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1.
Rhodopseudomonas acidophila strain 7050 can satisfy all its nitrogen and carbon requirements from l-alanine. Addition of 100 M methionine sulfoximine to alanine grown cultures had no effect on growth rate indicating that deamination of alanine via alanine dehydrogenase and re-assimilation of the released NH
4
+
by glutamine synthetase/glutamate synthase was an insignificant route of nitrogen transfer in this bacterium. Determination of aminotransferase activities in cell-free extracts failed to demonstrate the presence of direct routes from alanine to either aspartate or glutamate. The only active aminotransferase involving l-alanine was the alanine-glyoxylate enzyme (114–167 nmol·min–1·mg–1 protein) which produced glycine as end-product. The amino group of glycine was further transaminated to yield aspartate via a glycineoxaloacetate aminotransferase (117–136 nmol·min–1 ·mg–1 protein). No activity was observed when 2-oxoglutarate was substituted for oxaloacetate. The formation of glutamate from aspartate was catalysed by aspartate-2-oxoglutarate aminotransferase (85–107 nmol·min–1·mg–1 protein). Determinations of free intracellular amino acid pools in alanine and alanine+100 M methionine sulfoximine grown cells showed the predominance of glutamate, glycine and aspartate, providing further evidence that in alanine grown cultures R. acidophila satisfies its nitrogen requirements for balanced growth by transamination.Abbreviations ADH
alanine dehydrogenase
- GDH
glutamate dehydrogenase
- GS
glutamine synthetase
- GOGAT
glutamate synthase
- MSO
methionine sulfoximine
- GOT
glutamate-oxaloacetate aminotransferase
- GPT
glutamate-pyruvate amino-transferase
- AGAT
alanine-glyoxylate aminotransferase
- GOAT
glycine-oxaloacetate aminotransferase
- GOTAT
glycine-2-oxoglutarate aminotransferase
- AOAT
alanine-oxaloacetate aminotransferase 相似文献
2.
In a previous paper, and opiate receptors were shown to be co-localized on the same cell in enriched primary cultures of astroglia from neonatal rat cerebral cortex. Activation of the receptors inhibited adenylate cyclase. In this work, the presence of opiate receptors was investigated in astroglial primary cultures from neonatal rat striatum and brain stem. Cyclic adenosine 3, 5-monophosphate accumulation was quantified in the presence of different opioid receptor ligands after stimulation of the cyclic adenosine 3,5-monophosphate system with forskolin. Morphine was used as a receptor agonist. [d-Ala2, D-Leu5]-enkephalin or[d-Pen2,d-Pen5]-enkephalin were used as receptor agonists and dynorphin 1–13 or U-50,488H were used as receptor agonists. Specific antagonists for the respective receptors were used. After striatum or brain stem cultures had been incubated in 10–9–10–5M of each [d-Ala2,d-Leu5]-enkephalin, [d-Pen2, D-Pen5]-enkephalin and Dynorphin 1–13 or U-50,488H, dose related inhibitions of the 10–5M rorskolin stimulated cyclic adenosine 3,5-monophosphate accumulation were observed. The changes were reversed to the forskolin-induced control level in the presence of the respective antagonists. 10–9–10–5M morphine did not significantly change the forskolin-induced accumulation of cyclic adenosine 3,5-monophosphate in the cultures studied. Furthermore, cultures from cerebral cortex, striatum or brain stem were incubated with isoproterenol alone or together with morphine or [d-Ala2,d-Leu5]-enkephalin. Isoproterenol stimulated cyclic adenosine 3,5-monophosphate accumulation more prominently in the cerebral cortex and striatum cultures than in the brain stem cultures. Morphine did not influence isoproterenol-induced cyclic adenosine 3,5-monophosphate accumulation, while [d-Ala2,d-Leu5]-enkephalin inhibited the accumulation. The results indicate that astroglial cells in primary cultures from striatum, brain stem and cerebral cortex express andk opioid receptors linked to the adenylate cyclase/cyclic adenosine 3,5-monophosphate system. No receptors were detected, however, in the present model. Aspects of the relation between the expression of opioid peptides and opioid receptors are discussed, while speculations are also made on the functional aspects of opioid receptors on astroglia. 相似文献
3.
