Living cell synthesis

The synthesis of enzymes is a continuous process in every living celL Synthesis of acid hydrolases in mammalian cells requires not only the possession of the appropriate gene but also the presence of a specific substrate or a substance closely related to it to act as specific enzyme inducer. The phenomenon is termed enzyme induction. The opposite phenomenon exists and is referred to as enzyme repression. Acid hydrolases in a cell will depend, therefore, upon the presence of the particular gene... 

In many cases only the racemic mixtures of a-amino acids can be obtained through chemical synthesis. Therefore, optical resolution (42) is indispensable to get the optically active L- or D-forms in the production of expensive or uncommon amino acids. The optical resolution of amino acids can be done in two general ways physical or chemical methods which apply the stereospecific properties of amino acids, and biological or enzymatic methods which are based on the characteristic behavior of amino acids in living cells in the presence of enzymes. 

Synthesis of industrial chemicals by microbial cells may be by fermentation (free, living cells), immobilised growing cells, immobilised resting cells or immobilised dead cells. 

Ribosomes are ancient ribonucleoprotein complexes that are the sites of protein synthesis in living cells. Their core structures and fundamental functional mechanisms have been conserved throughout the three domains of life bacteria, archaea and eukaryotes. All ribosomes are organized into two subunits that are defined by their apparent sedimentation coefficient, measured in Svedberg units (S). There is a general... 

Wang M, Gao M, Miller KD et al (2009) Simple synthesis of carbon-11 labeled styryl dyes as new potential PET RNA-specific, living cell imaging probes. Eur J Med Chem 44 2300-2306... 

Lee JS, Kang NY, Kim YK, Samanta A, Feng S, Kim HK, Vendrell M, Park JH, Chang YT (2009) Synthesis of a BODIPY library and its application to the development of live cell glucagon imaging probe. J Am Chem Soc 131 10077-10082... 

The ribosome is a ribozyme this is how Cech (2000) commented on the report by Nissen et al. (2000) in Science on the successful proof of ribozyme action in the formation of the peptide bond at the ribosome. It has been known for more than 30 years that in the living cell, the peptidyl transferase activity of the ribosome is responsible for the formation of the peptide bond. This process, which takes place at the large ribosome subunit, is the most important reaction of protein biosynthesis. The determination of the molecular mechanism required more than 20 years of intensive work in several research laboratories. The key components in the ribosomes of all life forms on Earth are almost the same. It thus seems justified to assume that protein synthesis in a (still unknown) common ancestor of all living systems was catalysed by a similarly structured unit. For example, in the case of the bacterium E. coli, the two subunits which form the ribosome consist of 3 rRNA strands and 57 polypeptides. Until the beginning of the 1980s it was considered certain that the formation of the peptide bond at the ribozyme could only be carried out by ri-bosomal proteins. However, doubts were expressed soon after the discovery of the ribozymes, and the possibility of the participation of ribozymes in peptide formation was discussed. 

Enzymatic synthesis in vivo (in living cells) via biosynthetic pathways... 

The remarkable processes of life and decay are based on the ability of enzyme systems to function in a dual role in the dynamic metabolism associated with living systems. On the one hand, the enzymes present in organisms promote the synthesis of complex organic compounds from low molecular weight intermediates, and, on the other hand and simultaneously, other enzymes present therein facilitate the degradation of such compounds. Thus, in the study of the source and ultimate fate of a natural substance in living cells, the investigation of both the pathway of its synthesis and its breakdown are of equal importance. 

Oligosaccharides and glycoconjugates in living cells often exist as closely related mixtures. Their isolation from natural sources in homogeneous form is therefore very difficult, involving tedious purification and difficult characterization. This sequence of steps tends to result in low yields. This difficult situation presents chemical synthesis with a major opportunity to positively affect progress in the biochemical understanding of the processes described above.4... 

Wohler s synthesis of urea by which a product of the living cell was first prepared artificially more than a century ago is the prototype of many addition reactions which take place with the reactive molecules of cyanic acid and its esters, as well as with the series of analogous thio-compounds. In these reactions NH3 is added to the C = N double bond ... 

Wohler s preparation of urea from ammonium cyanate, which could in principle be derived totally from inorganic constituents, is cited as an early demonstration (1828) that living cells were not obligatorily required for the synthesis of natural products. I can prepare urea without requiring a kidney or an animal—either man or dog. Three years after the death of Pasteur the finding by Hans and Edouard Buchner (1897) that fermentation still occured in a cell-free extract from yeast and so did not require the presence of organized cells, was virtually the final nail in the coffin for vitalism and an essential preliminary to the study of intermediary metabolism (Chapter 4). 

The paper by Krebs and Henseleit (1932), Experiments on the Formation of Urea in Animal Bodies (Klinische Wochenschrift 11,759), contained the phrases... in the synthesis of urea in the living cell, ornithine acts like a catalyst. We therefore draw the conclusion. .. that the primary reaction for the synthesis of urea from ammonia is... 

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