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BCAT1, a cytosolic aminotransferase for branched-chain amino acids (BCAAs), is aberrantly activated and functionally required for disease progression in chronic myeloid leukaemia. Role of metabolic changes in cancer progression Cellular metabolic changes are commonly observed in various cancers. How they directly influence cancer development is under investigation. Ayuna Hattori et al . show that the metabolic enzyme BCAT1 is upregulated in chronic myeloid leukemia, mediated by Musashi2. BCAT1 is shown to function by aminating branch-chain keto acids to BCAAs. Inhibition of BCAT1 leads to differentiation and impaired propagation of chronic myeloid leukaemia in mice. In humans, elevated BCAT1 expression is also associated with poorer outcome of the illness and therefore might be used alongside other biomarkers to help predict disease outcome in patients. Reprogrammed cellular metabolism is a common characteristic observed in various cancers 1 , 2 . However, whether metabolic changes directly regulate cancer development and progression remains poorly understood. Here we show that BCAT1, a cytosolic aminotransferase for branched-chain amino acids (BCAAs), is aberrantly activated and functionally required for chronic myeloid leukaemia (CML) in humans and in mouse models of CML. BCAT1 is upregulated during progression of CML and promotes BCAA production in leukaemia cells by aminating the branched-chain keto acids. Blocking BCAT1 gene expression or enzymatic activity induces cellular differentiation and impairs the propagation of blast crisis CML both in vitro and in vivo . Stable-isotope tracer experiments combined with nuclear magnetic resonance-based metabolic analysis demonstrate the intracellular production of BCAAs by BCAT1. Direct supplementation with BCAAs ameliorates the defects caused by BCAT1 knockdown, indicating that BCAT1 exerts its oncogenic function through BCAA production in blast crisis CML cells. Importantly, BCAT1 expression not only is activated in human blast crisis CML and de novo acute myeloid leukaemia, but also predicts disease outcome in patients. As an upstream regulator of BCAT1 expression, we identified Musashi2 (MSI2), an oncogenic RNA binding protein that is required for blast crisis CML. MSI2 is physically associated with the BCAT1 transcript and positively regulates its protein expression in leukaemia. Taken together, this work reveals that altered BCAA metabolism activated through the MSI2–BCAT1 axis drives cancer progression in myeloid leukaemia.

A ( S )-selective amine transaminase from a Streptomyces strain, Sbv333-ATA, is a biocatalyst showing both high thermostability with a melting temperature of 85 °C and broad substrate specificity for the amino acceptor. This enzyme was further characterized both biochemically and structurally. The Sbv333-ATA is stable in the presence of up to 20% ( v / v ) of the water-miscible cosolvents methanol, ethanol, acetonitrile, and dimethyl sulfoxide, and in biphasic systems with petroleum ether, toluene, and ethyl acetate as an organic phase. The enzyme showed also a good activity toward different amino donors, such as ( S )-methylbenzylamine and 2-phenylethylamine, aliphatic mono- and di-amines, like propylamine and cadaverine, and selected amino acids. However, more sterically hindered aromatic amines were not accepted. Based on the knowledge of the three-dimensional structures obtained, a rational approach to site specific mutagenesis was carried out to broaden the substrate specificity of Sbv333-ATA. The mutant W89A showed the highest activity toward bulky amines as substrates, such as the diaromatic compound 1,2-diphenylethylamine. The 3D structures of the holo and inhibitor gabaculine bound forms of native Sbv333-ATA, and holo W89A and F61C mutants were determined at high resolutions of 1.49, 1.24, and 1.31 (both mutants) Å, respectively. These structures were important for revealing further details of the active site binding pockets of the Sbv333-ATA and its mechanism. Key points • Sbv333-ATA is a highly thermostable transaminase with a broad substrate scope. • Sbv333-ATA remains active in various organic cosolvents and biphasic systems. • Mutant W89A expands substrate range to accept bulky diaromatic amines. Graphical abstract

