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71.
72.
Cytosolic and mitochondrial isoenzymes of branched-chain amino acid aminotransferase during development of the rat. 下载免费PDF全文
The isoenzymic forms of branched-chain amino acid aminotransferase in mitochondria of rat tissues were compared with the better-known cytosolic forms in order to find any regular pattern of expression of these isoenzymes during development. Mitochondria of all tissues examined except brain contained only a type-I isoenzyme differing from the cytosolic type-I isoenzyme in heat stability and activation by mercaptoethanol. Foetal and adult brain mitochondria contained isoenzymes type III as well as type I. The large excess of type-I isoenzyme in foetal liver was localized in mitochondria, apparently of haematopoietic cells. The activity of this isoenzyme declined precipitously (by 80%) from day 19 of gestation at the same period and rate as does the volume fraction of haematopoietic cells that are then leaving the liver. Cortisol treatment accelerated the loss of these cells, and proportionally accelerated loss of the mitochondrial isoenzyme I. A development succession of type-I isoenzyme by the unique type II of liver parenchymal cell cytosols could not be demonstrated, since small, about equal, amounts of types I and II were always present in cytosols of foetal and adult liver. Developmental succession of isoenzymes within tissues was limited to cytosols and was demonstrated by the presence of cytosolic isoenzyme III in foetal and newborn skeletal muscle and kidney, organs which contain only isoenzyme I in the adult. 相似文献
73.
T Shiba T Akiyama T Kadowaki Y Fukami T Tsuji T Osawa M Kasuga F Takaku 《Biochemical and biophysical research communications》1986,135(3):720-727
The band 3 glycoprotein from human erythrocytes was found to be phosphorylated on tyrosine residues by the purified EGF receptor kinase and the purified src kinase in vitro. Kinetic analysis revealed that Km of the band 3 protein phosphorylation by the EGF receptor kinase was 0.17 microM and 0.65 microM in the absence and presence of EGF (3 X 10(-7)M), respectively, and that in the case of the src kinase it was 0.4 microM. From these data the band 3 protein can be regarded as one of the best substrates common for the EGF receptor kinase and the src kinase in vitro. 相似文献
74.
Chie L Chen JM Friedman FK Chung DL Amar S Michl J Yamaizumi Z Brandt-Rauf PW Pincus MR 《Journal of Protein Chemistry》1999,18(8):881-884
We have previously found that a peptide corresponding to residues 35–47 of the ras-p21 protein, from its switch 1 effector domain region, strongly inhibits oocyte maturation induced by oncogenic p21, but not by insulin-activated cellular wild-type p21. Another ras–p21 peptide corresponding to residues 96–110 that blocks ras–jun and jun kinase (JNK) interactions exhibits a similar pattern of inhibition. We have also found that c-raf strongly induces oocyte maturation and that dominant negative c-raf strongly blocks oncogenic p21-induced oocyte maturation. We now find that the p21 35–47, but not the 96–110, peptide completely blocks c-raf-induced maturation. This finding suggests that the 35–47 peptide blocks oncogenic ras at the level of raf; that activated normal and oncogenic ras–p21 have differing requirements for raf-dependent signaling; and that the two oncogenic-ras-selective inhibitory peptides, 35–47 and 96–110, act at two different critical downstream sites, the former at raf, the latter at JNK/jun, both of which are required for oncogenic ras-p21 signaling. 相似文献
75.
Chie Urashi Kosuke M. Teshima Sumiko Minobe Osamu Koizumi Nobuyuki Inomata 《Ecology and evolution》2013,3(7):2251-2261
Inference of genetic structure and demographic history is fundamental issue in evolutionary biology. We examined the levels and patterns of genetic variation of a widespread mangrove species in the Indo‐West Pacific region, Bruguiera gymnorrhiza, using ten nuclear gene regions. Genetic variation of individual populations covering its distribution range was low, but as the entire species it was comparable to other plant species. Genetic differentiation among the investigated populations was high. They could be divided into two genetic clusters: the West and East clusters of the Malay Peninsula. Our results indicated that these two genetic clusters derived from their ancestral population whose effective size of which was much larger compared to the two extant clusters. The point estimate of speciation time between B. gymnorrhiza and Bruguiera sexangula was two times older than that of divergence time between the two clusters. Migration from the West cluster to the East cluster was much higher than the opposite direction but both estimated migration rates were low. The past Sundaland and/or the present Malay Peninsula are likely to prevent gene flow between the West and East clusters and function as a geographical or land barrier. 相似文献
76.
Shuji Yonezawa Hidekuni Yamakawa Chie Muto Motoko Hosono Takahiko Yamamoto Kazunari Hattori Masahiro Sakagami Hiroko Togame Yoshikazu Tanaka Toru Nakano Hiroshi Takemoto Mitsuhiro Arisawa Satoshi Shuto 《Bioorganic & medicinal chemistry letters》2013,23(10):2912-2915
To improve the efficacy of the conformationally restricted BACE1 inhibitors, structural modifications were investigated using two strategies: (a) modification of the terminal aromatic ring and (b) insertion of a spacer between the aromatic rings. In the latter approach, another type of inhibitor 17 bearing an ethylene spacer between two aromatic rings was found to exhibit good BACE1 inhibitory activity, while the corresponding conformationally unrestricted compound 25 showed no activity. This result revealed an interesting effect of a conformational restriction with a cyclopropane ring. 相似文献
77.
