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1.
Contemporary research hypothesizes that biological inheritance and ontogenetic factors shape the development of gestural communication
in nonhuman great apes. However, little is known about the specific role that mothers play in the acquisition of their infants’
gestures. We observed 6 bonobo (Pan paniscus) and 4 chimpanzee (Pan troglodytes) mother–infant dyads and recorded their gesture types and frequency. We analyzed all behavioral contexts in which gestures
occurred as well as the play context alone. Infants of both species were unlikely to share gestures with their mother or unrelated
adult females. However, gestural sharing was prevalent within age groups. Within and across species, infant–infant and mother–mother
groups were homogeneous regarding the types of gestures they shared, although there was individual variation in the frequency
of gesture use. Our findings provide limited evidence that infants learned their gestures by imitating their mothers. Phylogenetic
influences seem to be vital in gestural acquisition but, we suggest, repertoire development cannot be disentangled from individual
social encounters during life. 相似文献
2.
A longitudinal study of chimpanzee gestural communication is reported. Subjects were seven 5- to 8-year-old members of a semi-natural
group at the Yerkes Field Station. These were the same individuals observed byTomasello et al. (1985) four years previously. Nearly identical operational definitions and observational procedures were used in the
two studies. Longitudinal comparisons between the two observation periods revealed that the development of chimpanzee gestural
communication is best characterized as a series of ontogenetic adaptations: as particular social functions (e.g., nursing,
playing, grooming, etc.) arise, decline, or change, gestural communication follows suit. Most gestures seem to be conventionalized
by individuals in direct social interaction with conspecifics. Some gestures may be learned by “second-person imitation”—an
individual copying a behavior directed to it by another individual. No evidence was found for “third-person imitation”—an
individual copying a gesture used between two other individuals. Implications for the concept of chimpanzee “culture” are
discussed.
This research was supported in part by NIH Grant RR-00165 from the Division of Research Resources to the Yerkes Regional Primate
Research Center. The Yerkes Center is fully accredited by the American Association for the Accreditation of Laboratory Animal
Care. 相似文献
3.
According toFiedler (1956) the pygmy chimpanzee is considered to be a separate species of the pongidae. Therefore, our investigations with a
young female pygmy chimpanzee had two special aims. First, we hoped to collect some facts concerning the transferability of
the experiments ofPremack (1971) within the great apes; he investigated the language skills of a common chimpanzee. Besides, we wanted to test the
intellectual abilities of this littel known primate species.
Pieces of wood, differing in color and shape, were used as symbols. At both sides, there was a magnet to hang them on an iron
board. The subject had to choose between two or more signs out of three groups: food symbols, activity symbols and quantity
symbols. The hanging up of one, later of two correlated symbols was followed by a special event for each of them. There is
high concordance between the subject’s preferring of events and its preferring of symbols. The correlation-coefficient for
food and food signs is as high as 0.95. Nearly without mistake is the subject’s use of the much/little signs in connection
with the food symbols. The rate of error in general is between 10–20% and is in accordance to the corresponding results mentioned
byPremack (1971). The way the subject learned the meaning of the symbols changed from slow to sudden comprehension. In general, these
results provide further evidence of the high intelligence level of pygmy chimpanzees.
相似文献
4.
A protocol has been developed for the induction of somatic embryogenesis from flower explants of chamomile (Chamomilla recutita L.). The effects of several plant growth regulators [α-naphthylacetic acid (NAA), 2,4-dichlorophenoxyacetic acid, 6-benzyladenine (BA) and kinetin (Kin), alone or in combination]
and the flower type (disk or ray flower) were investigated. Both types of flowers responded to the callus and shoot induction
treatments, but formation of globular somatic embryos took place only on disk-flower-derived explants after 2–4 weeks of culture
on a Murashige and Skoog (MS) medium supplemented either with 8.87 μm BA and 1.07 μm NAA or with 26.8 μm NAA and 11.5 μm Kin. However, fully developed, cotyledonary-stage somatic embryos could be induced only on the NAA/Kin medium, 10 weeks after
culture initiation. Germination of the embryos and plant regeneration took place after subculture for 4–5 weeks onto medium
of the same composition. Plantlets regenerated from embryos flowered in vitro on a MS medium supplemented with 8.87 μm BA and 1.07 μm NAA. The significance of the results with respect to chamomile micropropagation and the utilization of wild populations in
breeding programs is discussed.
