Kazuki Fukami Seiji Ichida‡ Hiroyuki Nishikawa§ Atsufumi Kawabata 《Journal of neurochemistry》2009,108(3):676-684
We investigated if stimulation of T-type Ca2+ channels with sodium hydrosulfide (NaHS), a donor of hydrogen sulfide (H2 S), could cause neuronal differentiation of NG108-15 cells. Like dibutyryl cyclic AMP (db-cAMP), treatment with NaHS at 1.5–13.5 mM for 16 h enhanced neurite outgrowth in a concentration-dependent manner. Synergistic neuritogenic effect was obtained in the cells stimulated with NaHS in combination with db-cAMP at subeffective concentrations. Exposure to NaHS or db-cAMP for 2 days resulted in enhancement of expression of high-voltage-activated currents consisting of N-, P/Q-, L- and also other types, but not of T-type currents. Mibefradil, a pan-T-type channel blocker, abolished the neuritogenesis induced by NaHS, but not by db-cAMP. The NaHS-evoked neuritogenesis was also completely blocked by pretreatment with BAPTA/AM, a chelator of intracellular Ca2+ , and by zinc chloride at a concentration known to selectively inhibit Cav 3.2 isoform of T-type Ca2+ channels, but not Cav 3.1 or Cav 3.3. Further, l -ascorbate, recently proven to selectively inhibit Cav 3.2, abolished the neuritogenic effect of NaHS, but not db-cAMP. Our data thus demonstrate that NaHS/H2 S is a novel inducer of neuronal differentiation in NG108-15 cells, as characterized by neuritogenesis and expression of high-voltage-activated currents, and suggest the involvement of T-type Ca2+ channels, especially Cav 3.2. 相似文献
10.
Abstract: We studied the action of H2 O2 on the exocytosis of glutamate by cerebrocortical synaptosomes. The treatment of synaptosomes with H2 O2 (50–150 µ M ) for a few minutes results in a long-lasting depression of the Ca2+ -dependent exocytosis of glutamate, induced by KCl or by the K+ -channel inhibitor 4-aminopyridine. The energy state of synaptosomes, as judged by the level of phosphocreatine and the ATP/ADP ratio, was not affected by H2 O2 , although a transient decrease was observed after the treatment. H2 O2 did not promote peroxidation, as judged by the formation of malondialdehyde. In indo-1-loaded synaptosomes, the treatment with H2 O2 did not modify significantly the KCl-induced increase of [Ca2+ ]i . H2 O2 inhibited exocytosis also when the latter was induced by increasing [Ca2+ ]i with the Ca2+ ionophore ionomycin. The effects of H2 O2 were unchanged in the presence of superoxide dismutase and the presence of the Fe3+ chelator deferoxamine. These results appear to indicate that H2 O2 , apparently without damaging the synaptosomes, induces a long-lasting inhibition of the exocytosis of glutamate by acting directly on the exocytotic process. 相似文献
11.
In the light, glutathione was the major water-soluble, non-protein, sulfhydryl compound in leaves of spinach ( Spinacia oleracea L. cv. Estivato). In the dark, another sulfhydryl compound accumulated, which proved to be γ-glutamyl-cysteine. In the light, exposure of leaves to excess sulfur in the form of atmospheric H2 S (0.25 μl l−1 ) resulted in considerably increased levels of glutathione and cysteine. In the dark, in addition to these thiols, levels of γ-glutamyl-cysteine were also enhanced considerably. When leaves of plants exposed to H2 S in the dark were illuminated, the dipeptide rapidly disappeared. At the same time, glutathione contents increased by approximately the same amount, indicating a light-dependent conversion of γ-glutamyl-cysteine into glutathione. Possible mechanisms for these light-induced changes in thiol metabolism are discussed. 相似文献
12.