W. P. Low W. T. Ong Y. K. Ip 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,165(7):558-564
Free D- and L-alanine contents were comparable in the body wall and introvert cum retractor muscles of Phascolosoma arcuatum. In contrast, the content of free D-alanine in the internal organs was twice that of free L-alanine. Since alanine aminotrans-ferase from P. arcuatum was L-alanine specific, D-alanine appeared to be synthesized from L-alanine through the action of alanine racemase. Alanine racemase activity was higher in the D-alanine-forming direction in the three body parts of P. arcuatum. In addition, the ratio of DL/LD racemase activity in the internal organs was the lowest among the body parts studied. These results indicate that free D-alanine might be of lesser importance than the free D-isomer to the internal organs as compared to the body wall and introvert cum retractor muscles. Indeed, L-alanine inhibited pyruvate kinase from the body wall and introvert cum retractor muscles but had no effect on the pyruvate kinase from the internal organs. Furthermore, the activity of alanopine dehydrogenase present in the internal organs was significantly lower than those of the body wall and introvert cum retractor muscles. L-Alanine was an essential substrate for alanopine formation in the body wall and introvert cum retractor muscles during hypoxia since alanopine dehydrogenases from these body parts were L-alanine specific. When P. arcuatum was confronted with hypo-osmotic stress, the free D-alanine/total free alanine ratio in the internal organs increased approximately from 0.6 to 0.8 as the total free alanine content decreased. In comparison, those ratios in the body wall and introvert cum retractor muscles remained relatively constant. It was concluded that D- and D-alanine had different physiological functions in the three body parts of P. arcuatum.Abbreviations
ADP
adenosine-5-diphosphate
-
ADH
alanopine dehydrogenase
-
ALT
alanine aminotransferase
-
AOD
amino acid oxidase
-
BW
body wall
-
EDTA
ethylenediaminetetra-acetic acid
-
EGT A
ethylene glyco-bis (-aminoethyl ether)
-
N,N,N,N
tetra-acetic acid
-
ICRM
introvert cum retractor muscles
-
IO
internal organs
-
I
50
inhibitor concentration producing 50% inhibition of enzyme activity
- -KG
-ketoglutarate
-
LDH
lactate dehydrogenase
-
NAD
nicotinamide adenine dinucleotide
-
NADH
nicotinamide adenine dinucleotide (reduced form)
-
PEP
phosphoenolpy-ruvate
-
PEPCK
phosphoenolpyruvate carboxykinase
-
PK
pyruvate kinase
-
PMSF
phenylmethylsulphonyl fluoride
-
SE
standard error
-
SW
sea water
-
TCA
trichloroacetic acid 相似文献
4.
