Amino acid synthesis overview

NITROGEN FIXATION AND AGRICULTURE Amino Acid Metabolism Overview Reactions of Amino Groups Synthesis of the Amino Acids... 

In bacteria, each step in fatty-acid sjmthesis is catalyzed by separate enzymes. In vertebrates, however, fatty-acid synthesis is catalyzed by a large, multienzyme complex called a synthase that contains two identical subunits of 2505 amino acids each and catalyzes all steps in the pathway. An overview of fatty-acid biosynthesis is shown in Figure 29.5. 

Production of l.-( Fl Fluoro Amino Acids for Protein Synthesis Overview and Recent Developments in Nucleophilic Syntheses ... 

An overview of protein synthesis is shown in Fig. S.A12. The linear sequence in mRNA that is translated to protein contains four bases, adenine, uracil, guanine and cytosine. The four letters A,U,G and C constitute the mRNA alphabet . This basic alphabet is used in triplets of bases called codons. The codons on mRNA pair up with anticodon or complementary triplets on the tRNA, thus matching the mRNA code to an amino-acid sequence. 

Overview of reactions in protein synthesis. (aab aa2, aa3 = amino acids l, 2, 3.) Protein synthesis requires transfer RNAs for each amino acid, ribosomes, messenger RNA, and a number of dissociable protein factors in addition to ATP, GTP, and divalent cations. First the transfer RNAs become charged with amino acids, then the initiation complex is formed. Peptide synthesis does not start until the second aminoacyl tRNA becomes bound to the ribosome. Elongation reactions involve peptide bond formation, dissociation of the discharged tRNA, and translocation. The elongation process is repeated many times until the termination codon is reached. Termination is marked by the dissociation of the messenger RNA... 

Asymmetric Mannich reactions provide useful routes for the synthesis of optically active p-amino ketones or esters, which are versatile chiral building blocks for the preparation of many nitrogen-containing biologically important compounds [1-6]. While several diastereoselective Mannich reactions with chiral auxiliaries have been reported, very little is known about enantioselective versions. In 1991, Corey et al. reported the first example of the enantioselective synthesis of p-amino acid esters using chiral boron enolates [7]. Yamamoto et al. disclosed enantioselective reactions of imines with ketene silyl acetals using a Bronsted acid-assisted chiral Lewis acid [8]. In all cases, however, stoichiometric amounts of chiral sources were needed. Asymmetric Mannich reactions using small amounts of chiral sources were not reported before 1997. This chapter presents an overview of catalytic asymmetric Mannich reactions. 

Figure 7-6. Overview of the synthesis of nonessential amino adds. Ten amino acids may be produced from glucose via intermediates of glycolysis or the TCA cycle. The eleventh amino acid, tyrosine, is synthesized by hydroxylation of the essential amino acid phenylalanine. TA = transamination GDH- glutamate dehydrogenase.

Protein turnover is not completely efficient in the reutilization of amino acids. Some are lost by oxidative catabolism, while others are used in synthesis of non-protein metabolites. For this reason, a dietary source of protein is needed to maintain adequate synthesis of protein. During periods of growth, pregnancy, lactation, or recovery from illness, supplemental dietary protein is required. These processes are affected by energy supply and hormonal factors. An overview of amino acid metabolism is presented in Figure 17-1. 

A classic example of a typical enzymatic resolution on an industrial scale is the acylase-mediated production of L-methionine. This method has also been applied for the production of L-phenylalanine and L-valine. In addition to acylases, amidases, hydantoinases, and /i-lactam hydrolases represent versatile biocatalysts for the production of optically active L-amino acids. A schematic overview of the different type of enzymatic resolutions for the synthesis of L-amino acids is given in Fig. 2. 

Chapter 19 provides an overview of protein synthesis. The chapter begins with a discussion of the genetic code, the mechanism by which nucleic acid base sequences specify the amino acid sequences of polypeptides. This is followed by discussions of protein synthesis as it occurs in both prokaryotes and eukary-KEY CONCEPTS 1 9.1 otes and a description of the mechanisms that convert polypeptides into their... 

There are two steps in protein synthesis where polarity of information is important. The first is the relationship between the 50 to 30 directionality of mRNA, and the NH3+ to COO- terminal direction of protein synthesis. The utilization of tRNA as the adaptor is the second step where polarity of information is crucial. The tRNA has a bipolar function, it needs to correctly link each amino acid to the corresponding position encoded by the mRNA. Figure 26.1 shows an overview of how mRNA synthesis and protein translation share the same polarity. Moreover, similar to transcription, translation can also be broken down into three discrete components initiation, elongation, and termination. 

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