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101.
Yvonne H. Edwards Sue Povey Kay M. Levan Catherine E. Driscoll Jose Luis Millan Erwin Goldberg 《Genesis (New York, N.Y. : 2000)》1987,8(4):219-232
From the data presented in this report, the human LDHC gene locus is assigned to chromosome 11. Three genes determine lactate dehydrogenase (LDH) in man. LDHA and LDHB are expressed in most somatic tissues, while expression of LDHC is confined to the germinal epithelium of the testes. A human LDHC cDNA clone was used as a probe to analyze genomic DNA from rodent/human somatic cell hybrids. The pattern of bands with LDHC hybridization is easily distinguished from the pattern detected by LDHA hybridization, and the LDHC probe is specific for testis mRNA. The structural gene LDHA has been previously assigned to human chromosome 11, while LDHB maps to chromosome 12. Studies of pigeon LDH have shown tight linkage between LDHB and LDHC leading to the expectation that these genes would be syntenic in man. However, the data presented in this paper show conclusively that LDHC is syntenic with LDHA on human chromosome 11. The terminology for LDH genes LDHA, LDHB, and LDHC is equivalent to Ldhl, Ldh2, and Ldh3, respectively. 相似文献
102.
Out of the eight enzymes involved in the biosynthesis of the isoquinoline alkaloid berberine, at least, two enzymes, berberine bridge enzyme and (S)-tetrahydroprotoberberine oxidase, are exclusively located in a vesicle with a specific gravity of =1.14 g·cm–3 as shown by direct enzymatic assay as well as immunoelectrophoresis. Electronmicroscopic examination of the enzyme-containing particulate preparation from Berberis wilsoniae var. subcaulialata cultured cells demonstrated that it is composed mainly of membranous vesicles. The protein composition of this preparation reveals the presence of only about 20 separable proteins, of which two major ones are berberine bridge enzyme and (S)-tetrahydroprotoberberine oxidase. Incubation of these vesicles with the substrate (S)-reticuline in the presence and absence of S-adenosyl-l-methionine leads to the formation of a red product which was identified as dehydroscoulerine. If the cytoplasmic enzyme S-adenosyl-l-methionine:(S)-scoulerine-9-O-methyltransferase is added to the vesicle preparation in the presence of (S)-reticuline and S-adenosyl-l-methionine, not dehydroscoulerine but columbamine, the immediate precursor of berberine is formed. Some of the quaternary alkaloids are located inside the vesicles; fusion of these vesicles leads to vacuoles containing the quaternary alkaloids. These vesicles are the first highly specific and unique compartment serving only alkaloid biosynthesis; they are found in members of four different plant families and in cell cultures as well as in differentiated tissue.Abbreviations BBE
berberine bridge enzyme
- STOX
(S)-tetrahydroprotoberberine oxidase
Dedicated to Professor Karl Decker, Freiburg, on the occasion of his 60th birthday 相似文献
103.
Dipple Anthony Pigott Margaret A. Milner John A. 《Biological trace element research》1986,10(2):153-157
Since selenium has been found to exert a protective action against carcinogenesis in various systems, the mechanism where-by
sodium selenite inhibits DNA binding of the carcinogen, 7,12-dimethylbenz[a]anthracene, was investigated. It was found that
selenite preferentially reduced DNA binding occurring through ananti-dihydrodiol epoxide metabolite of this carcinogen by inhibiting the induction of an enzyme system that generates this specific
reactive metabolite. 相似文献
104.
Immunoaffinity purified Sm/RNP antigens from buffalo and goat liver were studied to determine the role of RNA and proteins
towards the antigenicity of Sm and RNP antigens. A more direct approach using enzyme-linked immunosorbent assay on nylon beads
has been utilized to look into the problem. The effect of enzyme treatment and the role of RNA and protein fractions in influencing
antigenicity have been described. RNA seems to be involved in the maintenance of RNP specific polypeptides in suitable conformation
so as to keep them in solution. Removal of RNA leads to insolubilization of RNP specific polypeptides. Antibodies to Sm and
RNP antigens have been shown to cross react with poly A containing heterogeneous nuclear ribonucleoprotein with no cross reactivity
with thymus RNA or DNA. 相似文献
105.
The lysosomal enzyme binding protein (receptor protein) isolated from monkey brain was immobilised on Sepharose 4B and used
to study the binding of brain lysosomal enzymes. The immobilised protein could bind \-D-glucosaminidase, α-D-mannosidase,
α-L-fucosidase and2-D-glucuronidase. The bound enzymes could be eluted either at an acid pH of 4.5 or by mannose 6-phosphate
but not by a number of other sugars tested. Binding could be abolished by prior treatment of the lysosomal enzymes with sodium
periodate. Alkaline phosphatase treatment of the enzymes did not prevent the binding of the lysosomal enzymes to the column
but decreased their affinity, as seen by a shift in their elution profile, when a gradient elution with mannose 6-phosphate
was employed. These results suggested that an ‘uncovered’ phosphate on the carbohydrate moiety of the enzymes was not essential
for binding but can enhance the binding affinity. 相似文献
106.
