BIOC13H3 Lecture Notes - Aspartate Transaminase, Amino Acid, Citrulline
29 Sep 2013
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Nnnn oooo tttt eeee bbbb oooo oooo kkkk :::: bioc13. Humans can only synthesize about 10 of the 20 amino acids (the simpler non-essential amino acids). In animals, proteases present in stomach and intestines cleave the peptide bond to yield amino acids and small oligopeptides. Carbon skeletons of all twenty amino acids are derived from just 7 metabolic intermediates: 3 glycolytic pathway intermediates: 3-phosphoglycerate, phosphophenolpyruvate, pyruvate. 2 pentose phosphate pathway intermediates: ribose-5-phosphate, erythrose-4-phosphate. Can make any amino acid out of these 7 intermediates. The duodenum secretes a protease called enteropeptidase, which activates several proteolytic enzyme precursors (zymogen) released from the pancreas. One of the pancreatic zymogen is trypsinogen which is cleaved to form the endopeptidase trypsin. Ubiquitin is a 76 amino acid protein found in all eukaryotic cells that is specifically attached to proteins by ubiquitin ligating enzymes. The proteins are cleaved by endo and exo-proteases/peptidases to individual amino acids.
