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Greener Synthesis of Natural Products
Published in Ahindra Nag, Greener Synthesis of Organic Compounds, Drugs and Natural Products, 2022
Renata Kołodziejska, Renata Studzińska, Hanna Pawluk, Alina Woźniak
ω-Transaminases (ω-TA) which generate C-N bond formation, are also increasingly used in asymmetric synthesis. The natural function of these enzymes is to catalyze the transamination reaction between amino acids and α-keto acids. The use of ω-transaminases in the synthesis of piperidine alkaloids has been reported (Figure 14.35). Reductive amination of δ-diketones catalyzed by various ω-transaminases (Chromobacterium violaceum, Bacillus megaterium, (R)-Arthrobacter, Aspergillus terreus, and Hyphomonas neptuniuoccurs) only at the sterically less demanding ω-1 ketone moiety giving optically pure amino ketones. Cis-2,6-disubstituted piperidines as single stereoisomers are formed as a result of spontaneous cyclization of amino ketones to imines, which are catalytically hydrogenated in the next step.127 Regioselective asymmetric mono-amination of 1,5-diketones catalyzed by ω-transaminase was used to the chemo-enzymatic synthesis of dihydropinidine and epi-dihydropinidine, by using (R)- and (S)-selective ω-transaminases.128
Introduction
Published in Debabrata Das, Debayan Das, Biochemical Engineering, 2019
Nitrogen metabolism in the cell usually occurs by the hydrolysis of proteins to peptides and amino acids by the action of proteases. The amino acids are further converted to organic acids by the deamination process. Depending on the enzyme systems involved, deamination can be oxidative, reductive, or dehydrative. Apart from deamination, transamination is another mechanism for the conversion of amino acids to organic acids. In this process, the amino group is exchanged for the keto group of α-keto acid. Like carbohydrates and proteins, nucleic acids can also be used for the carbon, nitrogen, and energy sources. Nucleic acids can be hydrolyzed by nucleases into its precursor molecules, i.e., sugar, nitrogenous base, and phosphorus. Sugar can be used by glycolysis and TCA cycle under aerobic conditions, and phosphorus can be used for the synthesis of ATP, phospholipid, and nucleic acid synthesis. The nitrogenous bases are further degraded into urea and acetic acid, ultimately forming ammonia and CO2.
Biological Responses in Context
Published in Arthur T. Johnson, Biology for Engineers, 2019
Amino acids are used by the body to form proteins, hormones, and enzymes. Transamination reactions can convert one amino acid into another to meet immediate needs. However, just as there are essential fatty acids, there are also essential amino acids. These amino acids cannot be synthesized in the body and must come from external sources. Humans require phenylalanine, valine, tryptophan, threonine, lysine, leucine, isoleucine, and methionine as essential amino acids. All other amino acids in the body can be synthesized at rates sufficient to meet body needs. If any one of the amino acids necessary to synthesize a particular protein is not available, then the other amino acids that would have gone into the protein are deaminated, and their excess nitrogen is excreted as urea (Ganong, 1963).
Energy budget in Alona guttata (Chydoridae: Aloninae) and toxicant-induced alterations
Published in Journal of Environmental Science and Health, Part A, 2019
Olga C. Osorio-Treviño, Mario A. Arzate-Cárdenas, Roberto Rico-Martínez
Alona guttata exhibited a higher sensitivity for protein depletion in proportions of 0.05 LC50 to 0.20 LC50 for DM, and 0.1 to 0.2 LC50 for Pb2+, although at the highest concentrations tested, the energy budget was affected in all its components at similar depletion rates, which denotes a high demand for energy to deal with the effect of toxic exposure. High protein consumption has been related to proteolysis and the release of free amino acids that, after the transamination, could be incorporated into the tricarboxylic acid cycle (anaplerotic metabolic pathway) to acquire reducing power and finally the energy required for maintenance and detoxification.[30] This effect is commonly observed in daphnids[31,32] but it seems that the damage produced in Alona's tissues was extensive, and it compromised fertility and survival.
Potential of amyl alcohol mixtures derived from Scenedesmus quadricauda microalgae biomass as third generation bioenergy for compression ignition engine applications using multivariate-desirability analysis
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
The hydrolyzate from the enzymatic hydrolysis is fermented by introducing S. cerevisiae grown in an agar inoculum with 5 g/L of peptone, 2.5 g/L of malt, 8 g/L of glucose, 12 g/L of agar, and yeast extract, maintained at 4°C (Phwan et al. 2019). A 4% (v/v) yeast culture and an E.coli strain were acquired from Sigma–Aldrich for the biosynthesis of essential amino acids like threonine and isoleucine. Ehrlich biosynthetic pathway was followed for the synthesis of amyl alcohol. The first step of this pathway is the degradation of amino acid by transamination using aminotransferase (AAT) to give 2-ketoacids. The second step is the decarboxylation of 2-ketoacid using 2-ketoacid decarboxylase (KDC) which then yields an aldehyde and CO2. Finally, alcohol dehydrogenase (ADH) is used in the reduction stage to convert aldehyde to higher alcohol. These reaction phases in the Ehrlich pathway are shown in Figure 1. In this context, the glucose composition from the biomass hydrolyzate is processed into phosphoenolpyruvate (PEP). The first committed reaction for this methodology is initiated by the condensation of pyruvate and 2-ketobutyrate which are produced by isoleucine and threonine. These amines are synthesized by an E.coli strain which is overexpressed with a suppressed feedback inhibition catalyzed by acetohydroxyacid synthase enzyme (AHAS). The deamination was initiated by threonine deaminase for converting 2-ketobutyrate/ pyruvate to 2-keto-3-methyl-valerate. Subsequently, in the decarboxylation process, yeast catalyzes KDC encoded pyruvate decarboxylase isozyme – 1 for initiating the production of 2-methyl-1-butyraldehyde and CO2 (Shanmugam et al. 2021). Finally, the redox reaction is initiated by nicotinamide adenine dinucleotide (NADH) to reduce the aldehyde into amyl alcohol. The whole fermentation process was carried out in a controlled environment within a shaking incubator at 160 rpm for 48 hours at 30°C, anaerobically. The final solution of the alcoholic mixture is collected and a sample of it is subjected to a gas chromatograph test to analyze its constituents. Primarily, the mixture comprised ethanol, water, and fusel oil in different percentages. The generated chromatograph as shown in Figure 2 depicts a reasonable trace of active amyl alcohol and other higher carbon-chained alcohol such as isobutanol, pentanol, and hexanol. This further proves that the effectivity of the isoleucine produced through this biosynthetic process. The mixtures were separated by distillation and the majority of the primary alcohols like methanol, ethanol, and propanol were stored separately for another research work and the secondary higher alcohols like butanol and pentanol were separated and collected. Out of this the active amyl alcohol was distilled and stored to assess its physicochemical properties. The physicochemical properties shown in Table 1 for AA100 projects a similar trend as other five-carbon chained alcohol like pentanol done in multiple studies for fuel application (Yesilyurt, Eryilmaz, and Arslan 2018). This further substantiates the nature of the extracted alcohol and it can be analyzed to be utilized as diesel fuel surrogates at various compositions.