Evoked release of glutamate and aspartate from cultured cerebellar granule cells was studied after preincubation of the cells in tissue culture medium with glucose (6.5 mM), glutamine (1.0 mM),d[3H] aspartate and in some cases aminooxyacetate (5.0 mM) or phenylsuccinate (5.0 mM). The release of endogenous amino acids and ofd-[3H] aspartate was measured under physiological and depolarizing (56 mM KCl) conditions both in the presence and absence of calcium (1.0 mM), glutamine (1.0 mM), aminooxyacetate (5.0 mM) and phenylsuccinate (5.0 mM). The cellular content of glutamate and aspartate was also determined. Of the endogenous amino acids only glutamate was released in a transmitter fashion and newly synthesized glutamate was released preferentially to exogenously suppliedd-[3H] aspartate, a marker for exogenous glutamate. Evoked release of endogenous glutamate was reduced or completely abolished by respectively, aminooxyacetate and phenylsuccinate. In contrast, the release ofd-[3H] aspartate was increased reflecting an unaffected release of exogenous glutamate and an increased psuedospecific radioactivity of the glutamate transmitter pool. Since aminooxyacetate and phenylsuccinate inhibit respectively aspartate aminotransferase and mitochondrial keto-dicarboxylic acid transport it is concluded that replenishment of the glutamate transmitter pool from glutamine, formed in the mitochondrial compartment by the action of glutaminase requires the simultaneous operation of mitochondrial keto-dicarboxylic acid transport and aspartate aminotransferase which is localized both intra- and extra-mitochondrially. The purpose of the latter enzyme apparently is to catalyze both intra- and extra-mitochondrial transamination of -ketoglutarate which is formed intramitochondrially from the glutamate carbon skeleton and transferred across the mitochondrial membrane to the cytosol where transmitter glutamate is formed. This cytoplasmic origin of transmitter glutamate is in aggreement with the finding thatd-[3H] aspartate readily labels the transmitter pool even when synthesis of endogenous transmitter is impaired in the presence of AOAA or phenylsuccinate.Special issue dedicated to Dr Elling Kvamme 相似文献
5.
Kathleen Ottina Jane Lopilato T. Hastings Wilson 《The Journal of membrane biology》1980,56(2):169-175
Summary
p-Nitrophenyl--galactoside (-pNPG) was found to be a substrate for the melibiose transport system ofEscherichia coli. This sugar enters induced cells via the carrier and is split by -galactosidase to galactose andp-nitrophenol. In mutant cells lacking the -galactosidase [3H]--pNPG accumulated to concentrations 15 times higher than the external medium. The transport of -pNPG is inhibited by both Na+ and Li+. Na+ (10mm) reduced the Km for -pNPG from 0.45 to 0.18mm and reduced theV
max from 6.7 nmoles/min/mg dry wt to a value of 3.0. 相似文献
6.
Chlorobium limicola was grown on a mineral salts medium with CO2 as the main carbon source supplemented with specifically labeled 14C propionate and the incorporation of 14C into alanine ( intracellular pyruvate), aspartate ( oxaloacetate), and glutamate ( -ketoglutarate) was studied in long term labeling experiments. During growth in presence of propionate 30% of the cell carbon were derived from propionate and 70% from CO2. Propionate was not oxidized to CO2.All three amino acids were found to be labeled. The labeling patterns indicate that propionate was assimilated via propionyl CoA, methylmalonyl CoA and succinyl CoA. When 1-14C propionate was the labeled precursor no radioactivity was found in the carboxyl group(s) of alanine, aspartate and glutamate, excluding the incorporation of propionate into the amino acids via succinate oxidation to fumarate. With 1-14C propionate preferentially aspartate (C-3) and glutamate (C-2) became labeled, with 2-14C propionate alanine (C-3) and glutamate (C-4). These findings indicate that propionate was incorporated into the amino acids via succinyl CoA, -ketoglutarate, isocitrate, and citrate, followed by a si-type cleavage of citrate to oxaloacetate and acetyl CoA (or acetate). Similar experiments with U-14C acetate confirm these conclusions. Thus, all reactions of the proposed reductive tricarboxylic acid cycle could be demonstrated in autotrophically growing cells. 相似文献
7.
