2.1.1 Metabolism II Flashcards
Disorder associated with a defect in glycine and imino amino acid transport?
Joseph’s syndrome or glycinuria
What reactions are mediated by the enzyme serine-threonine dehydratase?
Describe the arginine metabolism pathway from arginine to L-glutamate
Classify the amino acids into three groups: glucogenic (make glucose), ketogenic, and both glucogenic and ketogenic.
Memorize the only ketogenic: Leu, Lys
Cytosolic protein turnover (non-lysosomal) characteristics
- pH near neutrality
- proteases with optimal pH around 7
- Cytosolic proteases are metal requiring
- Proteins are marked with ubiquitin
- Ubiquitin tagged proteins are attacked by proteosome complexes
- Proteosomes with high molecular weight (1500 KDa)
- Ubiquitin covalently modifies lysine residues
- Ubiquitin plays other roles in cellular signaling
Name 4 enzymes that are used in breaking down proteins. (and where they are found)
Carboxyl protease: pepsin (stomach)
Serine proteases: trypsin, chymotrypsin, elastase (pancreatic secretion)
State the important transporters involved in the absorption of amino acids.
Apical: Na + Amino acid symporter
Basal: Na-K ATPase, amino acid channel
Name the 6 characteristics of lysosomal degradation in protein turnover
- lysosomal pH b/t 4 and 5
- variety of proteases with pH optima in this range
- lysosomal porteases act on proteins which are taken up via endocytosis from outside the cell or cell surface (surface receptor)
- The process of endocytosis yields endosomes which fuse with proteosomes which allows for breakdown
- Capable of breaking down proteins all the way to free amino acids
- Use the mannose-6-phosphate marker
What are some of the metabolic intermediates derived from the carbon skeletons of amino acids?
pyruvate, acetoacetyl CoA, acetyl CoA, alpha-ketoglutarate, succinyl CoA, fumarate, oxaloacetate
What are some ways that nitrogen is excreted?
Urea (30g, 86%), ammonium ion, creatine, uric acid
What enzyme is implicated in schizophrenia?
D-amino acid oxidase
Where are polyamines important in the body?
Polyamines are important in the nucleus, as they are used to neutralize the negative charges of nucleic acid
Most amino acids are converted to what two molecules?
Alpha-ketoglutarate and glutamate
The 3 characteristics of AA catbolism (portal/liver)
- After absorption across the gut the AAs are carried to liver via the portal system
- the liver is principal site of both carbon skeleton and nitrogen metabolism and most active organ in synthesis and catabolism
- most nitrogen is removed from the AAs by ezymes which either transaminate or alternatively remove the nitrogen to produce NH3
Describe how glucose can be formed from the citric acid cycle