Intracellular protein Dietary protein Amino acids NH Carbon skeletons Biosynthesis of amino acids, 4/ nucleotides, and biological amines v Carbamoyl phosphate a-Keto acids Aspartate- arginine- Urea Citric succinate cle acid CO2+H2O shunt of cycle ATE citric acid cle Oxaloacetate U (nitrogen excretion product) Glucose (synthesized in gluconeogenesis)
4. Liver is the maior site of amino acid degradation in vertebrates. a-ketoglutarate(from amino acids ), glutamate (from free ammonia), pyruvate (from muscle amino acids) collects amino groups (in forms of Glu, Gln and Ala to liver mitochondria for further processing The excess NH4+ is excreted directly in bony fishes as urea in most terrestrial vertebrates. or as uric acid in birds and terrestrial reptiles. 3 The carbons in both urea and uric acid are highl oxidized (with most of the energy extracted
4. Liver is the major site of amino acid degradation in vertebrates a-ketoglutarate (from amino acids), glutamate (from free ammonia), pyruvate (from muscle amino acids) collects amino groups (in forms of Glu, Gln and Ala) to liver mitochondria for further processing. • The excess NH4+ is excreted directly in bony fishes, as urea in most terrestrial vertebrates, or as uric acid in birds and terrestrial reptiles. • The carbons in both urea and uric acid are highly oxidized (with most of the energy extracted)
llular protein COo COo Amino acids from ingested→HaN-(-H p R R Amino acids a-Keto acids COO H3N-C-H CH CH. COO COo a-Ketoglutarate Glutamate Coo HN H NH4 cOo COo Glutamine fro Alanine muscle and fr H3N-C-H other tissue CH CH o NH2 Alanine Pyruvate Glutamine NH 4, urea, or uric acid
O H C HIN C NHA H2N--C-NH2 C=0 C Ammonia (as N ammonium ion) O H rea H Uric acid Ammonotelic animals: most aquatic vertebrates Ureotelic animals such as bony fishes and many terrestrial Uricotelic animals: the larvae of amphibia vertebrates; also sharks birds, reptiles
5.PLP facilitates the transamination and other transformations of amino acids Different aminotransferases(e. g. aspartate and alanine aminotransferases), each catalyzes the transfer of the amino group from an amino acid to a-ketoglutarate to form Glu and a a-keto acid Pyridoxal phosphate(PLP), being derived from vitamin B (i. e, pyridoxine) and the prosthetic oups for all the aminotransferases, act as a temporary carrier of the amino groups PLP accepts and then donates an amino group by forming a Schiff base with the amino-donating amino acid and amino-accepting a-keto acid(being a-ketoglutarate in many cases respectively
5. PLP facilitates the transaminatin and other transformations of amino acids • Different aminotransferases (e.g., aspartate and alanine aminotransferases), each catalyzes the transfer of the amino group from an amino acid to a-ketoglutarate to form Glu and a a-keto acid. • Pyridoxal phosphate (PLP), being derived from vitamin B6 (i.e., pyridoxine) and the prosthetic groups for all the aminotransferases, act as a temporary carrier of the amino groups. • PLP accepts and then donates an amino group by forming a Schiff base with the amino-donating amino acid and amino-accepting a-keto acid (being a-ketoglutarate in many cases )respectively