Fast atom bombardment tandem mass spectrometry has been used in the characterization of non-, mono-, di- and trisulfated disaccharides from chondriotin sulfate, dermatan sulfate and hyaluronan. The positional isomers of the sulfate group of mono- and disulfated disaccharides were distinguished from each other by both positive- and negative-ion fast atom bombardment tandem mass spectra, which gave sufficient information characteristic of the isomers. The anomeric isomers of nonsulfated disaccharides were characterized by the technique in the positive-ion mode. This fast atom bombardment collision induced dissociation mass spectrometry/mass spectrometry technique was also applied successfully to the characterization of trisulfated disaccharide.Abbreviations FABMS
fast atom bombardment mass spectrometry
- MI
metastable ion
- CID
collision induced dissociation
- MIKE
mass analysed ion kinetic energy
- SIMS
secondary ion mass spectrometry
- MS/MS
mass spectrometry/mass spectrometry
- HPLC
high performance liquid chromatography
- GlcA
d-gluco-4-enepyranosyluronic acid
- CS
chondroitin sulfate
- DS
dermatan sulfate
- HA
hyaluronan
- UA-GalNAc
2-acetamido-2-deoxy-3-O-(-d-gluco-4-enepyranosyluronic acid)-d-galactose
- UA-GalNAc4S
2-acetamido-2-deoxy-3-O-(-d-gluco-4-enepyranosyluronic acid)-4-O-sulfo-d-galactose
- UA-GalNAc6S
2-acetamido-2-deoxy-3-O-(-d-gluco-4-enepyranosyluronic acid)-6-O-sulfo-d-galactose
- UA2S-GalNAc
2-acetamido-2-deoxy-3-O-(2-O-sulfo--d-gluco-4-enepyranosyluronic acid)-d-galactose
- UA2S-GalNAc4S
2-acetamido-2-deoxy-3-O-(2-O-sulfo--d-gluco-4-enepyranosyluronic acid)-4-O-sulfo-d-galactose
- UA2S-GalNAc6S
2-acetamido-2-deoxy-3-O-(2-O-sulfo--d-gluco-4-enepyranosyluronic acid)-6-O-sulfo-d-galactose
- UA-GalNAcDiS
2-acetamido-2-deoxy-3-O-(-d-gluco-4-enepyranosyluronic acid)-4,6-di-O-sulfo-d-galactose
- UA2S-GalNAcDiS
2-acetamido-2-deoxy-3-O-(2-O-sulfo--d-gluco-4-enepyranosyluronic acid)-4,6-di-O-sulfo-d-galactose
- UA-GlcNAc
2-acetamido-2-deoxy-3-O-(-d-gluco-4-enepyranosyluronic acid)-d-glucose 相似文献
8.
The uptake of 1-14C-dl--aminoadipate in resting mycelium of Penicillium chrysogenum Wis 54-1255 and its metabolism during benzylpenicillin formation were studied. The pH optimum for uptake at 25°C was 6.4. Over a range of concentrations from 0.01–1.0 mM, approximately 45% of 1-14C-dl--aminoadipate was taken up by carbon-starved mycelium. 14CO2 was formed at a low rate, and the total formed amounted to only 1–3% of the 1-14C-dl--aminoadipate supplied. The intracellular pool of -aminoadipate appears to be expandable, depending on the concentration of -aminoadipate in the medium. The rate of penicillin synthesis depended on the intracellular concentration of -aminoadipate. Penicillin biosynthesis achieved half of the maximum rate at an intracellular concentration of 0.06 nmol -aminoadipate/mg dry cell weight. This low concentration, the result of adding 0.01 mM dl--aminoadipate to the medium, was sufficient to reverse the inhibition of penicillin biosynthesis caused by 10 mM extracellular l-lysine. Aminoadipate appears to be recycled during penicillin formation. Labeled -ketoadipate was formed from -aminoadipate to the extent of about 25%.Abbreviation DCW
dry cell weight 相似文献
9.
Teruo Yoshino Minobu Sadamitsu Megumi Minagawa Gerd Reuter Roland Schauer 《Glycoconjugate journal》1988,5(4):377-384
The preparation of benzyl 2,3,6,2,6-penta-O-benzyl--d-lactoside, which is a key intermediate for chemical synthesis of oligosaccharide components of glycosphingolipids, was achieved by an improved method. The 3-O-p-methoxybenzyl and 3-O-methyl derivatives were prepared from benzyl 2,3,6,2,6-penta-O-benzyl--d-lactoside through stannylation. By using benzyl -d-lactoside as starting material, benzyl 3-O-methyl-, 3-O-benzyl- and 3-O-p-methoxybenzyl--d-lactoside were regioselectively synthesized using the same procedure. 相似文献
10.
