Bessesen Overview of Protein Biochemistry Flashcards
AA subparts
- Amino Group
- Carboxyl group
- R group
How to usefully categorize AA
- Chemically - acidic vs basic
- Where do you get them from? - essential vs nonessential vs. conditionally (yes we could do this ourselves, but capacity is limited, esp during illness)
- Special qualities - sulfur containing, branched chain, or aromatic
- Nutritional - glucogenic (glucose) vs. ketogenic (acetyl-CoA)
Proteolysis
Start with whole protein and need to break down into AA
Occurs in 2 places:
- GI tract - lots of different types of proteases
- In a cell - break down receptors that you don’t need anymore (2 pathways - ubiquitination and lysosomal destruction)
How to get alpha-AA to alpha-keto acid
Transamination - Exchange reaction
AA + alpha-ketoglutarate –> alpha-keto acid + glutamate
Note: you regen the keto acid with a different carbon skeleton
Not energy requiring or producing, entirely concentration driven
What are two aminotransferase reactions that we tend to monitor frequently?
ALT and AST
ALT:
Alanine –> pyruvate
AST:
Aspartate –> oxaloacetate
Glutamate –> alpha-ketoglutarate
- Catalyzed by glutamate dehydrogenase
- Nitrogen is leaving
- Energy is being donated (NAD+ –> NADH)
To go in the other direction you require energy in the form of NADPH
Once the nitrogen comes off of glutamate, where does it go?
It goes into the Urea Cycle
Who is the peripheral carrier for nitrogen from peripheral tissues to the liver?
Glutamine & Alanine:
Glutamate + NH3 –> Glutamine
Glutamine has the extra nitrogen (2 nitrogens), and can go to the liver
Alanine - delivers carbon but also delivers nitrogen via transamination reaction
What takes nitrogen off of glutamine in the liver?
Glutaminase
CO2 + 2ATP + Ammonia leads to what?
Carbamoyl Phosphate - energy requiring
RLS:
Catalyzed by Carbamoyl phosphate synthetase I
