全文获取类型
收费全文 | 78篇 |
免费 | 10篇 |
出版年
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 2篇 |
2012年 | 9篇 |
2011年 | 2篇 |
2010年 | 7篇 |
2009年 | 1篇 |
2008年 | 5篇 |
2007年 | 6篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1994年 | 1篇 |
1991年 | 2篇 |
1990年 | 7篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有88条查询结果,搜索用时 15 毫秒
81.
82.
Localization of the lysine epsilon-aminotransferase (lat) and delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase (pcbAB) genes from Streptomyces clavuligerus and production of lysine epsilon-aminotransferase activity in Escherichia coli. 总被引:2,自引:1,他引:1
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
M B Tobin S Kovacevic K Madduri J A Hoskins P L Skatrud L C Vining C Stuttard J R Miller 《Journal of bacteriology》1991,173(19):6223-6229
Lysine epsilon-aminotransferase (LAT) in the beta-lactam-producing actinomycetes is considered to be the first step in the antibiotic biosynthetic pathway. Cloning of restriction fragments from Streptomyces clavuligerus, a beta-lactam producer, into Streptomyces lividans, a nonproducer that lacks LAT activity, led to the production of LAT in the host. DNA sequencing of restriction fragments containing the putative lat gene revealed a single open reading frame encoding a polypeptide with an approximately Mr 49,000. Expression of this coding sequence in Escherichia coli led to the production of LAT activity. Hence, LAT activity in S. clavuligerus is derived from a single polypeptide. A second open reading frame began immediately downstream from lat. Comparison of this partial sequence with the sequences of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D valine (ACV) synthetases from Penicillium chrysogenum and Cephalosporium acremonium and with nonribosomal peptide synthetases (gramicidin S and tyrocidine synthetases) found similarities among the open reading frames. Since mapping of the putative N and C termini of S. clavuligerus pcbAB suggests that the coding region occupies approximately 12 kbp and codes for a polypeptide related in size to the fungal ACV synthetases, the molecular characterization of the beta-lactam biosynthetic cluster between pcbC and cefE (approximately 25 kbp) is nearly complete. 相似文献
83.
Matthew B. Tobin Stephen C.J. Cole Steven Kovacevic James R. Miller Jack E. Baldwin John D. Sutherland 《FEMS microbiology letters》1994,121(1):39-46
Abstract Using a high level Escherichia coli expression system for the Penicillium chrysogenum penDE gene, we have produced acyl-coenzyme A: isopenicillin N acyltransferase (AT) enzymes containing amino acid substitutions at three conserved Ser residues. Chosen for study based on amino acid sequence homologies to other proteins, Ser227 , Ser230 and Ser309 were changed to Cys or Ala to assess amino acid side chain involvement in proenzyme cleavage and AT enzyme mechanism. Substitutions at Ser230 had no effect on proenzyme cleavage, acyl-coenzyme A: IPN acyltransferase (IAT) or acyl-coenzyme A: 6-aminopenicillanic acid acyltransferase (AAT) activities. While Ser227 →Cys had no effect, Ser227 →Ala produced uncleaved proenzyme lacking both AAT and IAT activities, suggesting that the presence of a nucleophilic side chain at this residue is required for proenzyme cleavage and AT activity. Substitution of Ser309 →Cys did not appreciably prevent proenzyme cleavage, IAT or AAT activity. Recombinant AT (recAT) proenzyme containing Ser309 →Ala was cleaved; however, IAT and AAT activities were not observed. This separation of proenzyme cleavage from IAT and AAT activities has not been previously observed, and suggests that Ser309 is involved in substrate acylation. 相似文献
84.
85.
86.
87.
88.
M Ravazzola D Baetens R Engerman N Kovacevic M Vranic L Orci 《Hormones et métabolisme》1977,9(6):480-483
Immunofluorescence shows that the oxyntic mucosa of a dog depancreatized for 5 years and having a poorly-controlled diabetes has more glucagon- and somatostatin-containing cells than the mucosa of a control dog. At the ultrastructural level, 4 endocrine cell types are identified: A-, A-like, D- and enterochromaffin-like (ECL) cells, with increased numbers of A-, A-like and D-cells in gastric glands of the depancreatized dog, together with a higher concentration of immunoreactive glucagon in the gastric mucosa. The increase in A-, A-like and D-cells is compatible with: a) a change induced by the diabetic state itself; b) a hyperplasia secondary to the loss of corresponding pancreatic cells. At any rate, the fact that A-, A-like and D-cells increase parallely may indicate that these three cell types are functionally related one with another. 相似文献