Mutants of Pseudomonas aeruginosa deficient in the utilization of l-proline as the only carbon and nitrogen source have been found to be defective either in proline dehydrogenase activity or in both proline dehydrogenase and 1-pyrroline-5-carboxylate dehydrogenase activities of the bifunctional proline degradative enzyme. The latter type of mutants was unable to utilize l-ornithine, indicating that a single 1-pyrroline-5-carboxylate dehydrogenase activity is involved in the degradation of ornithine and proline. Proline dehydrogenase and 1-pyrroline-5-carboxylate dehydrogenase activities were strongly and coordinately induced by proline. It was excluded that 1-pyrroline-5-carboxylate acted as an inducer of the bifunctional enzyme and it was shown that the low level induction observed during growth on ornithine was due to the intracellular formation of proline. The formation of the proline degradative enzyme was shown to be subject to catabolite repression by citrate and nitrogen control.Abbreviations EMS
Ethylmethane sulfonate
- NG
N-methyl-N-nitro-N-nitrosoguanidine
- P
Minimal medium P
- Pro-DH
Proline dehydro-genase
- P5C
1-Pyrroline-5-carboxylate
- P5C-DH
1-Pyrroline-5-carboxylate dehydrogenase 相似文献
11.
B. P. Gottikh A. A. Krayevsky M. K. Kukhanova A. A. Jatsyna A. M. Kritzyn C. L. Florentiev 《Molecular biology reports》1973,1(3):173-178
Peptide acceptor properties of phenylalanine and glycine esters of 9-(2,3-dihydroxypropyl-1)-adenine and 1-(2,3-dihydroxypropyl-1)-4-thiouracyl were investigated. All these esters appeared to be powerful inhibitors of polyphenylalanine synthesis in E. coli MRE-600 ribosomes charged with poly U. Like puromycin, esters of adenine derivatives accepted the AcPhe residue from Ac-[14C] Phe-tRNA in a ribosomal system charged with poly U. However, peptidyl esters of 9-(2,3-dihydroxypropyl-1)-adenine remained bound with ribosomes. The structure of the peptide esters synthesized was ascertained after dissociation of ribosomes into subparticles by direct comparison with the synthetic specimens.Abbreviations AcPhe
acetyl-l-phenylalanine
- HP-Ade
9-(2,3-dihydroxypropyl-1)-adenine
- Phe-HP-Ade and Gly-HP-Ade
l-phenylalanine and glycine esters of HP-Ade
- Phe-HP-TUra
l-phenylalanine ester 1-(2,3-dihydroxypropyl-1)-4-thiouracyl
- AcPhePhe-HP-Ade and AcPheGly-HP-Ade
acetyl-l-diphenylalanine and acetyl-l-phenylalanylglycine esters of HP-Ade respectively
- AcPhe-puromycin
acetyl-l-phenylalanyl-puromycin 相似文献
12.
The metabolism of GA29 in maturing seeds of Pisum sativum cv. Progress No. 9 was further investigated, and the utility of 2H-labelled GAs in conjuction with GC-MS is illustrated. Using [2-2H1]GA29 as an internal standard, endogenous GA29 was shown to reach a maximal level (ca. 10 g/seed) 27 days from anthesis, and to decline to ca. 1.6 g/seed in mature seeds. In a time-course feed the metabolism of [2-2H1] [2-3H1]GA29 applied to 27 day old seeds, and of endogenous GA29, was compared from the 1H:2H ratios in the recovered GA29. Although both [2-2H1] [2-3H1]GA29 and endogenous GA29 were metabolised to the same limited extent to a putative conjugate, in the main metabolic process endogenous GA29 was preferentially converted to an untraceable (i.e. unlabelled) metabolite. In contrast, endogenous GA29 and [1,3-2H2] [1,3-3H2]GA29, derived from [1,3-2H2] [1,3-3H2]GA20 in a time-course feed, were metabolised in an identical manner. In the latter case isotope loss precluded identification of the metabolite. The structure (8) has been assigned to a GA catabolite present in maturing seeds and seedlings of pea. The isotope data are consistent with this compound being the hitherto untraced metabolite of GA29 in pea.Abbreviations GAn
gibberellin An
- GC
gas chromatography
- GC-MS
combined gas chromatography-mass spectrometry
- GC-RC
combined gas chromatography-radio counting
- M+
molecular ion
- Me
methyl ester
- RT
retention time
- SICM
selected ion current monitoring
- TLC
thin layer chromatography
- TMS
trimethylsilyl ether 相似文献
13.