Sadaaki Iwanaga Takashi Morita Toshiyuki Miyata Takanori Nakamura Jun Aketagawa 《Journal of Protein Chemistry》1986,5(4):255-268
A hemocyte lysate from horseshoe crab produced a gel, when exposed to Gram-negative bacterial endotoxins. This gelation reaction of the lysate, so-called Limulus test, has been widely employed as a simple and very sensitive assay method for endotoxins. Recent biochemical studies on the principle of Limulus test indicate that the hemocytes contain several serine protease zymogens, which constitute a coagulation cascade triggered by endotoxins, and that there is a (1 3)--d-glucan-mediated coagulation pathway which also results in the formation of gel. Up to now, six protein components, designated coagulogen, proclotting enzyme, factor B, factor C, factor G and anti-LPS factor, all of which are closely associated with the endotoxin-mediated coagulation pathway, have been purified and biochemically characterized. Among these components, the complete amino acid sequences of coagulogens isolated from one American and three Asian species of horseshoe crabs have been established. Moreover, the reconstitution experiment using the isolated clotting factors, C, B, proclotting enzyme and coagulogen in the presence of endotoxin, leads to the formation of coagulin get. Based on these results, we propose here a mechanism for the Limulus coagulation cascade. 相似文献
107.
Multiple conformations of amino acid residues in ribonuclease A 总被引:1,自引:0,他引:1
L. Anders Svensson Lennart Sjlin Gary L. Gilliland Barry C. Finzel Alexander Wlodawer 《Proteins》1986,1(4):370-375
The highly refined 1.26 A structure (R = 0.15) of phosphate-free bovine pancreatic ribonuclease A was modeled with 13 residues having discrete multiple conformations of side chains. These residues are widely distributed over the protein surface, but only one of them, Lys 61, is involved in crystal packing interactions. The discrete conformers have no unusual torsion angles, and their interactions with the solvent and with other atoms of the protein are similar to those residues modeled with a single conformation. For three of the residues--Val 43, Asp 83, and Arg 85--two correlated conformations are found. The observed multiple conformations on the protein surfaces will be of significance in analyzing structure-function relationships and in performing protein engineering. 相似文献
108.
Proteins and peptides in water-restricted environments 总被引:5,自引:0,他引:5
M Waks 《Proteins》1986,1(1):4-15
109.
The gibberellin (GA) 2-hydroxylases in mature and immature seeds of Pisum sativum have been partially purified and characterised. The enzymes are unstable when stored below pH 7.0 or in the absence of a thiol reagent. The optimum assay pH is between 7.4 and 7.8 and activity is dependent upon the presence of -ketoglutarate, Fe2+ and ascorbate. The 2-hydroxylase activities for GA1, GA4, GA9 and GA20 are chromatographically inseparable and correspond to a protein of Mr 44000. The rate of GA 2-hydroxylation varies according to substrate and some evidence indicates that the 2-hydroxylase activities for GA1 and GA4 and for GA9 and GA20 may reside in different proteins. During pea seed maturation, the specific activity of the enzyme(s) increases dramatically and reaches a maximum at a time when endogenous GA9, GA20, GA29 and GA51 are also at their greatest concentration. This correlation is not the result of substrate induction of enzyme activity. Since the GA 2-hydroxylases operate at maximal rate at low substrate concentrations they are incapable of rapidly 2-hydroxylating excessive quantities of (exogenously applied) GA1 or GA20. On the basis of the kinetic parameters of the GA 2-hydroxylase activities, a generalised model is discussed for the control of the steady-state levels of bioactive hormone under normal physiological conditions.Abbreviations DTE
dithioerythritol
- EDTA
ethylenediaminetetraacetic acid
- GAn
gibberellin An
- HPLC
high-performance liquid chromatography
- HSS
high-speed supernatant
- LSS
low-speed supernatant
- PMSF
phenylmethane sulphonyl fluoride 相似文献
110.
A mouse model for the "sudden death" and "malarial lung" syndromes is described. Mice of the C3H/z strain succumb suddenly approximately 7 days after an infection with Plasmodium berghei becomes patent, at a time when parasitemia is still moderate (6 to 8%). Death could be shown to be due to anaphylactoid shock, probably induced by soluble immune complexes. Increased vascular permeability caused transudation and leakage of serum proteins into the interstitium and the alveoli. The lungs were found to be edematous, with a fine granular precipitate in the alveoli and adherent to the vascular walls. The precipitates reacted with antiglobulins G and M, and could be shown to also contain malaria antigens and C3/4. A dramatic drop in hematocrit was recorded several hours before death, indicating the sudden release of malaria antigens. The myocardium of animals that had died very suddenly showed a patchy loss of phosphorylase activity. This loss of activity was much more extensive, and sometimes almost total, when there had been an agonal period of several (1 to 3) hours before death. In these cases the irreversibility of the myocardial damage was also indicated by the loss of activity of the dehydrogenases, as well as by typical inflammatory reactions of granulocytic and histiocytic infiltrations. The hearts thus presented a typical picture of the acute and peracute shock syndromes. In acute shock cardiac insufficiency develops so suddenly that death ensues before irreversible damage has occurred, and cardiac insufficiency can only be demonstrated by the most sensitive of enzyme histochemical means. In the present case shock was induced by the anaphylactoid activity of immune complexes with the lung as target organ. The described syndrome appears analogous to human "malarial lung." 相似文献