Received: 6 April 1998 / Revision received: 12 October 1998 / Accepted: 28 October 1998 相似文献
5.
Regeneration and large-scale propagation of bamboo (Dendrocalamus strictus Nees) through somatic embryogenesis 总被引:1,自引:0,他引:1
A complete protocol for large-scale propagation of Dendrocalamus strictus Nees by somatic embryogenesis has been developed. Seeds cultured on agar-solidified Murashige and Skoog (MS) medium supplemented
with 2,4-dichlorophenoxyacetic acid (2,4-D; 3×10–5
m) produced embryogenic callus from proliferation of the embryo. Somatic embryos formed in vitro multiplied rapidly (two- to
five fold every 5 weeks) on semi-solid MS medium containing 2,4-D (1×10–5
m), kinetin (Kn) (5×10–6
m), 1-indolebutyric acid (IBA) (2×10–6
m) and soluble polyvinylpyrrolidone (PVP) (250 mg l–1), or MS with 2,4-D (1×10–5
m), 6-benzylaminopurine (BAP) (1×10–5
m), and soluble PVP (250 mg l–1). Upon transfer to MS containing 1-naphthaleneacetic acid (NAA) (5×10–6
m), Kn (5×10–6
m) and soluble PVP (250 mg l–1), the dark-green embryos developed into healthy plantlets. Unrooted shoots, if any, obtained on the multiplication media
were rooted on MS major salts reduced to half strength supplemented with NAA (3×10–6
m) and IBA (2.5×10–6
m). The rooted plants were successfully transferred to soil in polythene bags with over 80% survival. Using this methodology,
more than 100,000 plants have been produced.
Received: 16 April 1998 / Revision received: 25 September 1998 / Accepted: 10 October 1998 相似文献
6.
Plant regeneration via somatic embryogenesis, and transient gene expression in sweet potato protoplasts 总被引:1,自引:0,他引:1
A method for regenerating plants from petiole protoplasts of the in vitro-raised sweet potato cultivar Jewel is described.
Protoplast yields of 3.0–5.0×106 were obtained following 4–6 h digestion of 1- to 2-cm petioles (1 g fresh weight) with 1% Cellulase-R10, 2% Macerozyme-R10,
and 0.3% Pectolyase Y-23 in a washing solution with 9% mannitol. A plating density of 105 protoplasts/ml was optimal for subsequent division. An initial division frequency of 12–15% was obtained in liquid or agarose-solidified
KP8 culture medium supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) (0.9 μm), and zeatin (2.3 μm). Colonies consisting of 100–200 cells were formed after 4 weeks in the dark at 24±2°C. The frequency of colony formation
was improved by the gradual addition of fresh liquid KP8 medium of lower osmoticum. Protocalli (1–2 mm in diameter) were formed
after an additional 4–6 weeks under continuous illumination and regular dilution with fresh culture medium. Morphogenic callus
formed globular and heart-shaped embryos that developed into cotyledon stage embryos, following transfer of calli onto medium
containing 2,4-D (11.3 μm) and benzylaminopurine (2.2 μm). Subsequently, embryo conversion to plantlets was obtained on basal medium with 2% sucrose and 3.5 μm gibberellic acid. Regenerated plantlets were successfully transplanted in soil. Mature plants appeared phenotypically normal.
The same petiole protoplast populations showed transient expression of the gusA gene introduced using electroporation.
Received: 10 October 1997 / Revision received: 10 February 1998 / Accepted: 2 March 1998 相似文献
7.