Plant responses to H2 S and SO2 fumigation. II. Differences in metabolism of H2 S and SO2 in spinach 总被引:1,自引:0,他引:1
Frank M. Maas Luit J. de Kok Willy Strik-Timmer Pieter J. C. Kuiper 《Physiologia plantarum》1987,70(4):722-728
Fumigation of spinach (Spinacia oleracea L. cvs Estivato and Monosa) with H2 S or SO, for 1 to 6 days resulted in accumulation of sulfhydryl (SH) compounds in the shoots of both H2 S- and SO2 -exposed plants. The sulfate concentration in shoots of SO2 -exposed plants increased linearly with time. SH accumulation showed saturation kinetics as a function of time as well as H2 S concentration, ascribed to the internal H2 S concentration in the plant and the availability of substrates for glutathione synthesis, respectively. SH compounds accumulated more at lower exposure temperatures, whereas sulfate accumulation was more pronounced at higher temperatures. These results are discussed in relation to the possible foliar uptake of H2 S and SO2 , the temperature dependence of uptake and the water solubility of these gases. The possibility of SO2 -induced H2 S emission rather than sulfate accumulation as a source for SH accumulation is also discussed. Cessation of fumigation resulted in a decrease in SH compounds and sulfate content that could be accounted for by sulfur metabolism and growth, respectively. 相似文献
13.
Abstract Bradyrhizobium japonicum and Shewanella putrefaciens were unable to oxidize hydrogen at atmospheric concentrations (0.55 ppmv), neither in suspension nor when added to sterile soil. The K m -value of S. putrefaciens for H2 (39 ppmv in gas phase, 0.22 μM in aqueous phase), using Fe(III) as electron acceptor, showed a 4–5-fold higher affinity for H2 than that of B. japonicum (1200 ppmv; 0.84 μM) or other hydrogen-oxidizing bacteria. However, the V max (4.54 fmol H2 h−1 cell −1 ) and threshold (> 0.5 ppmv; 0.35 nM) of S. putrefaciens and the V max (7.19 fmol H2 h−1 cell−1 ) and threshold (> 0.5 ppmv; 0.35 nM) of B. japonicum were in the same order of magnitude as data for Knallgas bacteria from relevant literature. To enable hydrogen oxidation in soil the soil-samples with S. putrefaciens even had to be supplemented with Fe(III). Fresh soil, on the other hand, oxidized hydrogen very efficiently below atmospheric mixing ratios, demonstrating that there must be other oxidation activities in soil. 相似文献
14.
Antonio G. Cordente Anthony Heinrich Isak S. Pretorius & Jan H. Swiegers 《FEMS yeast research》2009,9(3):446-459
The production of hydrogen sulfide (H2 S) during fermentation is a common and significant problem in the global wine industry as it imparts undesirable off-flavors at low concentrations. The yeast Saccharomyces cerevisiae plays a crucial role in the production of volatile sulfur compounds in wine. In this respect, H2 S is a necessary intermediate in the assimilation of sulfur by yeast through the sulfate reduction sequence with the key enzyme being sulfite reductase. In this study, we used a classical mutagenesis method to develop and isolate a series of strains, derived from a commercial diploid wine yeast (PDM), which showed a drastic reduction in H2 S production in both synthetic and grape juice fermentations. Specific mutations in the MET10 and MET5 genes, which encode the catalytic α- and β-subunits of the sulfite reductase enzyme, respectively, were identified in six of the isolated strains. Fermentations with these strains indicated that, in comparison with the parent strain, H2 S production was reduced by 50–99%, depending on the strain. Further analysis of the wines made with the selected strains indicated that basic chemical parameters were similar to the parent strain except for total sulfite production, which was much higher in some of the mutant strains. 相似文献
15.
Suspension-cultured rose ( Rosa damascena Mill. cv. Gloire de Guilan) cells irradiated with UV-C (254 nm. 558 J m−2 ) showed a transient production of H2 O2 as measured by chemiluminescence of luminol in the presence of peroxidase (EC 1.1 1.1.7). The peak concentration of H2 O2 , which occurred at about 60–90 min after irradiation, was 8–9 μ M . The time course for the appearance of H2 O2 matched that for UV–induced K+ efflux. Treatments that inhibited the UV-induced efflux of K+ , including heat and overnight incubation with cycloheximide and diethylmaleate, also inhibited the appearance of H2 O2 . The converse was not always true, since catalase (EC 1.11.1.6. and salicylhydroxamic acid, which inhibited luminescence, did not stop K+ efflux. We conclude that H2 O2 synthesis depends on K+ efflux. Because H2 .O2 in the extracellular space is required for lignin synthesis in many plant tissues, we suggest that the UV–stimulated production of H2 O2 is an integral part of a defensive lignin synthesis. 相似文献
16.
