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991.
R A Skidgel C D Bennett J W Schilling F L Tan D K Weerasinghe E G Erd?s 《Biochemical and biophysical research communications》1988,154(3):1323-1329
Human plasma carboxypeptidase N was purified to homogeneity and its active and inactive subunits were separated. By introducing a novel technique, both forms of the active subunit (Mr = 55,000 and Mr = 48,000) were isolated. N-terminal sequencing of the active subunit of human carboxypeptidase N revealed significant homology with the N-terminal sequence of bovine carboxypeptidase H (43% identity) and to a lesser extent with carboxypeptidase A (29% identity) or carboxypeptidase B (18% identity). The active subunit of carboxypeptidase N was hydrolyzed with trypsin and 4 of the tryptic peptides were isolated by HPLC and sequenced. The sequences of the four peptides were homologous (39-64% identity) with regions of carboxypeptidase H corresponding to the middle (residues 148-175) and C-terminal portion (residues 321-408). These regions had essentially no homology with carboxypeptidase A or B. These data indicate that carboxypeptidase H and the active subunit of carboxypeptidase N may have diverged from a common ancestral gene. 相似文献
992.
Isolation and characterization of three protein proteinase isoinhibitors from the granular fraction of horse neutrophilic granulocytes 总被引:3,自引:0,他引:3
A Pellegrini G H?geli R von Fellenberg 《Biochemical and biophysical research communications》1988,154(3):1107-1113
Three cathodically migrating protein protease isoinhibitors were isolated from the granule-rich fraction of equine neutrophilic granulocytes by means of FPLC chromatography, in addition to two previously described anodically migrating inhibitors. The three isoinhibitors had an identical enzyme specificity which was equal to the two previously described isoinhibitors; they inhibited exclusively proteinase K and subtilisin. The inhibitors retained their activity between pH 1 and 12. They also were heat stable at 100 degrees C for 20 min. Neither the biological function of isoinhibitors nor the fundamental role of granular protease inhibitors of such narrow and peculiar enzyme specificity are known. 相似文献
993.
Histochemical peculiarities on binding of castor-oil plant, soybean and lentil lectins with tissues of the mucous membrane in the stomach, small and large intestine have been studied in the human being, rat, mouse, as well as the lectins mentioned and the maize agglutinin with the nervous tissue of the rat cerebral tissue. The reactions are carried out with nonfixed cryostat and deparaffinized histological slices. Lectins labelled with horseradish peroxidase are used. Certain specific peculiarities and differences concerning the lectin binding with tissues of the organs studied are determined. Predominant binding is noted of the soybean lectin with parietal and mucin-producing cells of the stomach, with epitheliocytes of the duodenal glands, with the brush border of the epithelial cells of the intestinal villi. The lentil and castor-oil plant lectins make contours of the basal membrane epithelium in the stomach and intestine. The lentil lectin also reacts with the germinative centers of the stomach lymphatic nodules and the castor-oil plant agglutinin--with the brush border of the small intestine epitheliocytes. The lectins used are predominantly bound with neurons of the subcortical formations of the rat brain and cerebral cortex. By means of labelled lectins of lentil, soybean, and castor-oil plant it is possible to reveal certain modifications of the rat small intestine glycoconjugates produced by means of the immortelle extract. 相似文献
994.
Evidence for a differential physiological modulation of brown fat iodothyronine 5'-deiodinase activity in the perinatal period 总被引:1,自引:0,他引:1
M Giralt I Martin T Mampel F Villarroya R Iglesias O Vi?as 《Biochemical and biophysical research communications》1988,156(1):493-499
Brown adipose tissue iodothyronine 5'-deiodinase increases progressively in fetuses from the day 17 of pregnancy on, it reaches peak values on the 20th day of gestation and declines in the last days of fetal life as well as during the first day of life. Birth of premature fetuses causes a sudden drop in the enzyme activity. Postmaturity is associated to a decrease in brown fat 5'-deiodinase similar to that found after birth in fetuses born at term. In the first hours of life brown fat iodothyronine 5'-deiodinase is essentially insensitive to the cold-stimulus. Present data indicates that, differently from adult rats, brown fat iodothyronine 5'-deiodinase activity during the perinatal period is dissociated from the thermogenic activity of the tissue. It is suggested that factors different from the action of the sympathetic nervous system may play a main role in brown fat iodothyronine 5'-deiodinase activity modulation in the fetal and neonatal life. 相似文献
995.
