Biosynthesis aminoacids

Bagge P, Larsson C. 1986 Biosynthesis of aromatic aminoacids by highly purified spinach chloroplasts—compartmentation and regulation of the reactions. Physiol Plantarum 68 641-647. 

Substrate channeling is a process by which two or more sequential enzymes in a pathway interact to transfer a metabolite (or intermediate) from one enzyme to another without allowing free diffusion of the metabolite into bulk solvent. (Ovadi, 1991 Srere, 1987 Anderson, 1999). The substrate tunneling is one of fundamental process of regulating enzymatic processes in cells. Glycolysis, biosynthesis of nucleic acids, aminoacids, and fatty acids are found to be among these processes. 

In another study (Mavrovouniotis et al., 1990), the biosynthesis of the aminoacid lysine was extensively investigated. In that case study, several reactions (shown in gray in Fig. 22) were assumed nonfunctional, and alternatives that avoid these steps were sought. 

To some extent this may be subjective, imposing a human interpretation on the observations, but it also reflects an objective reality some reactions carry a greater flux of metabohtes than others, some are active in a wider range of cell types than others, and so on. To understand the entire chart, therefore, it is useful to collect the reactions into groups of transformation sequences known as metabolic pathways. The number of steps considered to be one pathway can be very small if very few steps are needed to convert one important metabolite into another. For example, serine biosynthesis is a three-step pathway, in which the aminoacid serine is synthesized from 3-phosphoglycerate. At the other extreme, beta-oxidation, the process that converts fatty acids from the form in which they are stored in fat cells into the form in which they are metabolically active, involves seven repetitions of the same four types of step, making an unbranched pathway of nearly 30 reactions. 

Sulfonylureas are systemic herbicides absorbed by the foliage and roots. They act by inhibiting acetolactate synthase, a key enzyme in the biosynthesis of branched chain aminoacids." This results in stopping cell division and plant growth. The most important degradation pathways of sulfonylureas are chemical hydrolysis and microbial degradation. 

There is a very large area of enzyme targets as illustrated in Table 4.2. For example, dihydrofolate reductase (DHFR) catalyses the NADPH-linked reduction of dihydrofolate to tetrahydrofolate. The tetrahydrofolate are cofactors for the biosynthesis of nucleic acids and aminoacids. The reduction of their level induces a limitation of cell growth. ... 

The use of two types of liquid membranes is described in [302] liquid emulsion membranes (LEMs), and supported liquid membranes (SLMs), where isoparaffin or kerosene and their mixtures were used as organic phases. A surfactant of the type of Span 80 served as emulsifier. LEMs are used, for example, for selective separation of L-phenylalanine from a racemic mixture of L-leucine biosynthesis as well as conversion of penicillins to 6-APA (6-aminopenicillanic acid). SLMs have a higher stability. A number of their commercial applications have been studied, e.g. in separation of penicillin from fermentation broth, as well as in the recovery of citric acid, lactic acid and some aminoacids. Compared with other separation methods (ultrafiltration, ultracentrifugation and ion exchange), LEMs and SLMs are advantageous in the separation of stereospecific isomers in racemic mixtures. 

Williams, M., Dietary supplements and sports performance Aminoacids, Int, J, Sport Nutr., 2, 63, 2005. Walker, J.B., Creatine Biosynthesis, regulation and function, Adv. Enzymol. Relat. Areas. Mol. Med., 50, 177, 1979. 

One of the more recent applications of carbene insertion into 0-H bond of alcohols includes the synthesis of chorismic (and pseudochoris-mic) acid [81], which occupies in microorganisms and plants, a strategic position in the shikimate pathway [82] as the key branch point intermediate governing the biosynthesis of aromatic aminoacids, isoprenoid qui-nones, bacterial and plant growth regulators, and other vital compounds. 

One of the known mechanisms of biosynthesis is shown in the next scheme. The enzyme aminotransferase transfers the amino group from the precursor amino acid to the a-ketoacid, which is rearranged into the product amino acid. In this process, the precursor amino acid is transformed into the corresponding a-ketoacid. It must be pointed out that besides transferring the amino group, the enzyme aminotransferase also preserves the stereochemistry the L-precursor amino acid leads to the formation of the L-product aminoacid. This mechanism presented below is for the biosynthesis of L-glutamic acid. 

These compounds are synthesized endogenously from three classes of aminoacids, which require three separated metabolic pathways. The biosynthesis pathway can be divided in three independent... 

Malinka, Z., Harazim, P., Bfemek, J. and Valik, J. (1987) Influence of aminoacids in ergot alkaloid biosynthesis. Bulletin Cs. spol. biochem. pfi CSAV, 15, 107 (In Czech). 

We can then conclude that the biosynthesis of wall glycoproteins requires as a primary step protein formation and specifically synthesis of the mannose acceptor proteins. It also requires formation of the enzymic apparatus which catalyzes polymerization of aminoacids and carbohydrates. 

It follows that the biosynthesis of this unusual aminoacid traps an high amount of cysteine. The possibility of the use of cysteine for TAU synthesis in the cat, either through the CSA or the cysteamine pathway, is therefore impaired. 

Quite surprisingly V. aerophoba failed to incorporate radioactivity from [U- " C]-L-tyrosine into aerothionin (7), aeroplysinin-1 (4) and the dienone (1) inactive aerothionin was also isolated when the animals were fed with [U- " C]-L-ornithine (71). However the sponges utilized these aminoacids for the synthesis of fatty acids. A very slow rate of biosynthesis might account for these results. A dietary origin for these compounds can be also suspected in this connection the recent report of the isolation of the brominated esters (19) and (20) (after methylation) from hydrolyzed extracts of the red alga Halopytis incurvus (41) seems relevant. 

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