Protein metabolism Flashcards
What are the functions of dietary protein?
1) replenishes endogenous amino acids 2) Replenishes glycogen stores (via gluconeogenesis) 3) Excess intake is used for ATP production and lipid synthesis 4) Excess nitrogen is excreted
Steps of protein digestion:
1) break the proteins into amino acids 2) split the amino acids into amines and acids (only occurs in the liver) 2.5) Accumulation of excess amines 3) excretion of excess amines.
What cofactor is required for transamination?
PLP; pyridoxal phosphate (carrier of amino groups, performs transaminations, decarboxylations, amino acid racemizations.
What is the role of alpha ketoglutarate in transamination reactions?
a-ketoglutarate is a nitrogen group acceptor (turns into glutamate or glutamine)
What is the role of glutamate dehydrogenase?
transforms glutamate to alpha ketoglutarate without using PLP
What structures serve as temporary storage of NH4+?
Glutamate and glutamine
How is free ammonia neutralized?
Free ammonia is added to glutamate to form glutamine or pyruvate can be converted into alanine. Both glutamine and alanine transport ammonia to the liver.
Which class of enzyme is glutaminase?
Hydrolase
What is the function of glutamate dehydrogenase?
glutamate dehydrogenase is an enzyme in liver mitochondria. Its role it to produce NH4+ for the urea cycle while also generating alpha-ketoglutarate from glutamate.
Pyruvate generating-AAs
CAST - GT ; Cysteine, Alanine, Serine, Threonine, Glycine, Tryptophan.
What is the preferred cofactor for CH3 transfer?
SAM
What cofactor transfers 1-carbon, preferably, Serine
THF (works with oxidation states CH3, CH2OH, CHO) It is a redox co-factor, but not a redox cofactor.
Alpha-ketoglutarate generating AAs
AP HOGG; Arginine, Proline, Histidine, Ornithine, Glutamine, Glutamte.
Oxaloacetate generating AAs
AA - Asparagine, Aspartate
Strategy for forming TCA cycle intermediates from Amino Acids
1) If too big, cleave to make smaller amino acid, 2) If too small, add carbon 3) If otherwise correct, amino transferase, if oxidation state needs changing use a more complex strategy.