Periodic cleavage of poly(dA) by oligothymidylates covalently linked to the 1,10-phenanthroline-copper complex 总被引:5,自引:0,他引:5
J C Fran?ois T Saison-Behmoaras M Chassignol N T Thuong J S Sun C Hélène 《Biochemistry》1988,27(7):2272-2276
1,10-Phenanthroline (OP) was covalently attached to the 3'-terminus of two oligothymidylates via different linkers [abbreviated as T8-(OP) and T6-(OP)]. In the presence of Cu2+ and 3-mercaptopropionic acid (MPA), these reagents induce a hybridization-dependent cleavage of poly(dA) and of a 27 nucleotide long oligodeoxynucleotide containing an A8 sequence. The principal cleavage sites on the 27-mer span four residues located near the 3'-terminal phosphate group of T8-(OP). When poly(dA) was degraded by T6-(OP) and T8-(OP), a series of bands were obtained corresponding to a repeat unit of six and eight nucleotides, respectively. This periodicity reflects the cooperative binding of oligothymidylate-OP to the polynucleotide matrix and the localized nicking sites. 相似文献
996.
Distinct tissue specific mitochondrial creatine kinases from chicken brain and striated muscle with a conserved CK framework 总被引:3,自引:0,他引:3
997.
M I Avelda?o 《Biochemistry》1988,27(4):1229-1239
About one-fourth the phosphatidylcholines (PCs) from bovine disk photoreceptor membranes contain very long chain (24-36 carbons) polyunsaturated (4, 5, and 6 double bonds) fatty acids of the n-3 and n-6 series (VLCPUFA). Such fatty acids, exclusively occurring in dipolyunsaturated species, are esterified to the sn-1 position of their glycerol backbone, docosahexaenoate being the major fatty acid at sn-2. Chromatographically, such PCs display a weakly polar character relative to other species, ascribable to their exceedingly large number of carbons. After hexane extraction of lyophilized disks, PC is the major component of the fraction of lipids that remains associated with rhodopsin, followed by phosphatidylserine, while a large proportion of the phosphatidylethanolamine is removed. The fatty acid composition of the hexane-removable and protein-bound lipid fractions markedly differs, the latter being enriched in lipid species containing long-chain and very long chain polyenes. This is observed for all lipid classes except free fatty acids. VLCPUFA-containing PCs are the most highly concentrated species in the rhodopsin-associated lipid fraction. The very long chain polyenes these PCs have at sn-1 may account for their resistance to being separated from the protein. It is hypothesized that their unusually long polyenoic fatty acids could be well suited to partially surround alpha-helical segments of rhodopsin. 相似文献
998.
Biochemistry of metallothionein 总被引:70,自引:0,他引:70
999.
Structure of phosphate-free ribonuclease A refined at 1.26 A 总被引:21,自引:0,他引:21
The structure of phosphate-free bovine ribonuclease A has been refined at 1.26-A resolution by a restrained least-squares procedure to a final R factor of 0.15. X-ray diffraction data were collected with an electronic position-sensitive detector. The final model consists of all atoms in the polypeptide chain including hydrogens, 188 water sites with full or partial occupancy, and a single molecule of 2-methyl-2-propanol. Thirteen side chains were modeled with two alternate conformations. Major changes to the active site include the addition of two waters in the phosphate-binding pocket, disordering of Gln-11, and tilting of the imidazole ring of His-119. The structure of the protein and of the associated solvent was extensively compared with three other high-resolution, refined structures of this enzyme. 相似文献
1000.
Class III human liver alcohol dehydrogenase: a novel structural type equidistantly related to the class I and class II enzymes 总被引:10,自引:0,他引:10
The primary structure of class III alcohol dehydrogenase (dimeric with chi subunits) from human liver has been determined by peptide analyses. The protein chain is a clearly distinct type of subunit distantly related to those of both human class I and class II alcohol dehydrogenases (with alpha, beta, gamma, and pi subunits, respectively). Disregarding a few gaps, residue differences in the chi protein chain with respect to beta 1 and pi occur at 139 and 140 positions, respectively. Compared to class I, the 373-residue chi structure has an extra residue, Cys after position 60, and two missing ones, the first two residues relative to class I, although the N-terminus is acetylated like that for those enzymes. The chi subunit contains two more tryptophan residues than the class I subunits, accounting for the increased absorbance at 280 nm. There are also four additional acidic and two fewer basic side chains than in the class I beta structure, compatible with the markedly different electrophoretic mobility of the class III enzyme. Residue differences between class III and the other classes occur with nearly equal frequency in the coenzyme-binding and catalytic domains. The similarity in the number of exchanges relative to that of the enzymes of the other two classes supports conclusions that the three classes of alcohol dehydrogenase reflect stages in the development of separate enzymes with distinct functional roles. In spite of the many exchanges, the residues critical to basic functional properties are either completely unchanged--all zinc ligands and space-restricted Gly residues--or partly unchanged--residues at the coenzyme-binding pocket.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献