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Concept
De novo synthesis
Résumé
In chemistry, de novo synthesis () refers to the synthesis of complex molecules from simple molecules such as sugars or amino acids, as opposed to recycling after partial degradation. For example, nucleotides are not needed in the diet as they can be constructed from small precursor molecules such as formate and aspartate. Methionine, on the other hand, is needed in the diet because while it can be degraded to and then regenerated from homocysteine, it cannot be synthesized de novo.
Nucleotide#Synthesis
De novo pathways of nucleotides do not use free bases: adenine (abbreviated as A), guanine (G), cytosine (C), thymine (T), or uracil (U). The purine ring is built up one atom or a few atoms at a time and attached to ribose throughout the process. Pyrimidine ring is synthesized as orotate and attached to ribose phosphate and later converted to common pyrimidine nucleotides.
Cholesterol#Biosynthesis
Cholesterol is an essential structural component of animal cell membranes. Cholesterol also serves as a precursor for the biosynthesis of steroid hormones, bile acid and vitamin D. In mammals cholesterol is either absorbed from dietary sources or is synthesized de novo. Up to 70-80% of de novo cholesterol synthesis occurs in the liver, and about 10% of de novo cholesterol synthesis occurs in the small intestine. Cancer cells require cholesterol for cell membranes, so cancer cells contain many enzymes for de novo cholesterol synthesis from acetyl-CoA.
Fatty acid synthesis
De novo lipogenesis (DNL) is the process by which carbohydrates (primarily, especially after a high-carbohydrate meal) from the circulation are converted into fatty acids, which can be further converted into triglycerides or other lipids. Acetate and some amino acids (notably leucine and isoleucine) can also be carbon sources for DNL.
Normally, de novo lipogenesis occurs primarily in adipose tissue.
Source officielle
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