Lecture 25: Utilization of Amino Acids Flashcards
Amino Acid Catabolism
-breaks to NH3 and carbon skeleton
Catabolism of amino acid carbon skeleton
-CO2 and water
-glucose
-acetylCoA
-ketone bodies
glucogenic
-can be used for gluconeogenesis
-pyruvate
-TCA intermediates
Ketogenic
-can be used for fatty acid synthesis or ketogenesis
-acetyl-CoA
-acetoacetyl CoA
Glucogenic and ketogenic amino acids
-Ile, Thr, Phe, Tyr, Trp
ketogenic amino acids
-Lys
-Leu
Glucogenic amino acids
-not lys and leu but everything else
Essential amino acids
-cannot be synthesized in sufficient amounts by body
Nonessential amino acids
-can be made by body
-Ala, Asp, Asn, Glu, Ser
Conditionally essential amino acids
-nonessential amino acids that require essential acids for synthesis
-Phe makes Tyr
-Met makes Cys
a-keto acids
-amino acids without amine group
-some available as intermediates in glycolysis ot TCA cycle
a-keto acids:
-alanine
-aspartate
-glutamate
-pyruvate
-oxaloacetate
-a-ketoglutarate
Transamination
-removal of amine group from amino acid
-coupled with production of glutamate from a-ketoglutarate
-catalyzed by aminotransferases
-requires pyridoxal phosphate cofactor
Hotseat
Oxidative deamination by glutamate dehydrogenase
-removes amine group from glutamate by producing ammonia and NADH
-can catalyze reverse reaction with NADPH but ammonia too low under normal conditions for reaction to occur
-glutamate to a-ketoglutarate
ammonia
released amine group of amino acid
Oxidative deamination by amino acid oxidase
-removes amine group as ammonia
-not significant contribution to metabolism
Glutamine
-ammonia transporter
-most abundant amino acid
-transported to intestines and converted to alanine and ammonia
Alanine in the liver
-converted to pyruvate for gluconeogenesis
-converted to ammonia for urea
Glutamine synthetase
-produces glutamine grom glutamate and ammonia
-requires ATP
Flow of nitrogen
-amino acids to glutamate to ammonia
-glutamate to alanine to ammonia
-ammonia to glutamine to alanine
-alanine to ammonia to urea
-liver and skeletal muscles
Glutamate metabolite
GABA
tyrosine metabolite
-dopamine
-norepninephrine
-epinephrine
tryptophane metabolite
-seratonin
-melatonin
histidine metabolite
histamine
glycine metabolite
oxalate
y-aminobutyrate (GABA)
-from glutamate
-inhibitory neurotransmitter
-reduces excitability
-negative change in membrane potential (hyperpolarization)
catecholamine synthesis
-dopamine converted to norepinephrine and epinephrine in adrenal medulla
parkinson’s
not enough dopamine
serotonin
-regulate mood, appetite, sleep, motility in GI tract
Histamine
-allergic response
-vasodilation
-promote wakefullness
-gastric acid release
Oxidation of glycine
-results in oxalate
-may lead to kidney stones
-hyperoxaluria
hyperoxaluria
-excessive oxalate production
-most commons from diet
-lack of enzyme converting glyoxylate to glycine