Somatic embryogenesis and in vitro rosmarinic acid accumulation in Salvia officinalis and S. fruticosa leaf callus cultures 总被引:1,自引:0,他引:1
The effect of explant age, plant growth regulators and culture conditions on somatic embryogenesis and rosmarinic acid production
from leaf explants of Salvia officinalis and S. fruticosa plants collected in Greece was investigated. Embryogenic callus with numerous spherical somatic embryos could be induced
on explants derived from both species and cultured for 3 weeks on a Murashige and Skoog (MS) medium supplemented with 1.8–18
μm 2,4-dichlorophenoxyacetic acid (2,4-D) and kinetin (Kin) or 10.5–21 μm 1-naphthalenacetic acid and 6-benzyladenine. Only explants from young plants (with six to eight leaves) responded to the
culture treatments and, in general, low light intensities (50 μmol m–2 s–1) favoured callus formation and induction of somatic embryos. Somatic embryos were further developed on the same medium. Heart-
and torpedo-shaped embryos (1–2 mm long) were subcultured on a growth-regulator-free MS medium for maturation. Maximum rosmarinic
acid accumulation in S. officinalis and S. fruticosa callus cultured on 4.5 μm 2,4-D and 4.5 μm Kin was 25.9 and 29.0 g/l, respectively.
Received: 17 January 1997 / Revision received: 26 May 1997 / Accepted: 30 June 1997 相似文献
8.
Evidence for NO-dependent vasodilation in the trout (Oncorhynchus mykiss ) coronary system 总被引:1,自引:0,他引:1
T. Mustafa C. Agnisola J. K. Hansen 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(2):98-104
The effects of l-arginine, and its analogues N
ω-nitro-l-arginine methyl ester and N
ω-nitro-l-arginine on vascular resistance were investigated in the intact coronary system of an isolated non-working trout heart preparation.
l-Arginine, at 10–8 mol · l–1induced a slight vasodilatory effect (max 10%). N
ω-nitro-l-arginine methyl ester and N
ω-Nitro-l-arginine in the range 10–8–10–4 mol · l–1 caused dose-dependent increases in coronary resistance. The vasodilatory action of l-arginine was abolished when the preparation was pretreated with 10–4 mol · l–1
N
ω-nitro-l-arginine or N
ω-nitro-l-arginine methyl ester. Nitroprusside alone at 1 mmol · l–1 induced a maximum vasodilation (30%) of the coronary system. Methylene blue a known inhibitor of guanylate cyclase, induced
a strong vasoconstriction (already significant at 10–5 mol · l–1) and was able to overcome the vasodilative effect of nitroprusside. The endothelial nitric oxide agonists acetylcholine and
serotonin, established in mammalian vessels, also mediate vasodilation in trout coronary system. In 50% of preparations, acetylcholine
induced a biphasic response with vasodilation at low concentration (max 15% at 10–8 mol · l–1). Serotonin displayed a dose-response vasodilation in the range 10–8–10–4 mol · l–1 (max 20%). These vasodilative effects were reduced or abolished by 10–4 mol · l–1
l-NA. These data support the existence of NO-mediated vasodilation mechanisms in the trout coronary system.
Accepted: 1 July 1996 相似文献
9.
S. S. Sudge K. B. Bastawde D. V. Gokhale U. R. Kalkote T. Ravindranathan 《Applied microbiology and biotechnology》1998,49(5):594-599
About 1000 bacterial colonies isolated from sea water were screened for their ability to convert dl-5-phenylhydantoin to d(−)N-carbamoylphenylglycine as a criterion for the determination of hydantoinase activity. The strain M-1, out of 11 hydantoinase-producing
strains, exhibited the maximum ability to convert dl-5-phenylhydantoin to d(−)N-carbamoylphenylglycine. The strain M-1 appeared to be a halophilic Pseudomonas sp. according to morphological and physiological characteristics. Optimization of the growth parameters revealed that nutrient
broth with 2% NaCl was the preferred medium for both biomass and enzyme production. d-Hydantoinase of strain M-1 was not found to be inducible by the addition of uracil, dihydrouracil, β-alanine etc. The optimum
temperature for enzyme production was about 25 °C and the organism showed a broad pH optimum (pH 6.5–9.0) for both biomass
and hydantoinase production. The organism seems to have a strict requirement of NaCl for both growth and enzyme production.
The optimum pH and temperature of enzyme activity were 9–9.5 and 30 °C respectively. The biotransformation under the alkaline
conditions allowed the conversion of 80 g l−1
dl-5-phenylhydantoin to 82 g l−1
d(−)N-carbamoylphenylglycine within 24 h with a molar yield of 93%.
