Chapter 9 Protein Regulation Part II Flashcards
What is the function of amino acids besides being the building blocks for peptides and proteins?
Amino acids may be oxidized for fuel.
What is the cofactor we will explore in this chapter?
The pyridoxal phosphate.
From what vitamin is the cofactor pyridoxal pyrophosphate derived?
Vitamin B6. Vitamin B6 is converted to the aldehyde and phosphorylated to form the cofactor pyridoxal pyrophosphate.
How is the cofactor attached to the enzymes that require this cofactor?
Schiff base.
Ammonotelic
excess ammonia directly flushed into the surrounding water.
Ureotelic
organisms that convert ammonia to urea.
Uricotelic
organisms that convert ammonia to uric acid.
Why do we make urea?
ammonia within the body must be eliminated.
What is the source of the nitrogen in urea biosynthesis?
amino acids.
What are the central four amino acids of nitrogen metabolism?
glutamate
glutamine
alanine
aspartate
What molecule forms when amino group is freed from glutamate?
alpha-ketoglutarate
What molecule forms when amino group is freed from glutamine?
alpha-ketoglutarate
What molecule forms when amino group is freed from alanine?
pyruvate
What molecule forms when amino group is freed from aspartate?
oxaloacetate
In what organ does amino acid catabolism take place?
Liver
Chemical Mechanism for amino acid decarboxylation
refer to slides
Chemical Mechanism for amino acid racemization
refer to slides.
What is the role of the pyridoxal phosphate?
temporarily store these electrons through resonance stabilization.
In what form is most of the nitrogen from skeletal muscle transferred to the liver?
alanine
In what form is most of the nitrogen from some muscle and other metabolically active tissues transported to the liver?
glutamine
Write mechanism of transamination
refer to slides.
How are amino groups liberated from glutamate in the liver? What cofactor is required for this process?
through the enzyme L-glutamate dehydrogenase.
cofactor: NAD+ or NADP+
What are allosteric regulators of L-glutamate dehydrogenase?
ADP positive allosteric modulator
GTP negative allosteric modulator
What is the intercellular transport molecule that carries much of the excess ammonia from the tissues to the liver?
glutamine
What is the mechanism for carrying excess ammonia from the muscle to the liver?
Phosphorylation of the side chain carboxyl in glutamate and glutamine creates a good leaving group. Nitrogen of ammonia acts a nucleophile to displace the inorganic phosphate.
Which molecule provides the carbon for urea in the urea cycle?
bicarbonate.
What is the origin of the first and second nitrogen atoms in the urea cycle?
First: ammonia
Second: aspartic acid
What is the origin of the oxygen?
water
How is the balance of nitrogen maintained through both sides of the mitochondrial matrix?
Through the aspartate-glutamate antiporter, for every aspartate that is leaving glutamate carries new nitrogen to regenerate ammonia population.
How is the balance of carbon maintained through both sides of the mitochondrial matrix?
Through the ornithine-citruline antiporter, for every citruline that leaves ornithine enters maintaining the carbon balance.
What is the role of the first two ATP consumed in the urea cycle?
- ATP activates bicarbonate.
- ATP activates carbamide.
What is the role of the third ATP?
Third ATP activates citruline forming citrullyl-AMP intermediate.
Name the major allosteric regulator of the urea cycle.
N-acetyl glutamate.
Explain what enzyme N-acetyl glutamate regulates and how?
N-acetyl glutamate regulates the carbomoyl phosphate synthase-I. N-acetyl glutamate is a positive allosteric regulator of the urea cycle.
Explain what enzyme N-acetyl glutamate regulates and how?
N-acetyl glutamate regulates the carbomoyl phosphate synthase-I. N-acetyl glutamate is a positive allosteric regulator of the urea cycle.
N-acetyl glutamate is produced from acetyl coA and glutamate. Therefore, when these compounds are abundant there is a need for the urea cycle.
What are other ways in which the urea cycle is regulated?
substrate availability and enzyme synthesis turnover.
More protein we eat more urea generated.
How are urea cycle disorders treated?
Limiting protein intake.
