Exceptions are aromatic amino acids, histidine, the former biosynthesis and pentose phosphate in the middle Erythrose-4-phosphate, which is synthesized by ATP and phosphoribosyl pyrophosphate. Microbes Plants and plants can synthesize all the amino acids in the body, animals have some amino acids can not be in the body Internal synthesis (essential amino acids). Essential amino acids are typically metabolized by the carbohydrate complex The biosynthesis of nonessential amino acids by multi-step reactions (over 6 steps) About 14 enzymes are required, while the synthesis of essential amino acids requires more, about 60 enzymes versus. Biosynthetic amino acids in addition to the synthesis of protein raw materials, but also for alkaloids, Lignin and other synthetic. On the other hand, amino acids in the body due to amino transfer or oxygen disease Toxins and other keto acid generated to be decomposed, or due to decarboxylation into amines is broken down peptide bond (Peptide bond): The carboxyl group of one amino acid is condensed with the amino group of another amino acid, Remove one molecule of water to form an amide bond. Peptides: Polymers formed by the covalent attachment of two or more amino groups through peptide bonds Things. Amino acids are linked by a peptide bond of the virus, the protein is not compley hydrolyzed products also Is a peptide. Peptides according to their composition, the number of amino acids 2, 3 and 4 are different, respectively, referred to as two Peptides, tripeptides and tetrapeptides, etc., generally contain less than 10 amino acids called oligopeptides (Oligopeptide), composed of more than 10 amino acids polypeptide (polypeptide ), All of which are simply referred to as peptides. The amino acids in the peptide chain are not free amino acid molecules, disease Poison for its amino and carboxyl bond in the formation of peptide bonds have been lost, the virus of this polypeptide and protein Amino acids in the molecule are called amino acid residues. Polypeptides are open chain peptides and cyclic peptides. In the human body is mainly open chain peptide. Open chain peptides have a swim The amino terminus and a free carboxy terminus, respectively, remain free α-amino and α-carboxyl, it is also known as the polypeptide chain N-terminal (amino-terminal) and C-terminal (carboxyl terminal), writing When the N-terminal is generally written on the left of the molecule, and (H) said, and thus started on the polypeptide The amino acid residues in the subfamily are numbered sequentially, while the C-terminus of the peptide is written to the right of the molecule and replaced with ( OH). There are about 200,000 polypeptide and protein amino acid peptide components in the composition And arranged in order to be measured out, many of which are closely related to the medical peptide, respectively Has important physiological functions or pharmacological effects. |