Received: 15 September 1997 / Received revision: 5 January 1998 / Accepted: 6 January 1998 相似文献
10.
Friable embryogenic callus and somatic embryo formation from cotyledon explants of African marigold (Tagetes erecta L.) 总被引:3,自引:0,他引:3
Embryogenic callus and somatic embryos were induced from cotyledonary explants of African marigold (Tagetes erecta L.). Cotyledons were first cultured on MS medium supplemented with 2.0 mg l–1 2,4-D and 0.2 mg l–1 kinetin. After 5 weeks, calli were transferred to MS medium supplemented with 0.02 mg l–1 thidiazuron where compact embryogenic callus developed. Friable embryogenic callus developed when the compact embryogenic
callus was transferred to medium containing 2,4-D and subcultured every 2 weeks. Friable embryogenic callus has been maintained
for more than 2 years without losing the capacity to generate embryos. Embryo development was obtained when friable embryogenic
callus was transferred to MS medium supplemented with 3 mg l–1 ABA and 60 g l–1 sucrose. The addition of 10–30 mM
l-glutamine improved embryo development.
Received: 13 May 1997 / Revision received: 24 February 1998 / Accepted: 28 March 1998 相似文献
11.
Three different types of β-d-galactosidase (EC 3.2.1.23) could be distinguished in rabbit tissues using electrophoretic procedures. (1) Acid β-d-galactosidase with a low mobility and maximal activity atpH 3–5 was found in the particulate fraction of various tissue homogenates. This enzyme hydrolyzed 4-methylumbelliferyl-d-galactoside, but no activity against other glycoside substrates could be demonstrated. The enzyme was inhibited by galactono-(1
→ 4)-lactone. (2) Lactose-hydrolyzing β-d-galactosidase with an intermediate mobility was found only in juvenile small intestine. Most of the activity was found in
the particulate fraction of the cell. The enzyme hydrolyzed several other synthetic glycoside substrates besides lactose.
It was most active atpH 5–6 and strongly inhibited by glucono-(1 → 5)-lactone but not much affected by galactono-(1 → 4)-lactone. (3) Neutral β-d-galactosidase with a fast mobility and maximal activity atpH 6–8 was found in the soluble fraction of homogenates from liver, kidney, and small intestine. This enzyme also showed a
broad substrate specificity; it possessed activity against aryl-β-d-glucoside, -fucoside, and -galactoside substrates but not against lactose. The enzyme was strongly inhibited by glucono-(1
→ 5)-lactone and (less) by galactone-(1 → 4)-lactone. Neutral β-d-galactosidase and neutral β-d-glucosidase (EC 3.2.1.21) are probably identical enzymes in the rabbit. Individual variation, in both electrophoretic mobility
and activity, was found for neutral β-d-galactosidase. Genetic analysis of the electrophoretic variants revealed that two alleles at an autosomal locus are responsible
for this variation.
This investigation was supported in part by Public Health Service Grant RR-00251 from the Division of Research Resources and
by funds of the University of Utrecht. 相似文献
12.
Park Y Zhang Z Laremore TN Li B Sim JS Im AR Ahn MY Kim YS Linhardt RJ 《Glycoconjugate journal》2008,25(9):863-877
Acharan sulfate content from African giant snail (Achatina fulica) was compared in eggs and snails of different ages. Acharan sulfate was not found in egg. Acharan sulfate disaccharide →4)-α-d-GlcNpAc (1→4)-α-l-IdoAp2S(1→, analyzed by SAX (strong-anion exchange)–HPLC was observed soon after hatching and increases as the snails grow.
Monosaccharide compositional analysis showed that mole % of glucosamine, a major monosaccharide of acharan sulfate, increased
with age while mole % of galactose decreased with age. These results suggest that galactans represent a major energy source
during development, while acharan sulfate appearing immediately after hatching, is essential for the snail growth. The structures
of neutral N-glycans released from eggs by peptide N-glycosidase F (PNGase F), were next elucidated using ESI-MS/MS, MALDI-MS/MS, enzyme digestion, and monosaccharide composition
analysis. Three types of neutral N-glycan structures were observed, truncated (Hex2–4-HexNAc2), high mannose (Hex5–9-HexNAc2), and complex (Hex3-HexNAc2–10) types. None showed core fucosylation. 相似文献
13.