Biobased furans have emerged as chemical building blocks for the development of materials because of their diverse scaffolds and as they can be directly prepared from sugars. However, selective, efficient, and cost-effective scalable conversion of biobased furans remains elusive. Here, we report a robust transaminase (TA) from Shimia marina (SMTA) that enables the scalable amination of biobased furanaldehydes with high activity and broad substrate specificity. Crystallographic and mutagenesis analyses provide mechanistic insights and a structural basis for understanding SMTA, which enables a higher substrate conversion. The enzymatic cascade process established in this study allows one-pot synthesis of 2 ,5 - bis (aminomethyl)furan (BAMF) and 5 -(aminomethyl)furan- 2 -carboxylic acid from 5 -hydroxymethylfurfural. The biosynthesis of various furfurylamines, including a one-pot cascade reaction for BAMF generation using whole cells, demonstrates their practical application in the pharmaceutical and polymer industries. Biobased furans are important chemical building blocks for the development of materials, but selective, efficient, and cost-effective scalable conversion of biobased furans remains elusive. Here, the authors report a transaminase from Shimia marina (SMTA) that enables the scalable amination of biobased furanaldehydes with high activity and broad substrate specificity and provide structural and mechanistic insights into SMTA activity.

Chiral amines are essential precursors in the production of biologically active compounds, including several important drugs. Among the biocatalytic strategies that have been developed for their synthesis, the use of ω-transaminases (ω-TA) appears as an attractive alternative allowing the stereoselective amination of prochiral ketones. However, the problems associated with narrow substrate specificity, unfavourable reaction equilibrium and expensive amine donors still hamper its industrial application. The search for novel enzymes from nature can contribute to expand the catalytic repertoire of ω-TA and help to circumvent some of these problems. A genome mining approach, based on the work described by Höhne et al., was applied for selection of potential R -ω-TA. Additional criteria were used to select an enzyme that differs from previously described ones. A candidate R -ω-TA from Capronia semiimmersa was selected, cloned and expressed in Escherichia coli . Interestingly, alignment of this enzyme with previously reported TA sequences revealed the presence of two additional amino acid residues in a loop close to the active site. The impact of this change was analysed with a structural model based on crystallized R -ω-TAs. Analysis of the substrate specificity of R -ω-TA from C . semiimmersa indicates that it accepts a diversity of ketones as substrates yielding the corresponding amine with good yields and excellent enantioselectivity. The expressed enzyme accepts isopropylamine as amine donor what makes it suitable for industrial processes.

Background: GABA (γ-aminobutyric acid) is a non protein amino acid that has been reported to accumulate in a number of plant species when subjected to high salinity and many other environmental constraints. However, no experimental data are to date available on the molecular function of GABA and the involvement of its metabolism in salt stress tolerance in higher plants. Here, we investigated the regulation of GABA metabolism in Arabidopsis thaliana at the metabolite, enzymatic activity and gene transcription levels upon NaCl stress. Results: We identified the GABA transaminase (GABA-T), the first step of GABA catabolism, as the most responsive to NaCl. We further performed a functional analysis of the corresponding gene POP2 and demonstrated that the previously isolated loss-of-function pop2-1 mutant was oversensitive to ionic stress but not to osmotic stress suggesting a specific role in salt tolerance. NaCl oversensitivity was not associated with overaccumulation of Na+ and Cl- but mutant showed a slight decrease in K+. To bring insights into POP2 function, a promoter-reporter gene strategy was used and showed that POP2 was mainly expressed in roots under control conditions and was induced in primary root apex and aerial parts of plants in response to NaCl. Additionally, GC-MS- and UPLC-based metabolite profiling revealed major changes in roots of pop2-1 mutant upon NaCl stress including accumulation of amino acids and decrease in carbohydrates content. Conclusions: GABA metabolism was overall up-regulated in response to NaCl in Arabidopsis. Particularly, GABA-T was found to play a pivotal function and impairment of this step was responsible for a decrease in salt tolerance indicating that GABA catabolism was a determinant of Arabidopsis salt tolerance. GABA-T would act in salt responses in linking N and C metabolisms in roots.

This randomized trial showed that two different doses of oral cannabidiol resulted in greater reductions in drop-seizure and total-seizure frequencies than placebo among patients with the Lennox–Gastaut syndrome, a severe developmental epileptic encephalopathy.