The reactions of molecular oxygen (O2) and nitric oxide (NO) with reduced Thermus thermophilus (Tt) ba3 and bovine heart aa3 were investigated by time-resolved optical absorption spectroscopy to establish possible relationships between the structural diversity of these enzymes and their reaction dynamics. To determine whether the photodissociated carbon monoxide (CO) in the CO flow-flash experiment affects the ligand binding dynamics, we monitored the reactions in the absence and presence of CO using photolabile O2 and NO complexes. The binding of O2/NO to reduced ba3 in the absence of CO occurs with a second-order rate constant of 1 × 109 M? 1 s? 1. This rate is 10-times faster than for the mammalian enzyme, and which is attributed to structural differences in the ligand channels of the two enzymes. Moreover, the O2/NO binding in ba3 is 10-times slower in the presence of the photodissociated CO while the rates are the same for the bovine enzyme. This indicates that the photodissociated CO directly or indirectly impedes O2 and NO access to the active site in Tt ba3, and that traditional CO flow-flash experiments do not accurately reflect the O2 and NO binding kinetics in ba3. We suggest that in ba3 the binding of O2 (NO) to heme a32 + causes rapid dissociation of CO from CuB+ through steric or electronic effects or, alternatively, that the photodissociated CO does not bind to CuB+. These findings indicate that structural differences between Tt ba3 and the bovine aa3 enzyme are tightly linked to mechanistic differences in the functions of these enzymes. This article is part of a Special Issue entitled: Respiratory Oxidases. 相似文献
78.
Jaemin Lee Takeshi Yamamoto Shusaku Hayashi Hirofumi Kuramoto Makoto Kadowaki 《Biochemical and biophysical research communications》2013,430(3):895-900
Recent advances in neuroscience and immunology have revealed a bidirectional interaction between the nervous and immune systems. Therefore, the gastrointestinal tract may be modulated by neuro–immune interactions, but little information about this interaction is available. Intrinsic and extrinsic primary afferent neurons play an important role in this interaction because of their abilities to sense, process and transmit various information in the intestinal microenvironment. Calcitonin gene-related peptide (CGRP) is exclusively contained in intrinsic and extrinsic primary afferent neurons in the mouse intestine. Therefore, we investigated CGRP-immunoreactive nerve fibers in the colonic mucosa of mice induced to develop food allergy. CGRP-immunoreactive nerve fibers were specifically increased with the development of food allergy, and the fibers were juxtaposed to mucosal mast cells in the colonic mucosa of food allergy mice. Denervation of the extrinsic afferent neurons using neonatal capsaicin treatment did not affect the development of food allergy or the density and distribution of CGRP-immunoreactive nerve fibers in the colonic mucosa of food allergy mice. Furthermore, the mRNA and plasma level of CGRP was increased in food allergy mice. These results suggest that the activation of intrinsic primary afferent neurons in the intestine contributes to the development and pathology of food allergy. 相似文献
79.
80.
Nishimoto Y Zheng HY Zhong S Ikegaya H Chen Q Sugimoto C Kitamura T Yogo Y 《Journal of molecular evolution》2007,65(1):103-111
Similarly to other members of the Polyomaviridae family, BK virus (BKV) is thought to have co-evolved with its human host.
BKV has four subtypes that are distinguishable by immunological reactivity, with two (subtypes I and IV) being most prevalent
in human populations. Subtype I is the major subtype worldwide, whereas subtype IV is prevalent in East Asia and Europe but
rare in Africa. The geographic distribution pattern of subtype IV BKV is in apparent disagreement with the hypothesis that
BKV co-evolved with humans, since subtype IV rarely occurs in Africa. To elucidate the origin of subtype IV, 53 complete subtype
IV sequences derived from East Asians and Europeans were subjected to a detailed phylogenetic analysis using the maximum-likelihood
and neighbor-joining methods. We identified six subgroups (a1, a2, b1, b2, c1, and c2) that formed a tree represented by the
formula: “(a1, a2), ((b1, b2), (c1, c2)).” Interestingly, we found a close correlation between subtype IV subgroups and population
geography; thus, all subgroups except c2 were prevalent in particular East Asian populations, with c2 occurring in both Europe
and Northeast Asia. From these findings, we conclude that subtype IV of BKV now prevalent in modern humans is derived from
a virus that infected ancestral Asians. We introduce two hypotheses to explain how ancestral Asians became infected with subtype
IV BKV.
[Reviewing
Editor: Dr. Joshua Plotkin]
Yuriko Nishimoto and Huai-Ying Zheng are two authors contributed equally to this article. 相似文献