Mechanism of Synthesis

There are some very interesting questions of stereospecificity posed by the structure and mode of operation of multienzyme complexes. Reed and Cox 35> have summarized available information on the pyruvate and a-ketoglutarate dehydrogenase complexes, and the fatty add synthetase. The mechanism of synthesis of the peptide antibiotics likewise presents interesting stereochemical problems 36>. 

A third mechanism of synthesis, which was only recently recognized, appears to provide the sole source of asparagine for many bacteria.98b The asparagine-specific transfer RNA tRNAAsn is "mischarged" with aspartic acid to form Asp-tRNAAsn. This compound is then converted to the properly aminoacylated Asn-tRNAAsn by a glutamine-dependent amidotransferase. (The entire ATP-dependent sequence is shown in Eq. 29-6.) The activated asparaginyl group is then transferred from Asn-tRNAAsn into proteins as they are synthesized. 

Write out in detail, using structural formulas, the chemical mechanism of synthesis of an aminoacyl-tRNA and of incorporation of the aminoacyl group into a peptide chain being formed by a ribosome. 

The mechanism of synthesis of polysaccharides is a controversial issue. After discovery, by Cardini s group, that starch may be polymerized on a protein,152,153 it was suggested153 that all nascent, polysaccharide chains might be covalently associated with a protein. Connected with the formation of glycoprotein is the involvement of lipid intermediates. We shall analyze the biosynthetic pathways of polysaccharides where partial or complete evidence of this kind of mechanism has been educed. 

It should be emphasized that, although lipid-activated sugars provide the only well known mechanism for transglycosylation reactions occurring across a membrane, other mechanisms cannot be precluded. More, active research is needed in order to elucidate the mechanism of synthesis of several plant glycans. 

The mechanism of synthesis of the amino and hydroxy acids was investigated.15 It was shown that the amino acids were not formed directly in the electric discharge but were the result of solution reactions of smaller... 

There are three types of glycoproteins based on their structure and the mechanism of synthesis N-linked glycoproteins, O-linked glycoproteins, and nonenzymatic glycosylated glycoproteins. 

Fig. 1. Diagrammatic representation of mechanism of synthesis and processing of protein hormones.

On the basis of the evidence available to date, several hypotheses on the mechanism of synthesis of carbamyl-P may be maintained how-... 

This article surveys methods and mechanisms of synthesis and characterization of hydroxy telechelic polymers by the free radical process. Some practical applications have been considered. 

Miller SL. The mechanism of synthesis of amino acids by electric discharges. Biochim. Biophys. Acta. 1957 23 480-489. 

Oro J (1961) Mechanisms of synthesis of adenine from hydrogen cyanide under possible. Primitive earth conditions. Nature 191 1193-1194... 

Figure 17.11. Mechanism of Synthesis of Citryl CoA hy Citrate Synthase. The condensation of oxaloacetate and acetyl CoA proceeds through an enol intermediate. The subsequent hydrolysis of citryl CoA yields citrate and CoA.

Figure 27.36. Telomere Formation. Mechanism of synthesis of the G-rich strand of telomeric DNA. The RNA template of telomerase is shown in blue and the nucleotides added to the G-rich strand of the primer are shown in red. [After E. H. Blackburn. Nature 350(1991) 569.]...

The principle that tissue constituents are in a state of continuous synthesis and degradation is well established. The rate of turnover of the various constituents of connective tissues varies and, whereas the turnover of collagen is very slow, that of the ground substance is relatively rapid. Although the detailed mechanism of synthesis of the acid mucopolysaccharides is as yet unknown, in a number of instances the general pattern of synthesis has emerged. 

The mechanism of synthesis of hyaluronic acid in mammalian tissues appears to resemble that present in bacteria. The synthesis of hyaluronic acid in tissue culture has been widely studied (GIO, H7), and labeled hyaluronic acid is synthesized in vitro from uniformly labeled D-glucose by explants of human synovial tissue (Yl). An enzyme system has recently been found in mesodermal tissues which catalyzes the synthesis of hyaluronic acid directly from UDP-GNAc and UDP-GA (A5). 

The kinetics and mechanism of synthesis and decomposition of macrocyclic compounds are regarded as one of the most important aspects in the chemistry of these compounds. The majority of papers concern metal ions complexing with preliminarily synthesized macrocyclic ligands and metal ion substitutions by other metal ions in the preliminarily prepared complexes. Template synthesis, the most promising approach to the directed preparation of macrocyclic compounds with desired structures [17], plays a still more decisive role in the chemistry of macrobicyclic complexes with encapsulated metal ion. However, the literature contains only scarce data on the kinetics and the mechanism of the template synthesis of macrocyclic compounds because of the difficulties encountered in experimental determinations of kinetic and thermodynamic parameters, such as low product yields, nonaqueous media, high temperatures, and side reactions. 

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