Endogenous organic synthesis

Endogenous organic synthesis Urey-Miller experiments as a source of prebiotic molecules via the Strecker synthesis for amino acids, HCN polymerisation for purines and pyrimidines and the formose reaction for sugars... 

Peptides - [ANTIBIOTICS - PEPTIDES] (Vol 3) - [TRACE AND RESIDUE ANALYSIS] (Vol 24) -m beer [BEER] (Vol 4) -as endogenous opioids [OPIOIDS, ENDOGENOUS] (Vol 17) -enzymatic synthesis of [ENZYMES IN ORGANIC SYNTHESIS] (Vol 9) -radiolabeling of [RADIOPHARMACEUTICALS] (Vol20)... 

The liver plays a decisive role in the cholesterol metabolism. The liver accounts for 90% of the overall endogenic cholesterol and its esters the liver is also impli-cated in the biliary secretion of cholesterol and in the distribution of cholesterol among other organs, since the liver is responsible for the synthesis of apoproteins for pre-p-lipoproteins, a-lipoproteins, and P-lipoproteins which transport the secreted cholesterol in the blood. In part, cholesterol is decomposed by intestinal micro-flora however, its major part is reduced to coprostanol and cholestanol which, together with a small amount of nonconverted cholesterol, are excreted in the feces. 

Miller S. L. (2000). The Endogenous Synthesis of Organic Compounds in The Molecular Origins of Life, Editor BrackA. CUP (2000). 

All tissues except mature red blood cells are able to manufacture haem for use in the respiratory cytochrome proteins of the electron transport chain. However, the liver is an especially important site of haem synthesis because it (a) is a major organ of erythropoiesis in utero and (b) haem-containing cytochrome-P450 (CYP-450) enzymes play significant roles in hepatic detoxification of drugs, toxins and endogenous waste products (Section 6.4). 

The primary supply of vitamin in humans is not obtained from the diet but rather is derived from the ultraviolet photoconversion of 7-dehydrocholesterol to vitamin Ds in skin. Thus, vitamin Dj synthesis varies with the seasons. D3 is a prohormone and requires further metabolic conversion to exert biological activity in its target organs (Fig. 66.2). The liver and the kidney are the major sites of metabolic activation of this endogenous sterol hormone. The initial transformation of D3 occurs in the liver and is catalyzed by the enzyme 25-OH-D3-hydroxylase... 

Compared with the surprising variety of biochemical compounds that can be readily synthesized in Miller-type one-pot simulation experiments, the suite of organics produced under the conditions proposed by Wachtershauser is quite limited. However, the impressive demonstration that the FeS/H2S combination can reduce nitrogen to ammonia shows that considerable attention should be given to the reducing power of pyrite formation. Primordial life may have not been autotrophic, but should we hesitate to accept the idea that the primitive soup was formed from both extraterrestrial sources and endogenous synthesis in which pyrite production played a role After all, a spicy, thick bouillon is always tastier than a bland, diluted broth. 

Chyba, C. F. and Sagan, C. (1992). Endogenous production, exogenous delivery and impact-shock synthesis of organic molelcules an inventory for the origin of life. Nature, 355, 125-32. 

The endogenous synthesis of organic compounds. In The Molecular Origin of Life, ed. A. Brack. Cambridge University Press. 

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