Biosynthesis amino acid

The metabolism of the carbon chains of amino acids is varied. In humans and laboratory rats, half of the twenty amino acids found in proteins are essential and must be supplied in the diet, either from plant, animal, or microbial sources. The other half can be made from other compounds, especially from the products of carbohydrate metabolism. You can remember the essential amino acids by using a mnemonic  

Very Many Hairy Little Pigs Live In The Torrid Argentine which translates to  

Valine Methionine Histidine Leucine Phenylalanine Lysine Isoleucine Threonine Tryptophan Arginine 

Only human babies require Arginine (which is made in the urea cycle) and histidine. 

What are some common features in amino acid biosynthesis  

Glutamate is formed from NH4+ and a-ketoglutarate in a reductive amination that requires NADPH. This reaction is reversible and is catalyzed by glutamate dehydrogenase (GDH). 

These reactions fix inorganic nitrogen (NH3), forming organic (carhon-containing) nitrogen compounds, such as amino acids, hut they frequently do not operate in this sequential fashion. In fact, the combination of GDH 

Catabolic breakdown of amino acids produces citric acid cycle intermediates 

Animals acquire many of their nutrients in a ready made form from the food that they eat. Plants, however, have to biosynthesise everything that they need for efficient growth. The first section of this chapter discussed photosynthesis, a fundamental biosynthetic process, but plants also synthesise other components that animals do not. These biosynthetic processes are good examples of potentially plant selective herbicidal targets. Amino acids are the building blocks of proteins and as such their biosynthesis is one such process. 

In symbiosis with Fabales, bacteria live as bacteroids in root nodules inside the plant cells. The plant supplies the bacteroids with nutrients, but it also benefits from the fixed nitrogen that the symbionts make available. 

The N2-fixing enzyme used by the bacteria is nitrogenase. It consists of two components an Fe protein that contains an [Fe4S4] cluster as a redox system (see p. 106), accepts electrons from ferredoxin, and donates them to the second component, the Fe-Mo protein. This molybdenum-containing protein transfers the electrons to N2 and thus, via various intermediate steps, produces ammonia (NH3). Some of the reducing equivalents are transferred in a side-reaction to In addition to NH3, hydrogen is therefore always produced as well. 

The proteinogenic amino acids (see p. 60) can be divided into five families in relation to their biosynthesis. The members of each family are derived from common precursors, which are all produced in the tricarboxylic acid cycle or in catabolic carbohydrate metabolism. An overview of the biosynthetic pathways is shown here further details are given on pp. 412 and 413. 

Plants and microorganisms are able to synthesize all of the amino acids from scratch, but during the course of evolution, mammals have lost the ability to synthesize approximately half of the 20 proteinogenic amino acids. These essential amino acids therefore 

The nutritional value of proteins (see p. 360) is decisively dependent on their essential amino acid content. Vegetable proteins—e.g., those from cereals—are low in lysine and methionine, while animal proteins contain all the amino acids in balanced proportions. As mentioned earlier, however, there are also plants that provide high-value protein. These include the soy bean, one of the plants that is supplied with NH3 by symbiotic N2 fixers (A). 

In mammals, tyrosine (non-essential) is synthesised from phenylalanine (essential) by reaction 

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Many kinds of amino acids (eg, L-lysine, L-omithine, t-phenylalanine, L-threonine, L-tyrosine, L-valine) are accumulated by auxotrophic mutant strains (which are altered to require some growth factors such as vitamins and amino acids) (Table 6, Primary mutation) (22). In these mutants, the formation of regulatory effector(s) on the amino acid biosynthesis is genetically blocked and the concentration of the effector(s) is kept low enough to release the regulation and iaduce the overproduction of the corresponding amino acid and its accumulation outside the cells (22). 

Semifermentation Process. In this process, the metaboHc intermediate in the amino acid biosynthesis or the precursor thereof is added to the medium, which contains carbon and nitrogen sources, and other nutrients required for growth and production, and the metaboHte is converted to the... 

K. M. Herrman and R. L. Somerville, eds.. Amino Acids Biosynthesis and Genetic Regulation, Addison-Wesley Publishing Company, Reading, Mass., 1983. 