Jennifer C. Wilson David C. M. Kong Yu-Teh Li Mark Von Itzstein 《Glycoconjugate journal》1996,13(6):927-931
The mechanism of hydrolysis of 4-methylumbelliferyl 3-deoxy-d-glycero--d-galacto-2-nonulopyranosidonic acid (KDN2MeUmb,4) by KDN-sialidase isolated from the hepatopancreas of the oysterCrassostrea virginica has been monitored by1H NMR spectroscopy. The results of these experiments reveal that KDN-sialidase catalyses the hydrolysis of the synthetic substrate KDN2MeUmb, with initial release of -d-KDN. This is consistent with an overall mechanism for the hydrolysis which proceeds with retention of anomeric configuration. These results agree with earlier NMR studies of otherN-acetylneuraminic acid-recognising sialidases from both viral and bacterial sources. 相似文献
14.
Park S. Nobel 《The Journal of membrane biology》1973,12(1):287-299
Summary Mitochondria isolated from potato tubers were placed in solutions containing various alcohols, aldoses, or neutral amino acids. Based on the osmotic responses in the different media, the reflection coefficients and hence the relative permeabilities of the nonelectrolytes could be determined. The reflection coefficients (
j
'S) of the potato tuber mitochondria for alcohols became progressively larger as hydroxymethyl groups were added to the molecule,viz. methanol (
j
=0.07), ethylene glycol (0.25), glycerol (0.44),meso-erythritol (0.71) and adonitol (0.98). This increase in
j
(decrease in permeativity) with increasing chain length parallels the decreasing lipid-water partition coefficients of the solutes. The reflection coefficients ofd-sorbitol (1.02) and ofd-mannitol (0.99) indicate that these six-carbon polyhydroxy alcohols are relatively impermeant and hence they would be suitable osmotica in which to suspend mitochondria. The
j
'S varied from 0.96 to 1.02 forD-ribose,D-xylose,D-lyxose,D-arabinose, -D-glucose, -D-glucose,D-galactose,D-mannose, glycine,L-alanine,L-threonine,L-phenylalanine,L-methionine andL-cysteine, indicating that these sugars and amino acids do not readily diffuse across the pair of membranes surrounding potato mitochondria. By contrast, the
j
'S of liver mitochondria for glycine and of pea chloroplasts for most of the same aldopentoses and amino acids are close to zero. Thus, different organelles can vary widely in their permeability properties for nonelectrolytes. 相似文献
15.
Sakai T Ishizuka K Shimanaka K Ikai K Kato I 《Marine biotechnology (New York, N.Y.)》2003,5(6):536-544
A fucoidan-utilizing marine bacterium, Fucophilus fucoidanolyticus, was cultivated in medium containing fucoidan from Cladosiphon okamuranus. The C. okamuranus fucoidan was digested into oligosaccharides with the intracellular enzymes of F. fucoidanolyticus, and their structures were determined by nuclear magnetic resonance analyses. Some of their structures are represented by one general structural formula, (-3L-Fucp1-3L-Fucp(4-O-sulfate)1-3L-Fucp(4-O-sulfate)1-3(D-GlcpUA1-2)L-Fucp1)m-3L-Fucp1-3L-Fucp(4-O-sulfate)1-3L-Fucp(4-O-sulfate) 1-3L-Fucp (m = 0, 1, 2, or 3). We concluded that all oligosaccharides obtained were derived from a sulfated-fucose-containing polysaccharide of C. okamuranus, which has a repeating unit of (-3L-Fucp1-3L-Fucp(4-O-sulfate)1-3L-Fucp(4-O-sulfate)1-3(D-GlcpUA1-2)L-Fucp1-). 相似文献
16.
