Protein degradation and the urea cycle #18 Flashcards
nitrogen is excreted by the
urea cycle
extracellular and intracellular proteins are degraded by
lysosomal proteases
ubiquitin can be called a
proteasome
amino acids form
heme, nucleotides, cofactors, creatine
what are the major roles of proteolysis
~activation of enzymes, prohormones ~blood clotting/complement cascades ~control of organ growth ~digestion of dietary compounds ~fuel supply ~maintenance of the amino acid pool ~regulation of enzyme activity ~amyloidogenesis ~tissue repair
the most rapidly degrade enzymes all occupy control pints which are
the enzymes rate of degradation is as imp as its rate of synthesis
lysosomes contain
proteases like cathepsins
lysosomes have an internal pH of
5, this contributes to protection of the cell via compartmentation
in well nourished cells lysosomal protein degradation is
non selective
in starving cells lysosomal proteolysis targets
KFERQ motifs in the liver and kidney
regression of the uterus after childbirth is an ex of
lysosome dependent tissue remolding
protein degradation via ubiquitin
~ N end rule: Asp, Arg, Leu, Lys, Phe have half lives of 2-3 min
~ Ala, Gly, Met, Ser, Thr, Val have half lives of >20hrs
~ proteins with Pro, Glu, Ser, Thr are rapidly degraded
~E1 - only one gene in humans, E2 - >20 genes in humans, E3 - HECT(28) domain and RING finger (616)
transamination
interconverts an amino acid and an alpha-keto acid
oxidative deamination of glutamate releases
ammonia
amino acids
are not stored in the cell
