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1.
In-vitro-grown cells of Mucuna pruriens, immobilized in calcium-alginate gels, were able to transform the precursor L-tyrosine into L-dihydroxyphenylalanine (L-DOPA). After the immobilization in alginate the plant cells released 90% of the produced L-DOPA into the medium; supplementation of the medium with calcium inhibited both the transformation of L-tyrosine into L-DOPA and the release of L-DOPA into the medium. Continuous illumination of the beads had a slight beneficial effect on the synthesis of L-DOPA. A simple production medium for the transformation of L-tyrosine into L-DOPA was designed. This medium contained only sucrose and sodium chloride as osmotic stabilizers, a low concentration of calcium chloride for stabilization of the alginate beads, and L-tyrosine as the precursor. 相似文献
2.
The Drosophila melanogaster gene flightless-I, involved in gastrulation and
muscle degeneration, has Caenorhabditis elegans and human homologues. In
these highly conserved genes, two previously known gene families have been
brought together, families encoding the actin- binding proteins related to
gelsolin and the leucine-rich-repeat (LRR) group of proteins involved in
protein-protein interactions. Both these gene families exhibit
characteristics of molecular changes involving replication slippage and
exon shuffling. Phylogenetic analyses of 19 amino acid sequences of 6
related protein types indicate that actin- associated proteins related to
gelsolin are monophyletic to a common ancestor and include flightless
proteins. Conversely, comparison of 24 amino acid sequences of LRR proteins
including the flightless proteins indicates that flightless proteins are
members of a structurally related subgroup. Included in the flightless
cluster are human and mouse rsp-1 proteins involved in suppressing v-Ras
transformation of cells and the membrane-associated yeast (Saccharomyces
cerevisae) adenylate cyclase whose analogous LRRs are required for
interaction with Ras proteins. There is a strong possibility that ligands
for this group could be related and that flightless may have a similar role
in Ras signal transduction. It is hypothesized that an ancestral monomeric
gelsolin precursor protein has undergone at least four independent gene
reorganization events to account for the structural diversity of the extant
family of gelsolin-related proteins and that gene duplication and exon
shuffling events occurred prior to or at the beginning of multicellular
life, resulting in the evolution of some members of the family soon after
the appearance of actin-type proteins.
相似文献
3.
From cells of Mucuna pruriens, grown in suspension, a monophenol monooxygenase (EC 1.14.18.1) was purified to homogeneity, as deduced from sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme appeared to have a native molecular weight of 90000±5000 dalton, and consisted of two subunits, each of 42000±1000 dalton. High-performance liquid chromatography with electrochemical detection for specific measurement of catecholes, was used to determine separately the tyrosinehydroxylating and catecholase activities of the enzyme. For the enzymatic activities, pH optima of, respectively, 7.5 and 5.5–6.5 were found; the effects of some inhibitors on both activities appeared to be different. Michaelis-Menten characteristics for some mono-and o-dihydroxysubstrates were determined.Abbreviations DEAE
diethylaminoethyl
- HPLC
high-performance liquid chromatography
- L-DOPA
L-3,4-dihydroxyphenylalanine 相似文献
4.
Magnesium-induced inner membrane aggregation in heart mitochondria: prevention and reversal by carboxyatractyloside and bongkrekic acid 下载免费PDF全文
Mg(2+) at an optimal concentration of 2mM (ph 6.5) induces large increases (up to 30 percent) in the optical density of bovine heart mitochondria incubated under conditions of low ionic strength (< approx. 0.01). The increases are associated with aggregation (sticking together) of the inner membranes and are little affected by changes in the energy status of the mitochondria. Virtually all of a number of other polyvalent cations tested and Ag(+) induce increases in mitochondrial optical density similar to those induced by Mg(2+), their approximate order of concentration effectiveness in respect to Mg(2+) being: La(3+) > Pb(2+) = Cu(2+) > Cd(2+) > Zn(2+) > Ag(+) > Mn(2+) > Ca(2+) > Mg(2+). With the exception of Mg(2+), all of these cations appear to induce swelling of the mitochondria concomitant with inner membrane aggregation. The inhibitors of the adenine nucleotide transport reaction carboxyatratyloside and bongkrekic acid are capable of preventing and reversing Mg(2+)-induced aggregation at the same low concentration required for complete inhibition of phosphorylating respiration, suggesting that they inhibit the aggregation by binding to the adenine nucleotide carrier. The findings are interpreted to indicate (a) that the inner mitochondrial membrane is normally prevented from aggregating by virtue of its net negative outer surface change, (b) that the cations induce the membrane to aggregate by binding at its outer surface, decreasing the net negative charge, and (c) that carboxyatractyloside and bongkrekic acid inhibit the aggregation by binding to the outer surface of the membrane, increasing the net negative charge. 相似文献
5.
