The Origin of Metabolism

He describes molecular populations mathematically in the way physicists calculate classical dynamic systems. Very exact dynamic equations are devised, while the laws of interaction are left very general. This leads to a general theory of molecular systems, which makes it possible to define what is understood by the origin of metabolism (Dyson, 1999). 

Where did the genes and the genome of this cell come from As cellular metabolism is fully predetermined by gene content, the origin of metabolic (in particular, energy-generating) pathways is actually addressed by this question. 

Weber, A.L. 2002. Chemical constraints governing the origin of metabolism The thermodynamic landscape of carbon group transformations under mild aqueous conditions. Origins Life Evol. Biosph. 32 333-357. 

Cockell CS. The origin and emergence of Ufe under impact bombardment. Philos. Trans. R. Soc. London, Ser. B. 2006 361 1845-1855. Cody GD. Transition metal sulfides and the origin of metabolism. Annu. 

Robert H. White was born in Oakridge, Tennessee, USA, in 1946 and received his BS in Chemistry from Indiana University, Bloomington, in 1968. He obtained his Ph.D. in Biochemistry from the University of Illinois, Urbana-Champaign, in 1974. After one year postdoctoral positions with Professor Stanley L. Miller and then Professor Trevor McMorris at the University of California, San Diego, he moved to Rice University as a lecturer — spectroscopist. In 1980 he joined the Department of Biochemistry at Virginia Tech, Blacksburg. He has been interested in the biosynthesis of coenzymes and how it relates to the origin of metabolism and life. 

Cody GD Transition metal sulfides and the origins of metabolism. Annu Rev Earth Planet Sci 2004, 32 569—599. 

The hyoscine system occurs alone in all young plants and may continue throughout life in specimens in the northern area it may represent the original alkaloid metabolism of the plant. The hyoscyamine system appears only at the age of four to six months, and in the southern area it replaces the hyoscine system almost completely it appears to be an adapted system and may represent the adult alkaloid metabolism of the plant. Usually both systems are present in varying proportions. 

The origin of the success of fl-lactam antibiotics mainly results from the extreme low toxicity of these compounds with regard to human beings. In other words, P-lactam antibiotics have a highly selective toxicity for bacteria since they do not interfere with human metabolism, but inhibit the formation of the cell wall of growing bacteria. 

The experiments with (U-l3C)AIRs showed that this nucleoside supplied all of the carbon atoms of pyramine. Because out of 6 carbon atoms of pyramine, only three may come from the imidazole part of AIRs, it can be concluded that the three other carbon atoms come from the ribose part of this nucleoside. In complete agreement with these results, radioactivity from AIRs, labeled mainly with, 4C in its ribose part, was found to incorporate into the three carbon atoms of pyramine, the origin of which was, at the time, unknown. Owing to the minute amount of AIRs supplied (as compared with that of glucose) in both experiments, the incorporation of label from AIRs after metabolic degradation is ruled out. 

Scheme 3, Hypothetical metabolic transformations of 2-hydroxypropylmethyl nitrosamine with the name of the originator of each hypothesis. Nameless hypotheses are by the authors.

Lack of repeatability of the results of metabolic studies using laboratory strains that have been maintained by repeated transfer for long periods under nonselective conditions may be encountered. These strains may no longer retain their original metabolic capabilities, and this may be particularly prevalent when the strains carry catabolic plasmids that may have been lost under nonselective conditions. For these reasons, strains should be maintained in the presence of a cryoprotectant such as glycerol at low temperatures (-70°C or in liquid Nj) as soon as possible after isolation. Freeze-drying is also widely adopted, and is recommended. 

In today s discussion of the origin of life, the RNA World (Chapter 6) is seen as much more important, and is much better publicized, than the protein world . However, nucleic acids and proteins are of equal importance for the vital metabolic functions in today s life forms. Peptides and proteins are constructed from the same building blocks (monomers), the aminocarboxylic acids (generally known simply as amino acids). The way in which the monomers are linked, the peptide bond, is the same in peptides and proteins. While peptides consist of only a few amino acids (or to be more exact, amino acid residues), proteins can contain many hundreds. The term protein (after the Greek proteuein, to be the first) was coined by Berzelius in 1838. 

Freeman Dyson considers that any theory on the origin of life which begins with cooperative organisation in a large population of molecules, and makes no provision for short circuits in the metabolic pathways, will be met by the criticism just described (Dyson, 1985). 

A question that was posed early on in determining biosynthetic pathways of the pheromones was the origin of the precursors. There was some indication that plant derived compounds could be ingested and modified by the insect into a pheromone. We now know that in some cases this occurs [7], but for the most part pheromones are biosynthesized de novo by the insect [8]. For most of the pheromones studied to date it is apparent that biosynthetic pathways of normal metabolism have been altered to produce specific pheromone components. Several enzymes in these biosynthetic pathways have been modified to produce species specific pheromone components. 

Now, this tentative description of the development of a correlation, later to become information from bases to the synthesis of proteins, by no means solves the problem of the origin of this code nor does it bring into focus the fact that the very proteins which were produced are responsible for the synthesis of the basic metabolic units, formaldehyde and acetic acid and then the amino acids and bases and finally the polymers by catalysts which are the polymers themselves. We do state, however, that the set of reactions quite probably give the most kinetically stable products. Now, the amounts of the different amino acids, lipids, saccharides... 

Unquestionably, the greatest amount of research activity in sterol biosynthesis has been devoted to the elucidation of metabolic origins of unconventional... 

With the isolation of both 9-isocyanopupukeanane (76) and its epimer (77) from P. bourguini, coupled with the results of ichthyotoxicity assays, the suggestion was made that the origin of these compounds may not be exclusively dietary i.e., partial metabolism of 76 to 77 by the nudibranch may be operative [56]. 

There are numerous in vitro and in vivo studies, in which the damaging free radical-mediated effects of iron have been demonstrated. Many such examples are cited in the following chapters. However, recent studies [170,171] showed that not only iron excess but also iron deficiency may induce free radical-mediated damage. It has been shown that iron deficiency causes the uncoupling of mitochondria that can be the origin of an increase in mitochondria superoxide release. Furthermore, a decrease in iron apparently results in the reduction of the activity of iron-containing enzymes. Thus, any disturbance in iron metabolism may lead to the initiation of free radical overproduction. 

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