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1.
2.
Jaroslav Dršata Martin Beránek VladimÍr Palička 《Journal of enzyme inhibition and medicinal chemistry》2013,28(1):31-36
Incubation of 50 mM d -glucose with aspartate aminotransferase (AST, EC 2.6.1.1) preparations (purified pig heart enzyme or a rat liver 20,000 × g supernatant) at 25°C had no effect on enzyme activity. 50 mM d -fructose or d -ribose gradually inhibited pig heart AST under the same conditions to zero activity after 14 days. 50 mM dl -glyceraldehyde decreased enzyme activity to zero after 6 days of incubation. The inhibition of pig heart AST by 50 mM d -fructose or d -ribose was marked even at a temperature of 4°C but it was less pronounced than at 25°C. There was no effect of 0.5 mM 2-oxoglutarate on AST activity during incubation, while the presence of 25 mM l -aspartate decreased it rapidly. 0.5 mM 2-oxoglutarate partly prevented inhibition of AST by d -ribose or d -fructose, while an analogous experiment with 25 mM aspartate resulted in a rapid decline similar to that in the absence of sugars. 相似文献
3.
Summary Two siblings with a short-limb dwarfing condition which we call acromesomelic dysplasia, Hunter-Thompson type are reported. Abnormalities are limited to the limbs and limb joints in this severe form of dwarfism. The middle and distal
segments of the limbs are most affected. The lower limbs are more affected than the upper. We are aware of one previously
published case of this entity reported by A. G. W. Hunter and M. W. Thompson in 1976. Dislocations of the elbows and ankles
were present in all three patients and dislocations of the hips and knees in two. One of the siblings who did not have hip
and knee dislocations clinically resembled Grebe chondrodysplasia, another severe acromesomelic dwarfing condition. However,
radiological analysis suggests that while acromesomelic dysplasia, Hunter-Thompson type and Grebe chondrodysplasia are related,
they are not identical. Grebe chondrodysplasia has been established as an autosomal recessive trait. It appears probable that
the entity we describe has the same mode of genetic transmission. 相似文献
4.
Hana Votavová Vladimír Gut Karel Bláha Jaroslav Šponar 《International journal of biological macromolecules》1982,4(6):341-346
DNA complexes with polypeptides (Lys-Ala-Ala)1)] and (Lys-Ala-Ala)34 have been studied using the methods of thermal melting and circular dichroism. Derivative melting curves of (Lys-Ala-Ala)10 DNA differed substantially from those of (Lys-Ala-Ala)34 prepared either by salt gradient dialysis or by direct mixing. Melting curves of the former complex were unimodal or bimodal with Tm increasing continuously withn input lysin-to-DNA phosphate ratio (r); those of the latter complex consisted of three separate transitions with Tm values almost independent of r. Complete reversibility of binding in the (Lys-Ala-Ala)10-DNA system but a slow redistribution of (Lys-Ala-Ala)34 on DNA at low temperature were found in the redistribution experiments Much faster redistribution from denatured to native DNA occurs at the temperature of melting, contributing to the unusual trimodal melting pattern. Circular dichroism curves are very similar for both complexes and indicate little change of DNA conformation upon polypeptide binding. 相似文献
5.
6.
Jaroslav Votruba Jarmila Pazlarová Milada Dvořáková Kalju Vanatalu Libuše Váchová Marie Strnadová Helena Kučerová Jiří Chaloupka 《Applied microbiology and biotechnology》1987,26(4):373-377
Summary A mathematical model was formulated to describe the kinetics and stoichiometry of growth and proteinase production in Bacillus megaterium. Synthesis of the extracellular proteinase in a batch culture is repressed by amino acids. The specific rate of formation of the enzyme (r
E) can be described by the formula {ie373-1}, where k
2 and k
3 stand for the non-repressible and repressible part of enzyme synthesis respectively, k
S
2 is a repression coefficient and S
2 indicates the concentration of amono acids; the values of k
2 and k
S
2 depend on the composition of the mixture of amino acids. Even in a high concentration, a single amino acid is less effective than a mixture of amino acids. The dependence of the proteinase repression on the concentration of an external amino acid (leucine) follows the same course as its rate of incorporation into proteins, approaching saturation at concentrations higher than 50 M (half saturation approximately 10 M). However, the total uptake of leucine did not exhibit any saturation even at 500 M external concentration.Symbols
X
biomass concentration, g/l
-
E
proteinase concentration, unit/l
-
t
time, h
-
S
1
concentration of glucose, g/l
-
S
2
concentration of amino acids, g/l
-
specific growth rate, l/h
-
rE
specific rate of enzyme production, unit/g/h
-
k
1
growth kinetic constant, l/h
-
k
2
product formation kinetic constant (for non-repressible part of enzyme synthesis), unit/g
-
k
3
product formation kinetic constant (for repressible portion of enzyme synthesis), unit/g
-
k
S
1
saturation constant, g/l
-
k
S
2
repression coefficient for a certain amino acid or amino acids mixture, g/l 相似文献
7.
