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1.
We have previously shown that replacing the P1-site residue (Ala) of chicken ovomucoid domain 3 (OMCHI3) with a Met or Lys results in the acquisition of inhibitory activity toward chymotrypsin or trypsin, respectively. However, the inhibitory activities thus induced are not strong. In the present study, we introduced additional amino acid replacements around the reactive site to try to make the P1-site mutants more effective inhibitors of chymotrypsin or trypsin. The amino acid replacement Asp-->Tyr at the P2' site of OMCHI3(P1Met) resulted in conversion to a 35000-fold more effective inhibitor of chymotrypsin with an inhibitor constant (K(i)) of 1. 17x10(-11) M. The K(i) value of OMCHI3(P1Met, P2'Ala) indicated that the effect on the interaction with chymotrypsin of removing a negative charge from the P2' site was greater than that of introducing an aromatic ring. Similarly, enhanced inhibition of trypsin was observed when the Asp-->Tyr replacement was introduced into the P2' site of OMCHI3(P1Lys). Two additional replacements, Asp-->Ala at the P4 site and Arg-->Ala at the P3' site, made the mutant a more effective inhibitor of trypsin with a K(i) value of 1. 44x10(-9) M. By contrast, Arg-->Ala replacement at the P3' site of OMCHI3(P1Met, P2'Tyr) resulted in a greatly reduced inhibition of chymotrypsin, and Asp-->Ala replacement at the P4 site produced only a small change when compared with a natural variant of OMCHI3. These results clearly indicate that not only the P1-site residue but also the characteristics, particularly the electrostatic properties, of the amino acid residues around the reactive site of the protease inhibitor determine the strength of its interactions with proteases. Furthermore, amino acids with different characteristics are required around the reactive site for strong inhibition of chymotrypsin and trypsin. 相似文献
2.
Day-night changes in production of carbohydrate and protein by natural phytoplankton population from Lake Biwa, Japan 总被引:2,自引:0,他引:2
Hama Takeo; Matsunaga Katsuji; Handa Nobuhiko; Takahashi Mikio 《Journal of plankton research》1988,10(5):941-955
The 13C and gas chromatography-mass spectrometry (13C-GC-MS)method was applied to determine the day-night changes in thecomposition of photosynthetic products of the natural phytoplanktonpopulation from Lake Biwa, Japan. Glucose is the most abundantmonosaccharide in acid-hydrolyzable carbohydrate. The contributionof glucose was high in incubatesd samples in daytime and decreasedduring the night. Other monosaccharides (rhamnose, fucose, ribose,arabinose, xylose, mannose and galactose) and amino acids tendedto be produced throughout both day- and night-time. These resultssuggested that the carbon flows from glucose, which might constitutereserve glucan, to other monosaccharides and amino acids duringnight-time. The disproportionate production of glucose (reservedglucan) during daytime was thus partly cancelled out at night. 相似文献
3.
Role of Chitinase and Chitin Oligosaccharides in Lignification Response of Cultured Carrot Cells Treated with Mycelial Walls 总被引:3,自引:0,他引:3
Chitinase activity was induced in cultured carrot cells by incubationwith mycelial walls of a fungus, Chaetomium globosum. Both intra-and extracellular chitinases were resolved into four componentsby gel filtration chromatography. The extracellular enzymesliberated soluble oligosaccharides of different sizes from insolublechitin, suggesting that these carrot chitinases are endo-hydrolases.The solubilized chitinase digests obtained from insoluble mycelialwalls of C. globosum and chitin were fractionated by gel filtrationchromatography, and the elicitor activity of each fraction forthe accumulation of phenolic acids in cultured carrot cellswas determined. In both solubilized fragments of fungal wallsand of chitin, elicitor-active oligosaccharides were distributedin many fractions, however, potent activity for inducing phenolicacid synthesis was observed in the high molecular weight fractions. (Received October 5, 1987; Accepted February 12, 1988) 相似文献
4.
5.