P. MALLE M. VALLE P. EB R. TAILLIEZ 《Journal of Rapid Methods and Automation in Microbiology》1998,6(2):129-141
H2 S bacteria of seafish flesh are weakly halophilic and require on average 1.68% NaCl according to statistical studies. Enumeration is optimal on PCA-H2 S(a PCA medium supplemented with sulfur sources and increased NaCl concentrations) incubated at 25C. Total aerobic bacteria can be counted simultaneously on this medium. The proportion of H2 S bacteria relative to total aerobic bacteria increased slightly during prolonged storage of the fish, but was highly variable. Models relating H2 S bacterial counts to spoilage of fish are sigmoidal and showed that when the count exceeds 10,000 CFU/g, whole or filleted fish stored in ice at 0C are unfit for consumption. Shewanella putrefaciens accounted for 69% of the H2 S bacteria at the fifth day of storage and 100% at the fifteenth. 相似文献
17.
Sulfide-induced dissimilatory nitrate reduction to ammonia in anaerobic freshwater sediments 总被引:12,自引:0,他引:12
Abstract: Different reduced sulfur compounds (H2 S, FeS, S2 O3 2− ) were tested as electron donors for dissimilatory nitrate reduction in nitrate-amended sediment slurries. Only in the free sulfide-enriched slurries was nitrate appreciably reduced to ammonia ( ), with concomitant oxidation of sulfide to S0 ( ). The initial concentration of free sulfide appears as a factor determining the type of nitrate reduction. At extremely low concentrations of free S2− (metal sulfides) nitrate was reduced via denitrification whereas at higher S2− concentrations, dissimilatory nitrate reduction to ammonia (DNRA) and incomplete denitrification to gaseous nitrogen oxides took place. Sulfide inhibition of NO- and N2 O- reductases is proposed as being responsible for the driving part of the electron flow from S2− to NH4 + . 相似文献
18.
Zhiyuan Zhang Russell E. Rydel Gary J. Drzewiecki Kimberly Fuson Sarah Wright Mark Wogulis James E. Audia Patrick C. May Paul A. Hyslop 《Journal of neurochemistry》1996,67(4):1595-1606
Abstract: H2 O2 and free radical-mediated oxidative stresses have been implicated in mediating amyloid β(1–40) [Aβ(1–40)] neurotoxicity to cultured neurons. In this study, we confirm that addition of the H2 O2 -scavenging enzyme catalase protects neurons in culture against Aβ-mediated toxicity; however, it does so by a mechanism that does not involve its ability to scavenge H2 O2 . Aβ-mediated elevation in intracellular H2 O2 production is suppressed by addition of a potent H2 O2 scavenger without any significant neuroprotection. Three intracellular biochemical markers of H2 O2 -mediated oxidative stress were unchanged by Aβ treatment: (a) glyceraldehyde-3-phosphate dehydrogenase activity, (b) hexose monophosphate shunt activity, and (c) glucose oxidation via the tricarboxylic acid cycle. Ionspray mass spectra of Aβ in the incubation medium indicated that Aβ itself is an unlikely source of reactive oxygen species. In this study we demonstrate that intracellular ATP concentration is compromised during the first 24-h exposure of neurons to Aβ. Our results challenge a pivotal role for H2 O2 generation in mediating Aβ toxicity, and we suggest that impairment of energy homeostasis may be a more significant early factor in the neurodegenerative process. 相似文献
19.
