Lecture 6: Protein and Amino Acid Metabolism Flashcards
Amino Acid Pool and where they come from/go
AA Pool - population of free amino acids (100g)
Come From:
- body protein - 400g/day
- dietary protein - 100g/day
- synthed nonessential AA - varies
Go To:
- body protein - 400g/day
- porphyrins, creatine, neurotrans, nucelotides - 30g
- glucose/glycogen, CO2, urea, FA, ketone - varies
Hartnup Disease
- defective transport of nonpolar/neutral AA (Tryptophan) leads to conc. lvls in urine
transporter: kidney/small intestine - mainifests infancy: failure to thrive, nystagmus, tremor, ataxia, photosensitivity
Cystinuria
- defective transport of dimeric cysteine/dibasic AA (Arg, Lys, Ornithine)
- form cysteine crystals in kidneys
- patients present w/renal colic (abdominal pain that comes in waves; linked to kidney stones)
Pyruvate synthesizes what AA?
Alanine
G3P synthesizes what AA?
Serine, Glycine, Cysteine
Oxaloacetate synthesizes what AA?
Aspartate, Asparagine
a-ketoglutarate synthesizes what AA?
glutamate, glutamine, proline, arginine
Proteolytic Enzymes
- degradation of proteins for reabsorption
Exopeptidase: attacks at ends (C-terminus/N-terminus)
Endopeptidase: attacks within protein at specific site (internal peptide bonds)
Intracellular Lysosomal vs Proteosomal Proteolytic Control
Lysosomal: lysosomes have >50 proteolytic enzymes that are active at pH 5, but inactive at pH 7 (cytoplasmic); NONSELECTIVE
- protects functional proteins from degradation in case of lysosomal rupture
Proteolytic: degrades polyubiquinated proteins; SELECTIVE
Extracellular Proteolytic Control
- enzymes secreted as needed
- secreted as inactive zymogens (activated by proteolytic cleavage)
- enterokinase on intestinal epithelial cell (enteropeptidase) activate trypsinogen to trypsin
- trypsin activates more trypsinogen, and converts chymotrypsinogen to chymotrypsin
Ketogenic Amino Acids (2)
Leucine and Lysine
- precursors for keto acids, ketone bodies, and fatty acids
Ketogenic AND Glucogenic Amino Acids (5)
Isoleucine, Tryptophan, Phenylalanine, Tyrosine, Threonine
- can make either ketone bodies OR precursors for glucose synthesis/gluconeogenesis (TCA intermediates0
What amino acids make Succinyl CoA?
Isoleucine, Valine, Methionine, Threonine
What amino acids make a-ketoglutarate?
glutamate
glutamine, histidine, proline ,arginine
What amino acids make fumarate?
phenylalanine, tyrosine