https://mmbr.asm.org/content/mmbr/47/3/410.full.pdf

Linkage map of Salmonella typhimurium, edition VII.

3-Isopropylmalate dehydrogenase (IPMDH, E.C. 1.1.1.85) from the thermophilic bacterium Thermus thermophilus HB8 is homologous to IPMDH from the mesophilic Escherichia coli, but has an approximately 17°C higher melting temperature. Its temperature optimum is 22–25°C higher than that of the E. coli enzyme; however, it is hardly active at room temperature. The increased conformational rigidity required to stabilize the thermophilic enzyme against heat denaturation might explain its different temperature-activity profile. Hydrogen/deuterium exchange studies were performed on this thermophilic-mesophilic enzyme pair to compare their conformational flexibilities. It was found that Th. thermophilus IPMDH is significantly more rigid at room temperature than E. coli IPMDH, whereas the enzymes have nearly identical flexibilities under their respective optimal working conditions, suggesting that evolutionary adaptation tends to maintain a “corresponding state” regarding conformational flexibility. These observations confirm that conformational fluctuations necessary for catalytic function are restricted at room temperature in the thermophilic enzyme, suggesting a close relationship between conformational flexibility and enzyme function.

https://www.pnas.org/content/pnas/95/13/7406.full.pdf

Adjustment of conformational flexibility is a key event in the thermal adaptation of proteins.

Candida lipolytica synthetisiert das Antibioticum Tryptanthrin aus 1 Mol Tryptophan und 1 Mol Anthranilsaure. Bei Verfutterung von Tryptophan und substituierter Anthranilsaure, bzw. substituiertem Tryptophan und Anthranilsaure, konnten die zu erwartenden Tryptanthrinderivate isoliert und identifiziert werden. Die Enzyme der Tryptanthrinbiosynthese wiesen in bezug auf diese Substrate, mit Ausnahme von Bromtryptophan, keine Spezifitat auf. Parallel zu diesen Versuchen wurden durch chemische Synthese substituierte Tryptanthrine hergestellt. Die Dierivate wurden auf ihre antibiotische Wirksamkeit gepruft; als besonders wirksam erwiesen sich die halogenierten Verbindungen.

Stoffwechselprodukte von Mikroorganismen

The copy number of 2 mu DNA-derived plasmids in CIR+ Saccharomyces cerevisiae transformants is determined by its selective marker and is usually much lower than that of the endogenous plasmid Only plasmids containing the leu2 allele of pJDB219, designated as leu2-d, under selective conditions displayed a higher copy number than did endogenous 2 mu DNA and by displacement generated cured cells Spontaneous loss of 2 mu DNA occurred with a frequency of about 002% per generation Curing plasmids, like pMP78, have copy numbers of 35; noncuring plasmids, like pDB248 or YEp6, have copy numbers of 4 to 8 The 2 mu DNA copy number in strains AH22 and YNN27 were determined to be 40 and 100, respectively The high copy number of leu2-d-containing plasmids can be explained by its weak expression of less than 5% that of the wild-type LEU2 gene The leu2-d allele has a deletion of the 5'-end sequence starting from 29 base pairs before the ATG initiation codon, but surprisingly, its expression is still regulated On YRp7, which contains the chromosomal autonomic replication sequence ARS1, the defective leu2-d allele could not complement a leu2 host strain This suggests a more stringent control of replication of ARS1-containing plasmids than of 2 mu-containing plasmids

The presence of a defective LEU2 gene on 2 mu DNA recombinant plasmids of Saccharomyces cerevisiae is responsible for curing and high copy number.

Metabolic engineering of Arabidopsis and Brassica for poly(3-hydroxybutyrate- 
co -3-hydroxyvalerate) copolymer production

Metabolic engineering of Arabidopsis and Brassica for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer production.

Threonine Deaminase from Salmonella typhimurium I. PURIFICATION AND PROPERTIES

The in vitro assembly of L-threonine deaminase from its constituent parts results in the formation of an inactive species of this enzyme which specifically and reversibly binds leucyl-tRNA. The native, catalytically active enzyme, which is derived from this species in the presence of maturation-inducing ligands, does not bind tRNA. The possible involvement of this protein-tRNA complex in the repression of the ilv (ADE) operon is discussed.

https://www.pnas.org/content/pnas/66/4/1027.full.pdf

Specific binding of leucyl transfer rna to an immature form of l-threonine deaminase: its implications in repression

http://www.jbc.org/content/243/1/186.full.pdf

R. O. Burns

Papers

Threonine Deaminase from Salmonella typhimurium I. PURIFICATION AND PROPERTIES

Specific binding of leucyl transfer rna to an immature form of l-threonine deaminase: its implications in repression

Threonine deaminase from Salmonella typhimurium. II. The subunit structure.

Threonine Deaminase from Salmonella typhimurium III. THE INTERMEDIATE SUBSTRUCTURE

Purification and Properties of β-Isopropylmalate Dehydrogenase