Enzyme activities of assimilatory sulfate reduction were measured in leaves of Pisum sativum L., cv. Vatters Frühbusch, during their ontogenetic development, and during treatment with H2 S and cyst(e)ine. Ribulose bisphosphate (RuBP) carboxylase (EC 4.1.1.39) and ferredoxin-dependent nitrite reductase (Fd-NiR, EC 1.7.7.1) were measured for comparison. In etiolated pea leaves, ATP-sulfurylase (ATPase, EC 2.7.7.4), adenosine 5'-phosphosulfate sulfotransferase (APSSTase), ferredoxin-dependent sulfite reductase (Fd-SiR, EC 1.8.7.1) and O-acetyl-L-serine sulfhydrylase (OASSase, EC 4.2.99.8) activities were measured in appreciable rates, while neither RuBP carboxylase nor Fd-NiR activities could be detected.
During the first 2–7 days after transfer into the light all enzyme activities increased. After reaching maximal activities, ATPase, APSSTase, and Fd-SiR activities decreased in all leaves to low or indetectable levels during the following 3–6 days. RuBP carboxylase, Fd-NiR and OASSase, on the other hand, decreased slowly and were still at high levels of activity at the end of the experiment.
Fumigation of pea plants with 1.5 μl l−1 H2 S delayed the initial increase and the subsequent decrease of ATPase activity by 1–3 days. APSSTase activity decreased for 1–2 days, increased rapidly during the next 4–6 days and retained a high level of activity until the end of the experiment as did Fd-SiR. One to two days after the beginning of fumigation the leaves started to accumulate high amounts of cyst(e)ine.
When pea plants with excised roots were placed on a nutrient solution containing cyst(e)ine, APSSTase activity decreased more on 0.2 and 0.5 m M than on 1.0 m M. Fd-SiR activity was only slightly decreased on 1.0 m M cyst(e)ine. Neither Fd-NiR nor RuBP carboxylase activities were affected. 相似文献
During the first 2–7 days after transfer into the light all enzyme activities increased. After reaching maximal activities, ATPase, APSSTase, and Fd-SiR activities decreased in all leaves to low or indetectable levels during the following 3–6 days. RuBP carboxylase, Fd-NiR and OASSase, on the other hand, decreased slowly and were still at high levels of activity at the end of the experiment.
Fumigation of pea plants with 1.5 μl l
When pea plants with excised roots were placed on a nutrient solution containing cyst(e)ine, APSSTase activity decreased more on 0.2 and 0.5 m M than on 1.0 m M. Fd-SiR activity was only slightly decreased on 1.0 m M cyst(e)ine. Neither Fd-NiR nor RuBP carboxylase activities were affected. 相似文献
20.
Stephen J. Bunn Alistair T. R. Sim Lynn M. Herd Leone M. Austin Peter R. Dunkley 《Journal of neurochemistry》1995,64(3):1370-1378
Abstract: Tyrosine hydroxylase (TOH), the rate-limiting enzyme in catecholamine biosynthesis, is regulated by phosphorylation. Activation of histaminergic H1 receptors on cultured bovine adrenal chromaffin cells stimulated a rapid increase in TOH phosphorylation (within 5 s) that was sustained for at least 5 min. The initial increase in TOH phosphorylation (up to 1 min) was essentially unchanged by the removal of extracellular Ca2+ . In contrast, the H1 -mediated response was abolished by preloading the cells with BAPTA acetoxymethyl ester (50 µ M ) and significantly reduced by prior exposure to caffeine (10 m M for 10 min) to deplete intracellular Ca2+ . Trypticphosphopeptide analysis by HPLC revealed that the H1 response in the presence or absence of extracellular Ca2+ resulted in a major increase in the phosphorylation of Ser19 with smaller increases in that of Ser40 and Ser31 . In contrast, although a brief stimulation with nicotine (30 µ M for 60 s) also resulted in a major increase in Ser19 phosphorylation, this response was abolished in the absence of extracellular Ca2+ . These data indicate that the mobilization of intracellular Ca2+ plays a crucial role in supporting H1 -mediated TOH phosphorylation and may thus have a potentially important role in regulating catecholamine synthesis. 相似文献