Nitrogen Metabolism, Urea Cycle Flashcards
Glucogenic
catabolism yields pyruvate or intermediates of TCA
Both: tyrosine, isoleucine, phenylalanine, tryptophan
Ketogenic
catabolism yields acetoacetate or precursors
Leucine, lysine
Essential AA
Histidine, methionine, threonine, valine, isoleucine, phenylalanine, tryptophan, leucine, lysine
Alkaptonuria (AR)
Problem: tyrosine degradation
Symptoms: dark urine, arthritis
Carbamoyl phosphate synthetase I deficiency
Problem: urea synthesis
Symptoms: lethargy, convulsions, early death
Homocystinuria (AR)
Problem: methionine degredation
Symptoms: faulty bone development, mental retardation
Maple syrup urine disease (AR)
Problem: isoleucine, leucine, valine degradation (branched amino acids)
Symptoms: vomiting, convulsions, mental retardation, early death
Phenylketonuria (AR)
Problem: conversion of Phenylalanine to tyrosine
Symptoms: neonatal vomiting, mental retardation
AA catabolism
removal of alpha amino group by aminotransferases (B6)
- alpha keto acids used as carbon skeletons
- alpha amino group transferred to alpha KG to make glutamate
Glutamate dehydrogenase removes amino group as ammonia
free ammonia disposed via urea cycle
Glutamate Dehydrogenase
deamination
(+) GDP, ADP
(-) GTP, ATP
Positive Nitrogen balance
more protein turnover and nitrogen intake than losses: growth, pregnancy, recovery
Negative nitrogen balance
inadequate protein intake, disease, blood loss
Glutamine synthetase and glutaminase
transport ammonia to liver
Fate of ammonia
urea, urea cycle (liver)
Mitochondria urea cycle (start)
- CO2 + NH3 + 2ATP = carbamoyl phosphate
- CPS1 - carbamoyl phosphate + ornithine = citruline
- OTC