Pei-Wen Hsieh Li-Chi Hsu Chern-Hsiung Lai Chin-Chung Wu Tsong-Long Hwang Yin-Ku Lin Yang-Chang Wu 《World journal of microbiology & biotechnology》2009,25(8):1461-1469
The endophytic extracts from 19 endophytes, isolated from 13 species of Taiwanese plants, were evaluated for biological activity,
including cytotoxicity, anti-platelet aggregation, and anti-inflammatory activity. The extracts of 12 endophytes exhibited
inhibitory effects on collagen-induced platelet aggregation with IC50 values of 19.85–87.64 μg/ml. Four strains, Rahnella aquatilis, Pantoea agglomerans, Rhodotorula sp., and Penicillium paxilli, also showed inhibitory effects on thrombin-induced platelet aggregation with IC50 values of 42.80–61.54 μg/ml. Additionally 12 extracts of endophytes exhibited cytotoxicities with IC50 values of 0.12–19.83 μg/ml. However, eight extracts revealed inhibitory effects on superoxide anion generation induced by
fMLP (N-formyl-l-methionyl-l-leucyl-l-phenylalanine) in human neutrophils. The extract of Rahnella aquatilis showed anti-platelet aggregation activity, and bioassay-directed fractionation led to the isolation of six compounds, including
one isoalloxazine: lumichrome (1); two isoflavones: genistein (2) and daidzein (3); two cyclic peptides: cyclo-Pro-Val (4)
and cyclo-Pro-Phe (5); and one benzenoid: methyl 2,4,5-trimethoxybenzoate (6). These results indicated that endophytes from
Taiwanese herbal plants could be useful sources for research and development of bioactive lead compounds from nature. 相似文献
14.
G. Zimmermann 《BioControl》1978,23(2):181-187
Zusammenfassung Von pilzbefallenen Larven der KohlschabePlutella maculipennis
Curt. wurdeEntomophthora blunckii
Lakon exZimmermann isoliert. Die Art wird mit lateinischer Diagnose gültig beschrieben, die morphologischen Merkmale werden erg?nzend angegeben
und erstmals durch Fotos belegt.E. blunckii w?chst gut auf koaguliertem Eidotter, weniger gut auf Sabouraud-Glucose-Agar. Mycelwachstum wurde zwischen 8° und 28°C beobachtet,
dagegen nicht bei 32°C. Die Symptome infizierter Larven werden geschildert und der Pilz wird mit ?hnlichen Arten verglichen.
Summary Entomophthora blunckii Lakon exZimmermann was isolated from larvae of the diamondback-mothPlutella maculipennis Curt. and redescribed. The fungus is characterized by its elliptical to pear-shaped conidia (from infected larvae 13–20×7–11 μm, mostly 15–18×7–9 μm) with the outer membrane often inflated and its branched conidiophores forming a dense gray to faint greenish-yellowish covering over the body of the insect. The symptoms of larvae infected withE. blunckii are described. The species grows on coagulated egg yolk, less well on Sabouraud-Dextrose-Agar. Growth was observed between 8° and 28°C but not at 32°C. The fungus is compared with similar species.相似文献
15.
Yi-Guang Chen Shu-Kun Tang Yu-Qin Zhang Zhu-Xiang Liu Qi-Hui Chen Jian-Wu He Xiao-Long Cui Wen-Jun Li 《Extremophiles : life under extreme conditions》2010,14(4):397-402
A novel moderately halophilic, alkaliphilic, non-motile, non-sporulating, catalase-positive, oxidase-negative, aerobic, coccus-shaped,
Gram-positive bacterium, designated strain JSM 071043T, was isolated from a subterranean brine sample collected from a salt mine in Hunan Province, China. Growth occurred with
0.5–20% (w/v) NaCl (optimum 5–10%) at pH 6.5–10.5 (optimum pH 8.5) and at 10–40°C (optimum 25–30°C). Good growth also occurred
in the presence of 0.5–20% (w/v) KCl (optimum 5–8%) or 0.5–25% (w/v) MgCl2·6H2O (optimum 5–10%). The peptidoglycan type was A4α (l-Lys–l-Ala–l-Glu) and major cell-wall sugars were tyvelose and mannose. The major cellular fatty acids were anteiso-C15:0, iso-C16:0 and anteiso-C17:0. Strain JSM 071043T contained MK-9 and MK-8 as the predominant menaquinones and diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol
as the major polar lipids. The DNA G + C content was 67.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed
that strain JSM 071043T was a member of the suborder Micrococcineae, and was most closely related to Zhihengliuella halotolerans YIM 70185T (sequence similarity 98.9%) and Zhihengliuella alba YIM 90734T (98.2%), and the three strains formed a distinct branch in the phylogenetic tree. The combination of phylogenetic analysis,
DNA–DNA relatedness values, phenotypic characteristics and chemotaxonomic data supports the proposal that strain JSM 071043T represents a novel species of the genus Zhihengliuella, for which the name Z. salsuginis sp. nov. is proposed. The type strain is JSM 071043T (= DSM 21149T = KCTC 19466T). 相似文献
16.
