1.The uptake of 3Hp -aminobutyric acid by the retina.
Goodchild M;Neal MJ Br J Pharmacol. 1973 Mar;47(3):529-42.
1. The accumulation of (3)H-gamma-aminobutyric acid (GABA) by the isolated rat retina has been measured.2. When retinae were incubated at 37 degrees C in a medium containing (3)H-GABA, tissue:medium ratios of about 25:1 were attained after a 30 min incubation.3. After incubations of 40 min at 37 degrees C, almost all (98%) the radioactivity in the tissue was present as unchanged (3)H-GABA.4. The process responsible for (3)H-GABA uptake showed many of the properties of an active uptake system: it was temperature-sensitive, required the presence of sodium ions in the external medium, was inhibited by anoxia, dinitrophenol and ouabain, and showed saturation kinetics.5. The estimated Km value of GABA was 4.0 x 10(-5)M, and V(max) was 0.167 (mumoles/min)/g retina.6. The uptake of (3)H-GABA was not affected by the presence of large molar excesses of glycine, L-glutamate, L-aspartate, L-alanine, L-proline, or L-histidine, but was inhibited by DL-gamma-amino-beta-hydroxybutyrate, beta-guanidinopropionate, and L-2,4-diaminobutyrate.7. The retina was capable of achieving a large net uptake of GABA, indicating that the accumulation of (3)H-GABA by the tissue was not due only to an exchange process with the endogenous GABA pool.
2.Antitumour effect of L-2,4 diaminobutyric acid on a hepatoma cell line.
Blind PJ;Waldenström A;Berggren D;Ronquist G Anticancer Res. 2000 Nov-Dec;20(6B):4275-8.
Pharmacological treatment of malignant disease is often insufficient highlighting the need for more efficient treatment based on new principles. We have observed that the amino acid analogue diaminobutyric acid (DAB), accumulates in malignant cells apparently without saturation kinetics, leading to hyperosmosis and subsequently to cell lysis. In the first in vitro part of the present study hepatoma cells were incubated with DAB in miniwells in the presence or absence of physiological amino acids. In the in vivo part malignant cells were inoculated into rat liver after laparotomy. The tumour was treated by continuous infusion of DAB via a catheter, the tip of which was placed in the center of the tumour. DAB had a significant antitumour effect both in vitro and in vivo. The principle of action of DAB as an antitumour agent is unique and therefore would be the ideal partner to practically any other cytostatic drug for a combined treatment to achieve a synergistic effect.
3.Design of an ectoine-responsive AraC mutant and its application in metabolic engineering of ectoine biosynthesis.
Chen W;Zhang S;Jiang P;Yao J;He Y;Chen L;Gui X;Dong Z;Tang SY Metab Eng. 2015 Jul;30:149-155. doi: 10.1016/j.ymben.2015.05.004. Epub 2015 Jun 4.
Advanced high-throughput screening methods for small molecules may have important applications in the metabolic engineering of the biosynthetic pathways of these molecules. Ectoine is an excellent osmoprotectant that has been widely used in cosmetics. In this study, the Escherichia coli regulatory protein AraC was engineered to recognize ectoine as its non-natural effector and to activate transcription upon ectoine binding. As an endogenous reporter of ectoine, the mutated AraC protein was successfully incorporated into high-throughput screening of ectoine hyper-producing strains. The ectoine biosynthetic cluster from Halomonas elongata was cloned into E. coli. By engineering the rate-limiting enzyme L-2,4-diaminobutyric acid (DABA) aminotransferase (EctB), ectoine production and the specific activity of the EctB mutant were increased. Thus, these results demonstrated the effectiveness of engineering regulatory proteins into sensitive and rapid screening tools for small molecules and highlighted the importance and efficacy of directed evolution strategies applied to the engineering of genetic components for yield improvement in the biosynthesis of small molecules.
