Amino Acid Degradation Flashcards
What is the metabolic flow of amino acid nitrogen?
Transamination, deamination, and urea formation
What is transamination?
Transfer of amino group of amino acid to an a-keto acid
Transamination requires which enzymes and which co-factors?
Enzyme: aminotransferases (transaminases: AST & ALT)
Cofactor: pyroxidal phosphate (Vit B6 derivative)
What is oxidative deamination?
Reversible reaction determined by levels of glutamate, a-ketoglutarate, and ammonia (both catabolic and anabolic reactions.
What are the enzymes, co-factors, and allosteric regulators of oxidative deamination?
Enzyme: glutamate dehydrogenase
Cofactor: NAD or NADP
Allosteric regulators: (+) ADP; (-) GTP
What is urea?
It is a low toxicity, water-soluable metabolite, enters the blood, and is excreted in urine.
In which organ does the urea cycle take place?
Liver
What is the cellular location of the reactions in the urea cycle?
First two are in the mitochondrial matrix; the final reactions occur in the cytosol.
What goes into the reaction?
CO2, NH4+, 3 ATP, Aspartate, and H2O
What are the products of the urea cycle?
Urea, 2ADP, 2 Pi, AMP, PPi, fumerate
What is the cellular location of the formation of carbamoyl phosphate from CO2 and ammonia, and what is the energy requirement?
Location: mitochondrial matrix
Energy requirement: 2 ATP
What are the enzymes and allosteric activators in the formation of carbamoyl phosphate from CO2 and ammonia?
Enzyme: carbamoyl phosphate synthetase (CPS-1 - control step)
Allosteric activator: N-acetylglutamate
What two products create citrulline?
Carbamoyl phosphate and ornithine
What are the enzymes and cellular location of the formation of citrulline?
Enzyme: ornithine transcarbamoylase
Cellular location of reaction: mitochondrial matrix
What is a regulation of the urea cycle?
Feeding patterns and need to dispose of nitrogen. Some pattern will still exist during starvation with the breakdown of muscle for fuel.
