Expression of bacterial cysteine biosynthesis genes in transgenic mice and sheep: toward a newin vivo amino acid biosynthesis pathway and improved wool growth

1995 ◽  
Vol 4 (2) ◽  
pp. 87-104 ◽  
Author(s):  
C. S. Bawden ◽  
A. V. Sivaprasad ◽  
P. J. Verma ◽  
S. K. Walker ◽  
G. E. Rogers

2012 ◽  
Vol 78 (23) ◽  
pp. 8421-8430 ◽  
Author(s):  
Christian Weber ◽  
Christine Brückner ◽  
Sheila Weinreb ◽  
Claudia Lehr ◽  
Christine Essl ◽  
...  

ABSTRACTAdipic acid is a high-value compound used primarily as a precursor for the synthesis of nylon, coatings, and plastics. Today it is produced mainly in chemical processes from petrochemicals like benzene. Because of the strong environmental impact of the production processes and the dependence on fossil resources, biotechnological production processes would provide an interesting alternative. Here we describe the first engineeredSaccharomyces cerevisiaestrain expressing a heterologous biosynthetic pathway converting the intermediate 3-dehydroshikimate of the aromatic amino acid biosynthesis pathway via protocatechuic acid and catechol intocis,cis-muconic acid, which can be chemically dehydrogenated to adipic acid. The pathway consists of three heterologous microbial enzymes, 3-dehydroshikimate dehydratase, protocatechuic acid decarboxylase composed of three different subunits, and catechol 1,2-dioxygenase. For each heterologous reaction step, we analyzed several potential candidates for their expression and activity in yeast to compose a functionalcis,cis-muconic acid synthesis pathway. Carbon flow into the heterologous pathway was optimized by increasing the flux through selected steps of the common aromatic amino acid biosynthesis pathway and by blocking the conversion of 3-dehydroshikimate into shikimate. The recombinant yeast cells finally produced about 1.56 mg/litercis,cis-muconic acid.





2008 ◽  
Vol 21 (9) ◽  
pp. 1232-1241 ◽  
Author(s):  
Maria de las Nieves Peltzer ◽  
Nicolas Roques ◽  
Véréna Poinsot ◽  
O. Mario Aguilar ◽  
Jacques Batut ◽  
...  

Some Sinorhizobium meliloti mutants in genes involved in isoleucine, valine, and leucine biosynthesis were previously described as being unable to induce nodule formation on host plants. Here, we present a reappraisal of the interconnection between the branched-chain amino acid biosynthesis pathway and the nodulation process in S. meliloti. We characterized the symbiotic phenotype of seven mutants that are auxotrophic for isoleucine, valine, or leucine in two closely related S. meliloti strains, 1021 and 2011. We showed that all mutants were similarly impaired for nodulation and infection of the Medicago sativa host plant. In most cases, the nodulation phenotype was fully restored by the addition of the missing amino acids to the plant growth medium. This strongly suggests that auxotrophy is the cause of the nodulation defect of these mutants. However, we confirmed previous findings that ilvC and ilvD2 mutants in the S. meliloti 1021 genetic background could not be restored to nodulation by supplementation with exogenous amino acids even though their Nod factor production appeared to be normal.



Author(s):  
Wanting Jiao

Allostery, in which binding of ligands to remote sites causes a functional change in the active sites, is a fascinating phenomenon observed in enzymes. Allostery can occur either with or without significant conformational changes in the enzymes, and the molecular basis of its mechanism can be difficult to decipher using only experimental techniques. Computational tools for analyzing enzyme sequences, structures, and dynamics can provide insights into the allosteric mechanism at the atomic level. Combining computational and experimental methods offers a powerful strategy for the study of enzyme allostery. The aromatic amino acid biosynthesis pathway is essential in microorganisms and plants. Multiple enzymes involved in this pathway are sensitive to feedback regulation by pathway end products and are known to use allostery to control their activities. To date, four enzymes in the aromatic amino acid biosynthesis pathway have been computationally investigated for their allosteric mechanisms, including 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase, anthranilate synthase, chorismate mutase, and tryptophan synthase. Here we review the computational studies and findings on the allosteric mechanisms of these four enzymes. Results from these studies demonstrate the capability of computational tools and encourage future computational investigations of allostery in other enzymes of this pathway.



1987 ◽  
Vol 208 (1-2) ◽  
pp. 159-167 ◽  
Author(s):  
Kiyoji Nishiwaki ◽  
Naoyuki Hayashi ◽  
Shinji Irie ◽  
Dong-Hyo Chung ◽  
Satoshi Harashima ◽  
...  


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