Rat ovarian membrane LH/hCG receptor was solubilized in various detergents and reconstituted into proteoliposomes. Upon removal of sodium cholate by active absorption on Bio-Beads SM-2, the functional interaction between receptor and adenylate cyclase was restored. Adenylate cyclase was stimulated by hCG, HCG+GTP or GppNHp and NaF. Reconstituted proteoliposomes bound more 125I-hCG (528 fmol/mg protein) than membrane-bound receptors (384 fmol/mg protein). There was no difference, however, in the relative affinity of reconstituted receptor preparations for hCG. 相似文献
8.
Karel Indrak Vaclav Brabec Jarmila Indrakova Ladislav Chrobak Adriana Sakalova Marie Jarosova Jaroslav Cermak You-jun Fei Ferdane Kutlar Yuan-chao Gu Erol Baysal Titus H. J. Huisman 《Human genetics》1992,88(4):399-404
Summary We have identified different -thalassemia mutations in 93 members of 34 families of Czech or Slovakian descent using gene amplification, hybridization with specific 32P-labeled oligonucleotide probes, sequencing of amplified DNA, and gene mapping. The GA mutation at IVS-I-1 was found in 18 families; other Mediterranean mutations were IVS-II-1 (GA), IVS-II-745 (CG), IVS-I-110 (GA), and codon 39 (CT); these were present in 9 additional families. The GT mutation at codon 121, known to cause Heinzbody -thalassemia, was present in 3 families, and the frameshift at codons 82/83 (-G), first described in the Azerbaijanian population, in 2 families. A newly discovered allele was a frameshift at codons 38/39 (-C). One -thalassemia allele was incompletely characterized. We observed in 2 families a TC mutation at position +96 UTR (untranslated region) relative to the termination codon; this mutation likely is a rare polymorphism, -Thalassemia was rare; only one person carried the -3.7 heterozygosity, and one other had a yet to be identified -thalassemia-1, while seven had the anti 3.7 triplication. 相似文献
9.
Critical notes on the monograph “Phylogeny of the Nautiloidea” by J. Dzik (1984), especially with respect to cephalopod material from the Lower Palaeozoic of Bohemia are presented. Oncocerid type of muscle scars in the Lower Devonian genusPtenoceras as well as succession of growth stages of the shell in Silurian genusSphooceras is figured. 相似文献
10.
Covalent modification of phenylalanyl-tRNA synthetase with phenylalanine during the amino acid activation reaction catalyzed by the enzyme 总被引:3,自引:0,他引:3
E Rapaport G Yogeeswaran P C Zamecnik P Remy 《The Journal of biological chemistry》1985,260(17):9509-9512
Yeast phenylalanyl-tRNA synthetase (PRS) is shown to undergo autoaminoacylation with phenylalanine under in vitro amino acid activation conditions. Phenylalanyl adenylate enzyme complex yields a covalent phenylalanyl isopeptide exclusively with the beta subunit of the alpha 2 beta 2 enzyme. Contrary to previously reported cases of autoaminoacylation of aspartyl-tRNA synthetase and tryptophanyl-tRNA synthetase, the autoaminoacylation of PRS occurs under a specific set of conditions and results in the identification of only one labeled tryptic peptide on two types of high pressure liquid chromatography columns. The ability of PRS to undergo this covalent modification directly correlates with its ability to catalyze the synthesis of diadenosine 5',5"'-P1,P4-tetraphosphate from enzyme-bound phenylalanyl adenylate. Both reactions require the presence of low levels of zinc or cadmium and are inhibited by tRNAPhe or by low levels of low molecular weight thiols. Since diadenosine 5',5"'-P1,P4-tetraphosphate synthesis is known to be catalyzed in vivo in response to oxidation stress, it is also likely that the autoaminoacylation of phenylalanyl-tRNA synthetase may occur in vivo under a similar set of conditions. These reactions are thus not simply the result of accumulation of phenylalanyl adenylate and probably reflect conformational changes in the protein which are brought about by its interaction with zinc or cadmium. 相似文献