Nobuyoshi Esaki Mutsumi Watanabe Tatsuo Kurihara Kenji Soda 《Archives of microbiology》1994,161(2):110-115
-Dialkylamino acid aminotransferase was found in various fungi; this is the first evidence for the occurrence of the enzyme in eukaryotes. The enzyme was purified from Fusarium solani and shown to be composed of four subunits with an identical molecular weight of 42,000. -Aminoisobutyrate and cycloleucine served as amino donors, and pyruvate, -ketobutyrate, -ketovalerate, -ketoisovalerate, and glyoxylate as amino acceptors. The K
m values for -aminoisobutyrate and -ketobutyrate were 28 and 0.3 mM, respectively. -Ketobutyrate inhibited the enzyme noncompetitively with -aminoisobutyrate, and showed K
i value of 8 mM. The significant inhibitory effect of l-cycloserine was observed, but d-cycloserine did not inhibit the enzyme. The pH and temperature optima for transamination of -aminoisobutyrate with pyruvate were about 8.0 and 60°C, respectively. Despite the production of this enzyme by the mesophile, the enzyme was thermostable; it retained its full activity upon heating at 60°C for 30 min.Abbreviations ACPC
1-aminocyclopropane-1-carboxylic acid
- AIB
-aminoisobutyrate
- PLP
pyridoxal 5-phosphate 相似文献
17.
José M. Castro Paloma Liras Jesús Cortés Juan F. Martín 《Applied microbiology and biotechnology》1985,22(1):32-40
Summary Ammonium and asparagine produced a concentration-dependent reduction of cephamycin C biosynthesis by Streptomyces lactamdurans. Addition of ammonium salts at 1 mM concentration reduced cephamycin biosynthesis by resting cells of S. lactamdurans, whereas concentrations of asparagine above 10 mM were required to get the same effect. High ammonium concentrations decreased glutamine synthetase activity in cell extracts of S. lactamdurans in parallel to the reduction of antibiotic biosynthesis. Ammonium supplementation decreased the pool of glutamic acid and glutamine whereas the intracellular content of ammonium, alanine, and phosphoserine increased significantly. The pool of the tripeptide (l--aminoadipyl)-l-cysteinyl-d-valine, an intermediate in cephamycin biosynthesis, was greatly reduced in ammonium-supplemented cultures. Isopenicillin N synthetase, that converts the tripeptide (l--aminoadipyl)-l-cysteinyl-d-valine to isopenicillin N, isopenicillin N isomerase (that isomerises isopenicillin N to penicillin N) and deacetoxycephalosporin C synthetase (converting penicillin N into deacetoxycephalosporin C) were also reduced in ammonium-supplemented cultures. However, the activities of these enzymes were not inhibited in vitro by 40 mM ammonium, suggesting that the enzymes were repressed but not inhibited by ammonium in vivo. 相似文献
18.
Satoshi Hanzawa Atsushi Odagawa Hidetoshi Sakata Michio Takeuchi Dr. Eiji Ichishima 《Current microbiology》1986,14(4):235-239
Incubation of highly purified -amylase fromAspergillus oryzae (EC 3.2.1.1) with 0.01M acetate buffer, pH 3.0, resulted in degradation of the -amylase. The molecular weight values of degradation products were 42 K, 37 K, and 28 K. Incubation of the purified -amylase in 0.02m phosphate buffer, pH 7.5, at 30°C for 17 h, however, resulted in no degradation of the -amylase molecule.Incubation of the purified -amylase with proangiotensin at pH 3.0 for 24 h resulted in cleavage of Tyr4-Ile5, His6-Pro7, Pro7-Phe8, Phe8-His9, and His9-Leu10. Thus, it appears that proteolytic activities firmly bound to -amylase are identical withAspergillus aspartic proteinase (EC 3.4.23.6) andAspergillus acid carboxypeptidase (EC 3.4.16.1). 相似文献
19.
