Sources and Sinks of amino acids
Required only during periods of growth and is generally not required by the adult
Essential amino acids
Pvt. Tim Hall:
Phenylalanine, valine, thryptophan, threonine, isoleucine, methionine, histidine, arginine, leucine, lysine
Waste product of amino acid catabolism
Encephalopathy caused by a loss of funtion of the liver and buildup of ammonia, resulting in ammonia poisoning.
Amino acid metabolism outline
Pathway of dietary amino acid absorption
Amino acid transit via enterocytes
_____ pass through the liver and are used primarily as an alternative energy source by peripheral muscle (especially in fasting) or adipose tissue (in the fed state).
leucine, isoleucine, and valine (the branched nonpolar amino acids) pass through the liver and are used primarily as an alternative energy source by peripheral muscle (especially in fasting) or adipose tissue (in the fed state).
This is because the liver lacks an enzyme required for metabolism of branched chain amino acids.
Pancreatic response to dietary amino acids
The ability of glucagon to stimulate ____ is important to maintain blood glucose levels after ____.
The ability of glucagon to stimulate gluconeogenesis is important to maintain blood glucose levels after a high protein meal.
Regulation of muscle protein breakdown
In skeletal muscle, cortisol exerts its effects at the level of ____.
In skeletal muscle, cortisol exerts its effects at the level of transcription.
Akt/PKB in amino acid metabolism
Regulatory transcription factor that promotes the expression of E3’s that recognize and ubiquitinate skeletal muscle protein, leading to their degradation. (in addition to many other functions)
Muscle is thought to be broken down by ___ in the fasted state.
Muscle is thought to be broken down by the ubiquitin proteasome pathway AND autophagy in the fasted state.
Fate of absorbed amino acids
The glucose-alanine cycle
_____ are often the first step in amino acid metabolism.
Transamination reactions are often the first step in amino acid metabolism.
Reaction catalyzed by aminotransferase
All aminotransfer reactions share a common _____.
All aminotransfer reactions share a common mechanism AND cofactor (B6, pyridoxal phosphate).
High levels of pyruvate in muscle promotes. . .
. . . transfer of amino groups to pyruvate to form alanine.
The common amino group donor is ____.
The common amino group donor is glutamate.
Maple Syrup Urine Disease
The urine in these patients has the odor of maple syrup due to the presence of α-keto acids.
Caused by a partial or complete deficiency in the branched-chain α-keto acid dehydrogenase complex, which causes these amino acids and their ketoacids to accumulate in the blood. Their accumulation interferes with brain function and infants with this disease show symptoms within the first several days after birth. This disease is lethal within the first few weeks of life if left untreated.
Treatment of maple syrup urine disease
The disease is treated using a formula that contains just enough branched chain amino acids for normal growth, but not enough for toxic accumulation of the amino acids or their metabolites.
Branched-chain amino acid metabolism
Aspartate, glutamate, and glutamine metabolism in the liver
Only the ____ from aspartic acid is consumed by the urea cycle
Only the amino group from aspartic acid is consumed by the urea cycle
its carbon skeleton is recycled, via the TCA cycle by forming fumarate
Oxidative deamination of glutamate
Catabolism of amino acid carbon skeletons