Redesign of a short-chain dehydrogenase/reductase for asymmetric synthesis of ethyl (R)-2-hydroxy-4-phenylbutanoate based on per-residue free energy decomposition and sequence conservatism analysis

As an important building block for the synthesis of angiotensin-converting enzyme inhibitors,ethyl(R)-2-hy-droxyl-4-phenylbutanoate[(R)-HPBE]has attracted increasing attention.The key to industrial biosynthesis of(R)-HPBE is a biocatalyst that efficiently reduces ethyl 2-oxo-4-phenylbutanoate(OPBE)with high R-enantiose-lectivity.This paper proposed a strategy for identifying key residues involved in enantioselectivity control based on per-residue free energy decomposition and sequence conservatism analysis.Using this strategy,4 noncon-servative sites with high energy contribution to binding of OPBE were chosen as engineering targets,generating variant Mu27 with 99%conversion and 98%(R)ee value at substrate loading of up to 500 mmol/L.MD simu-lations suggested the higher stability and formation probability of Mu27-OPBEproR prereaction state as key rea-sons for the excellent R-enantioselectivity of Mu27 towards OPBE.The success in this study provides a viable approach for rational design of alcohol dehydrogenases with high enantioselectivity towards unnatural substrates.

Skeletal Muscle Magnetic Resonance Imaging of the Lower Limbs in Late-onset Lipid Storage Myopathy with Electron Transfer Flavoprotein Dehydrogenase Gene Mutations

Background： Lipid storage myopathy （LSM） is a genetically heterogeneous group with variable clinical phenotypes. Late-onset multiple acyl-coenzyme A dehydrogenation deficiency （MADD） is a rather common form of LSM in China. Diagnosis and clinical management of it remain challenging, especially without robust muscle biopsy result and genetic detection. As the noninvasion and convenience, muscle magnetic resonance imaging （MRI） is a helpful assistant, diagnostic tool for neuromuscular disorders. However, the disease-specific MRI patterns of muscle involved and its diagnostic value in late-onset MADD have not been systematic analyzed. Methods： We assessed the MRI pattern and fat infiltration degree of the lower limb muscles in 28 late-onset MADD patients, combined with detailed clinical features and gene spectrum. Fat infiltration degree of the thigh muscle was scored while that ofgluteus was described as obvious or not. Associated muscular atrophy was defined as obvious muscle bulk reduction. Results： The mean scores were significantly different among the anterior, medial, and posterior thigh muscle groups. The mean of fat infiltration scores on posterior thigh muscle group was significantly higher than either anterior or medial thigh muscle group （P 〈 0.00 l）. Moreover, the mean score on medial thigh muscle group was significantly higher than that of anterior thigh muscle group （P 〈 0.01）. About half of the patients displayed fat infiltration and atrophy in gluteus muscles. Of 28 patients, 12 exhibited atrophy in medial and/ or posterior thigh muscle groups, especially in posterior thigh muscle group. Muscle edema pattern was not found in all the patients. Conclusions： Late-onset MADD patients show a typical muscular imaging pattern of fat infiltration and atrophy on anterior, posterior, and medial thigh muscle groups, with major involvement of posterior thigh muscle group and gluteus muscles and a sparing involvement of anterior thigh compartment. Our findings also suggest that muscle MRI of lower limbs is a helpful tool in guiding clinical evaluation on late-onset MADD.

Cloning and functional characterization of two cDNAs encoding NADPH-dependent 3-ketoacyl-CoA reductased from developing cotton fibers

Genes encoding enzymes involved in biosynthesis of very long chain fatty acids were significantly up-regulatedduring early cotton fiber development. Two cDNAs, GhKCR1 and GhKCR2 encoding putative cotton 3-ketoacyl-CoAreductases that catalyze the second step in fatty acid elongation, were isolated from developing cotton fibers. GhKCR1and 2 contain open reading frames of 963 bp and 924 bp encoding proteins of 320 and 307 amino acid residues,respectively. Quantatitive RT-PCR analysis showed that both these genes were highly preferentially expressed duringthe cotton fiber elongation period with much lower levels recovered from roots, stems and leaves. GhKCR1 and 2showed 30%-32% identity to Saccharomyces cerevisiae Ybr159p at the deduced amino acid level. These cotton cDNAswere cloned and expressed in yeast haploid ybr159w? mutant that was deficient in 3-ketoacyl-CoA reductase activity.Wild-type growth rate was restored in ybr159w? cells that expressed either GhKCR1 or 2. Further analysis showed thatGhKCR1 and 2 were co-sedimented within the membranous pellet fraction after high-speed centrifugation, similar to theyeast endoplasmic reticulum marker ScKar2p. Both GhKCR(s) showed NADPH-dependent 3-ketoacyl-CoA reductaseactivity in an in vitro assay system using palmitoyl-CoA and malonyl-CoA as substrates. Our results suggest thatGhKCR1 and 2 are functional orthologues of ScYbr159p.

Transfer RNA-derived fragment tRF-23-Q99P9P9NDD promotes progression of gastric cancer by targeting ACADSB

Gastric cancer(GC)is one of the most common gastrointestinal tumors.As a newly discovered type of non-coding RNAs,transfer RNA(tRNA)-derived small RNAs(tsRNAs)play a dual biological role in cancer.Our previous studies have demonstrated the potential of tRF-23-Q99P9P9NDD as a diagnostic and prognostic biomarker for GC.In this work,we confirmed for the first time that tRF-23-Q99P9P9NDD can promote the proliferation,migration,and invasion of GC cells in vitro.The dual luciferase reporter gene assay confirmed that tRF-23-Q99P9P9NDD could bind to the 3'untranslated region(UTR)site of acyl-coenzyme A dehydrogenase short/branched chain(ACADSB).In addition,ACADSB could rescue the effect of tRF-23-Q99P9P9NDD on GC cells.Next,we used Gene Ontology(GO),the Kyoto Encyclopedia of Genes and Genomes(KEGG),and Gene Set Enrichment Analysis(GSEA)to find that downregulated ACADSB in GC may promote lipid accumulation by inhibiting fatty acid catabolism and ferroptosis.Finally,we verified the correlation between ACADSB and 12 ferroptosis genes at the transcriptional level,as well as the changes in reactive oxygen species(ROS)levels by flow cytometry.In summary,this study proposes that tRF-23-Q99P9P9NDD may affect GC lipid metabolism and ferroptosis by targeting ACADSB,thereby promoting GC progression.It provides a theoretical basis for the diagnostic and prognostic monitoring value of GC and opens upnew possibilities for treatment.