Effects of Na+, H+, and Cl− on alanine transport by lobster hepatopancreatic brush border membrane vesicles 总被引:1,自引:1,他引:0
Gregory A. Ahearn Marilyn L. Grover Ronald E. Dunn 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1986,156(4):537-548
Summary Epithelial brush border membrane vesicles (BBMV) of lobster hepatopancreas were formed by a magnesium precipitation technique previously described (Ahearn et al. 1985).3H-l-alanine transport by these vesicles was sodium and potassium insensitive, in contrast to a strong Na-dependency exhibited by3H-d-glucose transport. Initial alanine entry rates (15 s uptake) were stimulated and transient alanine uptake overshoots were observed when external pH was acidic (e. g. pH 4.0, 5.0 or 6.0) and a Cl gradient was imposed across the vesicular wall; at pHo=7.4 alanine uptake was reduced in rate and hyperbolic in character. Alanine uptake from an acidic extravesicular environment in the absence of Cl responded to a transmembrane electrical potential difference created by an outwardly-directed, valinomycin-induced, potassium diffusion potential, suggesting that the alanine molecule alone carried sufficient charge under these conditions to respond to the electrical gradient. External 5.0 mMl-lysine andl-serine similarly inhibited the influx and overshoot properties of 0.05 mM3H-l-alanine uptake, whereas 5.0 mMl-leucine had virtually no effect. Trans-stimulation of alanine initial uptake rates and an enhancement of alanine accumulation against a concentration gradient were observed by vesicles preloaded with 1 mMl-lysine, but not by vesicles lacking amino acids or those containing 1 mMl-leucine orl-serine.3H-l-alanine influx from acidic external environments in the presence of a Cl gradient occurred by a combination of carrier-mediated transfer and apparent diffusion. Decreasing pHo from 6.0 to 4.0 elevated alanineK
t from 0.55 to 2.64 mM, while alanineJ
M increased from 55 to 550 pmol/mg protein· 15 s. Apparent diffusional permeability of the membranes to alanine under these conditions increased slightly. These results suggest, but do not conclusively prove, that alanine transport across BBMV of lobster hepatopancreas may occur by way of a classical y+ transprot protein at acidic pH. The extent of this transport is determined by the magnitude of the transmembrane chloride gradient which serves as a powerful driving force for cationic amino acids in this tissue. 相似文献
20.
Tyson S. Ikeda Eun-Sil Hwang Michael J. Coady Bruce A. Hirayama Matthias A. Hediger Ernest M. Wright 《The Journal of membrane biology》1989,110(1):87-95
Summary The Na+/glucose cotransporter from rabbit intestinal brush border membranes has been cloned, sequenced, and expressed inXenopus oocytes. Injection of cloned RNA into oocytes increased Na+/sugar cotransport by three orders of magnitude. In this study, we have compared and contrasted the transport properties of this cloned protein expressed inXenopus oocytes with the native transporter present in rabbit intestinal brush borders. Initial rates of14C--methyl-d-glucopyranoside uptake into brush border membrane vesicles andXenopus oocytes were measured as a function of the external sodium, sugar, and phlorizin concentrations. Sugar uptake into oocytes and brush borders was Na+-dependent (Hill coefficient 1.5 and 1.7), phlorizin inhibitable (K
i
6 and 9 m), and saturable (-methyl-d-glucopyranosideK
m
110 and 570 m). The sugar specificity was examined by competition experiments, and in both cases the selectivity wasd-glucose>-methyl-d-glucopyranoside>d-galactose>3-O-methyl-d-glucoside. In view of the close similarity between the properties of the cloned protein expressed in oocytes and the native brush border transporter, we conclude that we have cloned the classical Na+/glucose cotransporter. 相似文献