This article describes conditions to optimize the yield of viable protoplasts from callus tissue of Asparagus densiflorus cv. Sprengeri and their subsequent regeneration into plantlets. Callus tissue was initiated by culturing spear sections (5–7
mm) on Murashige and Skoog (MS) medium supplemented with 0.8% (wt/vol) Bacto agar, 3% (wt/vol) sucrose, 0.5 mg/l each of nicotinic
acid, pyridoxine-HCl, and thiamine-HCl, 1 mg/l p-chlorophenoxyaceticacid (pCPA) and 1 mg/l 6-benzylaminopurine (BAP). The maximum protoplast yield was obtained in a mixture
of 1% (wt/vol) Cellulysin, 0.8% (wt/vol) Rhozyme HP 150 and 0.3% (wt/vol) Macerase, dissolved in cell protoplast wash salt
solution with 7 mm CaCl2
.2H2O, 3 mm MES, 0.6 m glucose, and 0.1 m mannitol. First divisions were observed after 3–4 days of initial culture. The plating efficiency was highest (7.8%) in half-strength
MS semisolid medium containing 1 g/l glutamine, 0.6 m glucose, 0.1 m mannitol, 0.5 mg/l folic acid, 0.05 mg/l biotin, 2 mg/l ascorbic acid, 1 mg/l α-naphthaleneacetic acid, 0.5 mg/l zeatin, and 0.1% (wt/vol) Gelrite. Protoplast-derived microcolonies and microcalli were
cultured on the same medium on which the primary callus culture was initiated. After 10–12 weeks, calli were transferred to
shoot regeneration medium containing MS salts, 1 mg/l BAP, 0.5 mg/l pCPA and 0.2% Gelrite. Shoots (3–4 cm) were then transferred
to MS rooting medium with 2 mg/l indole-3-butyric acid, and 0.2% Gelrite. Plantlets were obtained within 4–5 weeks.
Received: 9 August 1995 / Revision received: 27 June 1997 / Accepted: 17 July 1997 相似文献
17.
The dichotomy between the two Pan species, the bonobo (Pan paniscus) and chimpanzee (Pan troglodytes) has been strongly emphasized until very recently. Given that most studies were primarily based on adult individuals, we shifted the “continuity versus discontinuity” discussion to the infant and juvenile stage. Our aim was to test quantitatively, some conflicting statements made in literature considering species differences between immature bonobos and chimpanzees. On one hand it is suggested that infant bonobos show retardation in motor and social development when compared with chimpanzees. Additionally it is expected that the weaning process is more traumatic to chimpanzee than bonobo infants. But on the other hand the development of behaviors is expected to be very similar in both species. We observed eight mother–infant pairs of each species in several European zoos. Our preliminary research partially confirms that immature chimpanzees seem spatially more independent, spending more time at a larger distance from their mother than immature bonobos. However, the other data do not seem to support the hypothesis that bonobo infants show retardation of motor or social development. The development of solitary play, environmental exploration, social play, non-copulatory mounts and aggressive interactions do not differ between the species. Bonobo infants in general even groom other group members more than chimpanzee infants. We also found that older bonobo infants have more nipple contact than same aged chimpanzees and that the weaning process seems to end later for bonobos than for immature chimpanzee. Additionally, although immature bonobos show in general more signs of distress, our data suggest that the weaning period itself is more traumatic for chimpanzees. 相似文献
18.
