The 138th residue of acetohydroxyacid synthase in Corynebacterium glutamicum is important for the substrate binding specificity

Qian

et al. 2022

npj Parkinsons Dis.

Disturbances of circulating amino acids have been demonstrated in patients with Parkinson’s disease (PD). However, there have been no consistent results for branched-chain amino acids (BCAAs) and aromatic amino acids (AAAs), and related factors have not been explored. We aimed to explore plasma BCAA and AAA profiles in PD patients, and identify their correlations with clinical characteristics and the gut microbiota. Plasma BCAA (leucine, isoleucine, and valine) and AAA (tyrosine and phenylalanine) levels were measured in 106 PD patients and 114 controls. Fecal samples were collected from PD patients for microbiota sequencing and functional analysis. We found that plasma BCAAs and tyrosine were decreased in PD patients. BCAAs and AAAs were correlated with clinical characteristics and microbial taxa, and, in particular, they were negatively correlated with the Hoehn and Yahr stage. Compared with early PD patients, BCAA and AAA levels were even lower, and microbial composition was altered in advanced PD patients. Predictive functional analysis indicated that predicted genes numbers involved in BCAA biosynthesis were lower in advanced PD patients. What’s more, the fecal abundances of critical genes (ilvB, ilvC, ilvD, and ilvN) involved in BCAA biosynthesis were reduced and fecal BCAA concentrations were lower in advanced PD patients. In conclusion, the disturbances of plasma BCAAs and AAAs in PD patients may be related to the gut microbiota and exacerbated with PD severity. The microbial amino acid metabolism may serve as a potential mechanistic link.

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Plasma branched-chain and aromatic amino acids correlate with the gut microbiota and severity of Parkinson’s disease

Qian

et al. 2022

npj Parkinsons Dis.

“…In this study, compare with WM003, WM004 (the brnQ deletion mutant of encoded by the gene ilvGM reported has the highest specificity for 2-ketobutyric acid [50][51][52], which might determine the amount of l-isoleucine in cells. After analyzing the alignment of partial protein sequences of 100 AHAS and AHAS II paralogs, we found that the 47th residue in AHAS is partially conserved (I or L) but in AHAS II is highly conserved (Y) and the 47th amino acid of AHAS in C. glutamicum corresponds to the 113th amino acid of AHAS in Saccharomyces cerevisiae and participates in the binding of cofactor ThDP and substrate binding [53,54]. Thus, we change the 47th isoleucine of AHAS to tyrosine.…”

Section: Discussionmentioning

confidence: 99%

Metabolic engineering of Corynebacterium glutamicum WM001 to improve l‐isoleucine production

Liu

Biotech and App Biochem

et al. 2020

Self Cite

In this study, L-isoleucine production in Corynebacterium glutamicum WM001 was improved by deleting three genes in the genome, replacing the native promoter of ilvA in the genome, and overexpression of five genes in an alr-based auxotrophic complementation expression system. The three genes deleted in the genome are alaT, brnQ, and alr. Deletion of alaT improved L-isoleucine production by increasing the supply of pyruvate, whereas deletion of brnQ improved L-isoleucine production by blocking the uptake of extracellular L-isoleucine. Exchange of the native promoter of ilvA with promoter tac or tacM could contribute to L-isoleucine production by increasing 2-ketobutyric acid; tac is better than tacM for improving L-isoleucine yield. Different combinations of the genes ilvBN, ppnK, lrp, and brnFE were overexpressed in an alr-based auxotrophic complementation expression system to further improve L-isoleucine production, and the best yield after 72-H flask fermentation was obtained from the strain WM005/pYCW-1-ilvBN2-ppnK1. Without addition of any antibiotics, WM005/pYCW-1-ilvBN2-ppnK1 could produce 32.1 g/L L-isoleucine after 72-H fed-batch fermentation, which is 34.3% increase compared with the original strain WM001.

“…Considering the enzyme’s function analogies during L-valine and L-isoleucine biosynthesis, balancing the expression of the genes and understanding the ability of the key enzyme to bind to specific intermediates may be the major motivator to maximize the production and maintain the optimal cell growth [ 32 , 62 ]. Recently, Liu and colleague demonstrated that the 138th residue of IlvB in AHAS played an important role for binding the main intermediate pyruvate, thereby overexpression of AHAS variant (V404A, IlvB ) in YTW-104 mutant increased L-valine production at 25.93 g L −1 [ 63 ]. In addition, employing the best RBS combinations and promoter engineering are suggested to fine-tune the expression of key biosynthesis genes for L-valine production.…”

Section: Balancing Gene Expression Levelsmentioning

confidence: 99%

Engineering of microbial cells for L-valine production: challenges and opportunities

et al. 2021

L-valine is an essential amino acid that has wide and expanding applications with a suspected growing market demand. Its applicability ranges from animal feed additive, ingredient in cosmetic and special nutrients in pharmaceutical and agriculture fields. Currently, fermentation with the aid of model organisms, is a major method for the production of L-valine. However, achieving the optimal production has often been limited because of the metabolic imbalance in recombinant strains. In this review, the constrains in L-valine biosynthesis are discussed first. Then, we summarize the current advances in engineering of microbial cell factories that have been developed to address and overcome major challenges in the L-valine production process. Future prospects for enhancing the current L-valine production strategies are also discussed.