Exam 3 Protein Metabolism Flashcards
Daily protein intake
15-22% of total energy
0.8-1 g/kg
Protein storage pool
Not actual storage pool like lipids
Used for structural/signaling fxn
Post-translationally modified amino acids
Hydroxy-proline and hydroxy-lysine (collagen, Vit C)
Gamma carboxyglutamate (prothrombin, Vit K)
Ornithine (urea cycle)
Two pathways of protein degradation
Ubquination
Lysosomal
Transamination - overview
Removal of the N group to use in gluconeogenesis
Bidirectional
Mainly liver (some kidney, intestine, muscle)
Need Vit B6 (PLP)
Transamination - enzyme and mech
Aminotransferase
N transferred to a-ketoglutarate
Released as NH3 - regenerating a-ketoglutarate
Sulfur containing amino acids
Cysteine
Methionine
Ketogenic amino acids (essential)
Leucine
Lysine
Both keto/glucogenic (essential)
Tyrosine
Phenyl-alanine
Tryptophan
Isoleucine
Vitamins C, K, B6 important rxns
C= Prolyl hydroxylase and lysyl hydroxylase activity (collagen, schiff base formation) K= Gamma glutamyl carboxylase (prothrombin) B6= Transamination, PLP holds N (schiff base formation)
Control points for protein catabolism
- Directionality of transamination
- N-Acetylglutamate activation of CPS-1
- Directionality of GluDH
- Energy feedback on GluDH
Glucogenic amino acids (essential)
Metionine
Valine
Histadine
Threonine
Carbamoyl phosphate synthetase I
Mitochondria
Urea cycle
Ammonia is source of nitrogen
Activator: N-acetyl glutamate
Carbamoyl phosphate synthetase II
Cytosol Pyrimidine synthesis Glutamine is source of nitrogen Activator: ATP Inhibitor: UTP
Prolyl hydroxylase vs. lysyl hydroxylase
PH: Pro -> Hyp (important for H bonds?)
LH: Lys -> Hyl (important for covalent bond via lysyl oxidase)
Both hydroxylases require Vit C
Tissues and ammonia toxicity/transport
Peripheral tissues: glutamine for transport to liver
Muscle: alanine for transport to liver
Liver: produce urea to Kidney
Kidney: removes urea (liver )and ammonia (glutamine)
Glutamine crosses BBB
Glutamate Dehydrogenase
Exists in all tissues
Concentration dependent
Activated by ADP, inhibited by ATP
Thyroid hormone synthesis
Thyroglobulin (140 Tyr, few w/ I)
T4 = 4 I
T3 = 3 I (deiodinase)
TSH functions
release T3/T4 (bound and transported by TBG)
increase absorption of I
Homocysteinuria causes
Defect in methionine synthase
Defect in cystathionine ß synthase
Defect in MTHFR gene (produces THF)
Hyperhomocysteinemia consequences
CV disease
Impaired wound healing
Cervical CA
Homocysteinuria signs and symptoms
Mental retardation
Osteoporosis
CVD
Marfanoid presentation
Cysteinuria causes
Defective PCT transporter of COLA Cysteine Ornithine Lysine Arginine Cysteine insoluble in large amounts (Tx. acetazolamide)
Purine synthesis basics
Start with sugar -> activate
Add base
Add phosphates