In diffuse growing cells the orientation of cellulose fibrils determines mechanical anisotropy in the cell wall and hence also the direction of plant and organ growth. This paper reports on the mean or net orientation of cellulose fibrils in the outer epidermal wall of the whole Arabidopsis plant. This outer epidermal wall is considered as the growth-limiting boundary between plant and environment. In the root a net transverse orientation of the cellulose fibrils occurs in the elongation zone, while net random and longitudinal orientations are found in subsequent older parts of the differentiation zone. The position and the size of the transverse zone is related with root growth rate. In the shoot the net orientation of cellulose fibrils is transverse in the elongating apical part of the hypocotyl, and longitudinal in the fully elongated basal part. Leaf primordia and very young leaves have a transverse orientation. Throughout further development the leaf epidermis builds a very complex pattern of cells with a random orientation and cells with a transverse or a longitudinal orientation of the cellulose fibrils. The patterns of net cellulose orientation correlate well with the cylindrical growth of roots and shoots and with the typical planar growth of the leaf blade. On both the shoot and the root surface very specific patterns of cellulose orientation occur at sites of specific cell differentiation: trichome-socket cells complexes on the shoot and root hairs on the root. 相似文献
6.
Rates and patterns of evolution in partial sequences of five mitochondrial
genes (cytochrome b, ATPase 6, NADH dehydrogenase subunit 5, tRNA(Glu), and
the control region) were compared among taxa in the passerine bird genera
Fringilla and Carduelis. Rates of divergence do not vary significantly
among genes, even in comparisons with the control region. Rate variation
among lineages is significant only for the control region and NADH
dehydrogenase subunit 5, and patterns of variation are consistent with the
expectations of neutral theory. Base composition is biased in all genes but
is stationary among lineages, and there is evidence for directional
mutation pressure only in the control region. Despite these similarities,
patterns of substitution differ among genes, consistent with alternative
regimes of selective constraint. Rates of nonsynonymous substitution are
higher in NADH dehydrogenase subunit 5 than in other protein-coding genes,
and transitions exist in elevated proportions relative to transversions.
Transitions appear to accumulate linearly with time in tRNA(Glu), and
despite exhibiting the highest overall rate of divergence among species,
there are no transversional changes in this gene. Finally, for resolving
phylogenetic relationships among Fringilla taxa, the combined
protein-coding data are broadly similar to those of the control region in
terms of phylogenetic informativeness and statistical support.
相似文献
7.
8.
Goehring I Gerencser AA Schmidt S Brand MD Mulder H Nicholls DG 《The Journal of biological chemistry》2012,287(19):15706-15717
Oscillations in plasma membrane potential play a central role in glucose-induced insulin secretion from pancreatic β-cells and related insulinoma cell lines. We have employed a novel fluorescent plasma membrane potential (Δψ(p)) indicator in combination with indicators of cytoplasmic free Ca(2+) ([Ca(2+)](c)), mitochondrial membrane potential (Δψ(m)), matrix ATP concentration, and NAD(P)H fluorescence to investigate the role of mitochondria in the generation of plasma membrane potential oscillations in clonal INS-1 832/13 β-cells. Elevated glucose caused oscillations in plasma membrane potential and cytoplasmic free Ca(2+) concentration over the same concentration range required for insulin release, although considerable cell-to-cell heterogeneity was observed. Exogenous pyruvate was as effective as glucose in inducing oscillations, both in the presence and absence of 2.8 mM glucose. Increased glucose and pyruvate each produced a concentration-dependent mitochondrial hyperpolarization. The causal relationships between pairs of parameters (Δψ(p) and [Ca(2+)](c), Δψ(p) and NAD(P)H, matrix ATP and [Ca(2+)](c), and Δψ(m) and [Ca(2+)](c)) were investigated at single cell level. It is concluded that, in these β-cells, depolarizing oscillations in Δψ(p) are not initiated by mitochondrial bioenergetic changes. Instead, regardless of substrate, it appears that the mitochondria may simply be required to exceed a critical bioenergetic threshold to allow release of insulin. Once this threshold is exceeded, an autonomous Δψ(p) oscillatory mechanism is initiated. 相似文献
9.
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