第十一章 核酸的降解和核苷酸代谢（The eleventh chapter is nucleic acid degradation and nucleotide metabolism）.docVIP

第十一章 核酸的降解和核苷酸代谢（The eleventh chapter is nucleic acid degradation and nucleotide metabolism） Biological functions of nucleic acids DNA and RNA Biological function of nucleotides Synthetic nucleic acid It is an active intermediate of many kinds of biosynthesis Glycogen synthesis, UDP-Glc. Phospholipids were synthesized by CDP- ethanolamine, CDP- two triacylglycerol. Biological energy carriers ATP and GTP Amp is the component of three important coenzyme NAD, FAD, CoA Signal molecules cAMP and cGMP The nucleic acids in food are degraded into various nucleotides by intestinal enzymes, and then are broken down by related enzymes to produce purines, pyrimidines, ribose, deoxy ribose and phosphoric acid, which are then absorbed. The purine and pyrimidine that are absorbed into the body, most of which are broken down, and a small number of which can be re used to synthesize nucleotides. The nucleic acids needed for humans and animals do not depend directly on food. As long as there is enough phosphate, sugar and protein in the food, the nucleic acid can be synthesized normally in the body. Catabolism of nucleic acids: Section 1 catabolism of nucleic acids and nucleotides Enzymatic degradation of nucleic acids Is the 3 nucleotide nucleic acid, 5 - two phosphoric acid ester bond into polymer, the first step is the decomposition of nucleic acid metabolism into nucleotides in two phosphate ester bond enzyme called nuclease (essentially two phosphodiesterase). Depending on the specificity of the substrate, ribonuclease can be divided into RNase, DNase, and nonspecific nuclease. According to the mode of action of enzymes: enzymes, exonuclease. 1 ribonuclease Enzymes that hydrolyze only RNA phosphate two ester bonds (RNase) differ in RNase specificity. Bovine pancreatic ribonuclease (RNaseI), the site of action, is the bond between pyrimidine nucleoside -3 - - phosphate and other nucleotides. RNase T1 (RNaseT1) acts as a bond between 3 - guanine acid and 5 -OH of other nucleotide