The regulation of homoserine dehydrogenase activity was studied in nineAzotobacter strains belonging to five different species. In all the species the enzyme is subject to feedback inhibition byl-threonine andl-isoleucine, the first being much more active as inhibitor. The inhibition byl-threonine is noncompetitive with respect to NADPH and of mixed type with respect to aspartate-Β-semialdehyde; the inhibition
byl-isoleucine is noncompetitive with respect to both substrates. The synthesis of homoserine dehydrogenase inAzotobacter chroococcum I.P. is somewhat repressed by 1mm l-methionine and 5mm l-isoleucine. In all the strains examined either NADPH or NADH can serve as cofactors for this activity, though the ratio of
activity with the two pyridine nucleotides (NADPH/NADH) shows higher values (3.3–3.8) in the speciesmacrocytogenes andinsignis than in thechroococcum, beijerinckii andvinelandii group (1.5–1.6). The pattern of control of this enzyme in the genusAzotobacter is discussed in relation to other bacterial homoserine dehydrogenases.
We are grateful to Dr. G. N. Cohen, Service de Physiologie Microbienne, Institut Pasteur, Paris, for helpful discussions and
encouragements. 相似文献
19.
Bradyrhizobium japonicum, the nitrogen-fixing symbiotic partner of soybean, was grown on various carbon substrates and assayed for the presence of
the glyoxylate cycle enzymes, isocitrate lyase and malate synthase. The highest levels of isocitrate lyase [165–170 nmol min–1 (mg protein)–1] were found in cells grown on acetate or β-hydroxybutyrate, intermediate activity was found after growth on pyruvate or galactose,
and very little activity was found in cells grown on arabinose, malate, or glycerol. Malate synthase activity was present
in arabinose- and malate-grown cultures and increased by only 50–80% when cells were grown on acetate. B. japonicum bacteroids, harvested at four different nodule ages, showed very little isocitrate lyase activity, implying that a complete
glyoxylate cycle is not functional during symbiosis. The apparent K
m of isocitrate lyase for d,l-isocitrate was fourfold higher than that of isocitrate dehydrogenase (61.5 and 15.5 μM, respectively) in desalted crude extracts
from acetate-grown B. japonicum. When isocitrate lyase was induced, neither the V
max nor the d,l-isocitrate K
m of isocitrate dehydrogenase changed, implying that isocitrate dehydrogenase is not inhibited by covalent modification to
facilitate operation of the glyoxylate cycle in B. japonicum.
Received: 10 October 1997 / Accepted: 16 January 1998 相似文献
20.
Vidal L Calveras J Clapés P Ferrer P Caminal G 《Applied microbiology and biotechnology》2005,68(4):489-497
The glyA gene encoding a serine hydroxymethyl transferase (SHMT) with threonine aldolase activity was isolated from Streptococcus thermophilus YKA-184 chromosomal DNA. This aldolase is a pyridoxal 5′-phosphate-dependent enzyme that stereospecifically catalyzes the
interconversion of l-threonine to glycine and acetaldehyde. The enzyme was overexpressed in Escherichia coli M15 as a recombinant protein of 45 kDa with a His6-tag at its N-terminus. The recombinant enzyme was purified to homogeneity
by a single chromatographic step using Ni-nitrilotriacetic acid affinity, obtaining a high activity-recovery yield (83%).
Lyophilized and precipitated enzymes were stable at least for 10 weeks when stored at −20°C and 4°C. It was observed that
the K
m for l-allo-threonine was 38-fold higher than that for l-threonine, suggesting this enzyme can be classified as a specific l-allo-threonine aldolase. The optimum pH range of threonine aldolase activity for the recombinant SHMT was pH 6–7. When tested
for aldol addition reactions with non-natural aldehydes, such as benzyloxyacetaldehyde and (R)-N-Cbz-alaninal, two possible β-hydroxy-α-amino acid diastereoisomers were produced, but with moderate stereospecificity. The
enzyme showed potential as a biocatalyst for the stereoselective synthesis of β-hydroxy-α-amino acids. 相似文献