lecture 6: amino acid metabolism 2 Flashcards
post-absorptive state
insulin decreases, glucagon increases, nitrogen balance net negative
early starvation state
glycogen levels spent, body uses glycerol and AAs to meet energy needs and restore glucose
longer-term starvation
whole body protein degradation rates decrease
increases synthesis of ketone bodies from fatty acids
after long-term starvation
adipose depleted
protein degradation for energy begins again - from muscle tissues
death from starvation is fast approaching
in response to exercise…
work induced hypertrophy develops
increase in synthesis and degradation of protein, but S>D
amino acids absorbed from the GI tract are released….
into portal circulation to liver
system A transport regulation
moves non-polar AAs in Na+ dependent mechanism
activity increased by glucagon and insulin (both use AAs in their processes)
amino acid response elements (AARE)
responsible for transcriptional up/down regulation of genes under amino acid starvation conditions
leucine as a signaling molecule
amino-acid induced insulin secretion
activates GDH in pancreatic B cells, a-ketogluterate in CAC > increased ATP/ADH ratio, closes ATP gated K+ channel, Ca2+ influx > insulin secretion
leads to mTORC1 activation > formation of initiation complex
increases protein synthesis!
transamination
moving a-amino group from one carbon chain to another via transaminase
converts amino acid to keto acid and vice versa
dependent on PLP
only certain AAs can be transaminated, others need to be converted first
deamination. enzyme?
removal of amino group via GDH
nitrogen removed in the form of ammonia
requires NADH or NADPH
where do deamination products go in the body?
liver: ammonia incorporated into urea
kidney: nitrogen excreted as ammonium
GDH substrate
only glutamate (glutamate dehydrogenase)
glucogenic AAs
AAs that produce CAC intermediates that make oxaloacetate
anaplerotic
converted into intermediates of a pathway (in this case, the CAC)