In essence, this series of four reactions has yielded a fatty acid (as a CoA ester) that has been shortened by two carbons, and one molecule of acetyl-CoA. The shortened fatty acyl-CoA can now go through another /3-oxidation cycle, as shown in Figure 24.10. Repetition of this cycle with a fatty acid with an even number of carbons eventually yields two molecules of acetyl-CoA in the final step. As noted in the first reaction in Table 24.2, complete /3-oxidation of palmitic acid yields eight molecules of acetyl-CoA as well as seven molecules of FADHg and seven molecules of NADFI. The acetyl-CoA can be further metabolized in the TCA cycle (as we have already seen). Alternatively, acetyl-CoA can also be used as a substrate in amino acid biosynthesis (Chapter 26). As noted in Chapter 23, however, acetyl-CoA cannot be used as a substrate for gluco-neogenesis. 

J. Stetter (ed.), Herbicides Inhibiting Branched Chain Amino Acids Biosynthesis. Recent Development [Chemistry of Plant Protection, Vol. 10], Springer-Verlag, Berlin, 1994. 

Umbarger, H.E. 1978 Amino acid biosynthesis and its regulation. Annual Review of Biochemistry 47 533-606. 

The enzymes glutamate dehydrogenase, glutamine synthetase, and aminotransferases occupy central positions in amino acid biosynthesis. The combined effect of... 

Although uptake and accumulation of most amino acids from the external medium seems to be irreversible, amino acids are excreted into the medium whenever they are overproduced above a given threshold by yeast cells [6], This can occur under a number of specific conditions, namely in mutants with impaired regulation of amino acid biosynthesis, or in the presence of mutations preventing substrate catabolism, or when growth occurs in the presence of metabolic intermediates. It can even occur when growth is arrested under conditions where amino acid synthesis can continue. 

Vaillancourt, F.H., Yeh, E., Vosburg, D.A. et al. (2005) Cryptic chlorination by a non-haem iron enzyme during cyclopropyl amino acid biosynthesis. Nature, 436, 1191-1194. 

Jia MH et al. Global expression proHling of yeast treated with an inhibitor of amino acid biosynthesis, sulfometron methyl. Physiol Genomics 2000 3 83-92. 

K. B. Song, J. W. Seo, and S. K. Rhee, Transcriptional analysis of levU operon encoding saccharolytic enzymes and two apparent genes involved in amino acid biosynthesis in Zymomonas mobilis, Gene, 232 (1999) 107-114. 

Function To donate methyl groups to phospholipid, biogenic amines, thymidine, and amino acid biosynthesis To provide one-carbon fragments at the level of formaldehyde and formic acid for purine and pyrimidine biosynthesis Location Most everywhere... 

Amino Acid Biosynthesis Aromatic amino acid family Aspartate family Glutamate family Pyruvate family Serine family Histidine family Other... 

The primary structure of proteins is not the whole story. To really understand how proteins work, we have got to understand them as three-dimensional objects. So on to higher dimensions in the next chapter. But first, a few paragraphs about another role for the protein amino acids biosynthesis. 

O Leary MJ, DeGaoyer WJ, Doughety TM, Andersov V (1981) Biochem and Biophys Res Comm 100 1320 Herrmann KM, Somerville RL (1983) In Amino Acids Biosynthesis and Genetic Regulation, Addison-Wesley, Reading, Massachusetts, p 1... 

Biochemical Interface Between Aromatic Amino Acid Biosynthesis and Secondary Metabolism... 

It is generally accepted that chloroplasts possess an intact pathway of aromatic amino acid biosynthesis that is tightly regulated. In addition, the subcellular location of some aromatic-pathway isozymes has been shown to be in the cytosol, but whether an intact pathway exists in the cytosol has not yet been proven. The evidence bearing on aromatic amino acid compartmentation and regulation is reviewed, with particular emphasis given to the relationship between primary biosynthesis and secondary metabolism in the cytosol. 

The tightly regulated pathway specifying aromatic amino acid biosynthesis within the plastid compartment implies maintenance of an amino acid pool to mediate regulation. Thus, we have concluded that loss to the cytoplasm of aromatic amino acids synthesized in the chloroplast compartment is unlikely (13). Yet a source of aromatic amino acids is needed in the cytosol to support protein synthesis. Furthermore, since the enzyme systems of the general phenylpropanoid pathway and its specialized branches of secondary metabolism are located in the cytosol (17), aromatic amino acids (especially L-phenylalanine) are also required in the cytosol as initial substrates for secondary metabolism. The simplest possibility would be that a second, complete pathway of aromatic amino acid biosynthesis exists in the cytosol. Ample precedent has been established for duplicate, major biochemical pathways (glycolysis and oxidative pentose phosphate cycle) of higher plants that are separated from one another in the plastid and cytosolic compartments (18). Evidence to support the hypothesis for a cytosolic pathway (1,13) and the various approaches underway to prove or disprove the dual-pathway hypothesis are summarized in this paper. 

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