ω-Transaminase (ω-TA) is a promising biocatalyst for the synthesis of chiral amines. In this study, a ω-TA derived from Vitreoscilla stercoraria DSM 513 ( Vs TA) was heterologous expressed in recombinant E. coli cells and applied to reduce 4′-(trifluoromethyl)acetophenone (TAP) to ( S )-1-[4-(trifluoromethyl)phenyl]ethylamine (( S )-TPE), a pharmaceutical intermediate of chiral amine. Aimed to a more efficient synthesis of ( S )-TPE, Vs TA was further engineered via a semi-rational strategy. Compared to wild-type Vs TA, the obtained R411A variant exhibited 2.39 times higher activity towards TAP and enhanced catalytic activities towards other prochiral aromatic ketones. Additionally, better thermal stability for R411A variant was observed with 25.4% and 16.3% increase in half-life at 30 °C and 40 °C, respectively. Structure-guided analysis revealed that the activity improvement of R411A variant was attributed to the introduction of residue A411, which is responsible for the increase in the hydrophobicity of substrate tunnel and the alleviation of steric hindrance, thereby facilitating the accessibility of hydrophobic substrate TAP to the active center of Vs TA. This study provides an efficient strategy for the engineering of ω-TA based on semi-rational approach and has the potential for the molecular modification of other biocatalysts. Graphical Abstract

Transaminases (TAms) are important enzymes for the production of chiral amines for the pharmaceutical and fine chemical industries. Novel TAms for use in these industries have been discovered using a range of approaches, including activity-guided methods and homologous sequence searches from cultured microorganisms to searches using key motifs and metagenomic mining of environmental DNA libraries. This mini-review focuses on the methods used for TAm discovery over the past two decades, analyzing the changing trends in the field and highlighting the advantages and drawbacks of the respective approaches used. This review will also discuss the role of protein engineering in the development of novel TAms and explore possible directions for future TAm discovery for application in industrial biocatalysis.Key Points• The past two decades of TAm enzyme discovery approaches are explored.• TAm sequences are phylogenetically analyzed and compared to other discovery methods.• Benefits and drawbacks of discovery approaches for novel biocatalysts are discussed.• The role of protein engineering and future discovery directions is highlighted.

Inclisiran, a small interfering RNA that targets PCSK9 mRNA, was given as a single injection at baseline or in two doses at baseline and 90 days. At 180 days, LDL cholesterol was significantly lowered among persons at high cardiovascular risk who had elevated levels at baseline. Low-density lipoprotein (LDL) cholesterol is a causal factor in atherosclerotic cardiovascular disease. Statins have been shown to reduce LDL cholesterol levels and cardiovascular events in large outcome trials, findings that have made them the therapeutic cornerstone of clinical practice. 1 Despite the proven efficacy of statins, there is considerable variability in individual responses to these drugs. 2 Furthermore, some observational data suggest that as many as half of persons who begin statin therapy discontinue it within a year. 3 Moreover, among patients receiving statin therapy who are at high risk for cardiovascular disease and who have persistent elevation of LDL cholesterol levels, the . . .

Antiestrogen-resistant and triple-negative breast tumors pose a serious clinical challenge because of limited treatment options. We assessed global gene expression changes in antiestrogen-sensitive compared with antiestrogen-resistant (two tamoxifen resistant and two fulvestrant resistant) MCF-7 breast cancer cell lines. The branched-chain amino acid transaminase 1 ( BCAT1 ), which catalyzes the first step in the breakdown of branched-chain amino acids, was among the most upregulated transcripts in antiestrogen-resistant cells. Elevated BCAT1 expression was confirmed in relapsed tamoxifen-resistant breast tumor specimens. High intratumoral BCAT1 levels were associated with a reduced relapse-free survival in adjuvant tamoxifen-treated patients and overall survival in unselected patients. On a tissue microarray ( n =1421), BCAT1 expression was detectable in 58% of unselected primary breast carcinomas and linked to a higher Ki-67 proliferation index, as well as histological grade. Interestingly, BCAT1 was predominantly expressed in estrogen receptor-α-negative/human epidermal growth factor receptor-2-positive (ERα-negative/HER-2-positive) and triple-negative breast cancers in independent patient cohorts. The inverse relationship between BCAT1 and ERα was corroborated in various breast cancer cell lines and pharmacological long-term depletion of ERα induced BCAT1 expression in vitro. Mechanistically, BCAT1 indirectly controlled expression of the cell cycle inhibitor p27 Kip1 thereby affecting pRB. Correspondingly, phenotypic analyses using a lentiviral-mediated BCAT1 short hairpin RNA knockdown revealed that BCAT1 sustains proliferation in addition to migration and invasion and that its overexpression enhanced the capacity of antiestrogen-sensitive cells to grow in the presence of antiestrogens. Importantly, silencing of BCAT1 in an orthotopic triple-negative xenograft model resulted in a massive reduction of tumor volume in vivo , supporting our findings that BCAT1 is necessary for the growth of hormone-independent breast tumors.