Activation of amino acids, for protein synthesis

Another way in which the phosphorylation state of the adenylate system can regulate the cycle depends upon the need for GDP in step/of the cycle (Fig. 17-4). Within mitochondria, GTP is used largely to reconvert AMP to ADP. Consequently, formation of GDP is promoted by AMP, a compound that arises in mitochondria from the utilization of ATP for activation of fatty acids (Eq. 13-44) and activation of amino acids for protein synthesis (Eq. 17-36). 

The material within the cell membrane is gellike and is termed the cytoplasm or cytosol. It is composed of ions, water, soluble proteins, and enzymes that are involved in generation of energy in the form of ATP by a process termed the tricarboxylic acid cycle (TCA) or Krebs cycle in the absence of oxygen (Figure 1.4). It is also involved in activation of amino acids for protein synthesis (Table 1.5 and Figure 1.4). 

How many high-energy phosphate-bond equivalents are utilized in the process of activation of amino acids for protein synthesis ... 

Mechanism of Activation of Amino Acids for Protein Synthesis. 220... 

Peptidases and proteases play essential 48 roles in protein activation, cell regulation and signaling, in the generation of amino acids for protein synthesis or utilization in other metabolic pathways. 

M. . Krahl Dr. Anfinsen mentioned an attempt to test the possibility that GSH may serve as a source of amino acid for protein synthesis. There may be a n unber of other people who have done negative experiments of this sort. I am one of them. With S Mabeled cysteine and S -labeled GSH, which were kindly supplied by Dr. Tabern and Dr. Hostattler, I measured the amount of S activity incorporated into a crude protein fraction by liver slices in vitro. The molar concentration of cysteine and GSH in the incubation medium was the same in the two respective experiments and the protein fraction was one which had been put through performic-acid treatment. We presume that whatever S was there was not merely attached to the protein via —S—S— linkages. The S was incorporated into this protein fraction 10 times as rapidly from cysteine as it was from GSH. This may mean quite a few things, but gives no support, unfortunately, to the idea that GSH may be an intermediate between cysteine as an amino acid and cysteine in peptide linkage in protein. 

Biological Activity. We have shown that the site of biochemical action for sul fonylureas is the enzyme acetolactate synthase (1,2). This enzyme catalyzes the first common step in the biosynthesis of the essential branched chain amino acids valine and isoleucine. Plants must synthesize these amino acids for protein synthesis and subsequent growth. Therefore, this is a vulnerable or critical... 

Because of its role in activating methionine for transmethylation, this enzyme was initially called the methionine-activating enzyme. With the later discovery of enzymes which activate the carboxyl group of methionine and other amino acids for protein synthesis, this term became somewhat confusing. In this chapter, the trivial name methionine adenosyltransferase or adenosyhransferase, will be used in accord with the recommendation of the Commission on Enzymes (Enzyme Nomenclature, American Elsevier, New York, 1965). The enzyme has also been called S-adenosylmethionine synthetase. 

Rapid degradation of proteins is often induced at certain stages of differentiation. For example, sporeforming bacteria contain a protease that becomes activated upon germination of the spore.131 Within minutes this enzyme digests stored proteins to provide amino acids for the synthesis of new proteins during growth. 

The synthesis of unnatural amino acids and peptides is of great interest since it offers the possibility to design new biologically active protein analogues. One of the possible interesting transformations is side chain oxidation of amino acids, for which MTO can be used. It is reported that various /V-Boc protected amino acids such as methionine (Met), cysteine (Cys), and tryptophan (Trp) can be oxidized with the MT0/H202 system [108]. 

Jhe synthesis of proteins, as characterized by the in vitro incorporation of amino acids into the protein component of cytoplasmic ribonu-cleoprotein, is known to require the nonparticulate portion of the cytoplasm, ATP (adenosine triphosphate) and GTP (guanosine triphosphate) (15, 23). The initial reactions involve the carboxyl activation of amino acids in the presence of amino acid-activating enzymes (aminoacyl sRNA synthetases) and ATP, to form enzyme-bound aminoacyl adenylates and the enzymatic transfer of the aminoacyl moiety from aminoacyl adenylates to soluble ribonucleic acid (sRNA) which results in the formation of specific RNA-amino acid complexes—see, for example, reviews by Hoagland (12) and Berg (1). The subsequent steps in pro-... 

Protein synthesis is essentially a translational process of messenger RNA which has been transcribed from the DNA template. The first reaction is the activation of amino acids by amino-acyl transfer RNA synthetases making use of ATP as an energy source, and the enzymes also attach the amino acid to transfer RNA to form amino-acyl transfer RNA. We have already seen that protein synthesis in plasmodia can be inhibited much further back along the chain, either at the folate co-factor level or during nucleic acid synthesis. It is obvious that interference with RNA transcription from DNA (or with DNA replication), or interference with the availability of essential amino acids, will also affect plasmodial synthesis of protein. Morphological studies of the effects of antimalarials on plasmodia support the occurrence of both modes of action for chloroquine, quinacrine, and quinine. 

Protein Synthesis. Protein biosynthesis is complex, involving more than 300 macromolecules (63). Five stages can be identified involving il) activation of amino acid monomers and transfer to ribosomes, (2) initiation of polymerization, (3) propagation, (4) termination and release, and (5) folding and processing. Ordering of the monomers is dictated by operation of the triplet code in which a sequence of three consecutive nucleotide units on mRNA positions a specific amino acid for polymerization. 

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