Nobuhiko Ohga 《Ecological Research》1992,7(3):341-353
Herbaceous lomas in the Peruvian coastal desert, of South America establish in spring, and its habitat is limited to the southern
or southwestern slopes along the coast that are affected by thick fog. The time of appearance, the duration and the thickness
of the fog vary greatly from year to year, so the lomas can grow only in habitats with enough water to, sustain seed germination
and plant growth. This paper studies the species composition and density of the buried seed population, of the herbaceous
lomas of Loma Ancon in order to clarify the mechanisms of the lomas' establishment. The mean number of species with viable
seeds was about, 12 spp. m−2 and that of dead seeds was about 22 spp. m−2. The dominant species wereSolanum tuberiferum, S. pinnatifidum andNolana humifusa, both in viable and dead seeds. Viable seed density was about 5000–8000 seeds m−2, which is comparable with the seed densities of other herbaceous communities. Dead seed density was about 15000–27000 seeds
m−2, or nearly three times the viable seed density, because the rate of decomposition was slow in the extremely dry conditions.
The net increase of viable seeds by seed production was estimated at about 5000 seeds m−2 in 1980, and the increase in the number of dead seeds was 2200 seeds m−2. 相似文献
6.
Synopsis We tested the reactions of free embryos of the amphidromous goby, Rhinogobius brunneus, to light under both artificial and ambient conditions along streams in which their downstream migration occurs. The embryos showed a positive phototaxis to 500 1ux light but a negative response to light of more than 5000 lux. They were able to swim at 1.54 cm sec–1 t in still water and showed positive rheotaxis, but their swimming ability was not sufficient to allow active movement in rapids. Ambient natural light conditions varied among locations in relation to local topographical features. The variation in the diel periodicity of their migration could be explained by the interaction between behavioral reactions of embryos and environmental factors along river courses. 相似文献
7.
Kaoru Miyazaki Keisuke Mashima Nobuhiko Yamashita Jinpei Yamashita Takekazu Horio 《In vitro cellular & developmental biology. Plant》1985,21(1):62-66
Summary We have previously reported the transformation by Rous sarcoma virus of a cloned epithelial cell line (BRL) established from
Buffalo rat liver by H. Coon. The nontransformed (BRL) and transformed (RSV-BRL) cells grew at comparable rates in culture,
whereas only the transformed cells were tumorigenic in vivo. We report here on the existence in rat and mouse sera of a growth
inhibitor for the nontransformed BRL cells. The transformed BRL cells (RSV-BRL) were insensitive to this inhibitor. The inhibitory
activity was not prominent in sera from other species of animals tested except for rabbit; this serum inhibited the growth
of RSV-BRL cells more strongly than that of BRL cells. The growth inhibitor was partially purified from rat serum. It is a
protein free of lipid and has a molecular weight of about 220 000. The inhibitor could be separated into three components
of pI 4.6, 5.2 (major) and 5.6 by isoelectric electrophoresis.
EDITOR'S STATEMENT Although compelling theoretical arguments sometimes can be made for the likely existence of growth-inhibitory
substances of physical relevance in the control of cell proliferation, experiments aimed at identifying and studying such
factors often are difficult to design and interpret, and little strong data exists to suggest that growth-inhibitory substances
are important regulatorsin vivo. The information presented in this paper represents a start toward developing a useful system for studying growth-inhibitory
factor. David W. Barnes 相似文献
8.
Nobuhiko Saitô 《Cell biochemistry and biophysics》1987,11(1):321-329
The metling behavior of DNA and formation of α-helices and β-strands in protein can be discussed rigorously by statistical mechanical treatment. To do this, however, appropriate formulations are required for fast computer calculation. New formalisms for DNA and protein in terms of recurrence relations suitable for computer calculation are presented. 相似文献
9.
10.
Summary Polypeptides, synthesized from a mixture of amino acid amides by microwave heating during repeated hydration-dehydration cycles, showed hydrolase- and oxidoreductase-like catalytic activities. Poly(GAVDH), polypeptides synthesized from an equimolar mixture (each 0.1 M) of glycinamide,l-alaninamide,l-valinamide,l-aspartic acid -amide, andl-histidinamide, catalyzed the hydrolysis of PNPAc. The hydrolytic rate of PNPAc with poly(GAVDH) was the quadruple of that ofl-histidine alone. Though the kcat values of different resulting polypeptides were 103–106 times less than those of native hydrolases, the Km value of the polypeptides further containing phenylalanine residues was nearly equal to that of the esterase. This result indicates the presence of hydrophobic interaction between a substrate and the polypeptides. Resulting polypeptides also showed catalytic activity for the reduction of ferricyanide ion [Fe(CN)3–] with NADH. The polypeptides seemed to have a strong affinity for adenine nucleotides, because the reaction was inhibited by adenine derivatives such as NAD+ and AppA. A hypothesis for the emergence of primitive protein enzymes is discussed. 相似文献