Untitled Flashcards
How is de novo purine biosynthesis distinguished from de novo pyrimidine biosynthesis?
By inhibition by azaserine (a glutamine analog).
Roles of the reductase and nitrogenase in regard to nitrogen fixation.
Reductase: provides electrons with high reducing power
Nitrogenase: Vanadium cofactor
High reducing power needed to break triple bond.
What are the three ways to make glutamate?
Branch chain amino acid transaminase
Glutamate synthase
Glutamate dehydrogenase (not common)
What is meant when we say that an amino acid is conditionally essential?
They are usually only essential during illness, stress, or other physiological condition that could perturb normal biosynthetic processes.
From an evolutionary perspective, what is the major reason why we do not synthesize our essential amino acids?
Evolution has allowed for enzyme consideration. Since 8-10 enzymes are usually involved in amino acid synthesis, the balance of obtaining essential amino acids from diet conserves energy that would otherwise be used to make them.
Identify the major difference between aminotransferases and amidotransferases in regard to nonessential amino acid synthesis.
Amino: The enzyme that catalyzes the transfer of an amino group to a molecule.
Amido: The enzyme catalyzes transfer of amino group that replaces a carbonyl group on a molecule.
What is the major precursor for proline synthesis in the liver?
Liver can synthesize all nonessential amino acids, but proline must be synthesized a different route via arginine because the lack of a certain enzyme.
Identify the role of the intestine and kidneys in arginine synthesis.
Arginine contains guanadino group, NH4+ needed. If glutamine and glutamate are ultimate precursors for amino acid synthesis, the nitrogen must be obtained via pathways of glutamine and glutamate synthesis.
What role does S-adenosyl methionine play in polyamine synthesis?
S-AM: The sulfur serves as a good facilitator of ammonia transfer while also carrying the methyl group from products.
List three of the amino acid families identifies in class other than the “other amino acids” family.
TCA cycle: Oxaloacetate, a-ketoglutarate
Glycolysis: Pyruvate, PEP, 3-phosphoglycerate
PPP: Ribose-5P
What makes an essential amino acid essential?
Our metabolic ability to produce it’s a-ketoacid.
List three functions of nucleotides aside from genetics.
Glycogen, energy, coenzymes, regulation, group transfers (S-AM)
What two amino acids play a role in making purines and pyrimidines?
Aspartate & glutamine
Describe the mechanism involved in replacing a carbonyl group with an amino group.
Tautomerization then nitrogen attacks intermediate followed by removal of Pi.
Describe 3 methods of regulating purine synthesis in mammals.
Feedback inhibition
PRPP synthesis
Ribose-5P synthesis
IMP–> AMP or GMP
What nucleotide that we discussed could not be made if we were deficient in tetrahydrofolate?
Thymine. THF is the preferred methyl carrier and is made from folic acid. Used in both purine and pyrimidine synthesis.
Describe substrate channeling with regard to PRPP and purine/pyrimidine synthesis.
PRPP synthesis allows for subsequent synthesis of other things such as histidine and pyrimidines and also resulting in a cumulative effect on regulation.
What amino acids can undergo direct deamination and why can these types of amino acids do this?
Serine & threonine because of OH groups
What are the two sources of nitrogen in the urea compound?
Aspartate and ammonium ion from glutamate or glutamine.
What effect does dietary nitrogen have on the enzymes in the urea cycle?
The more dietary nitrogen present, the higher the production of urea.
Diagram (explain) the glucose-alanine cycle.
Muscle: Glucose —–> Pyruvate—>alanine–…
Liver: …—>alanine —-> Pyruvate (also urea out) —> glucose —> (back to muscle)
What role does pyridoxal phosphate play in amino acid metabolism?
Aminotransferases & helping to generate other amino acids.
PLP is a prosthetic group of aminotransferases and is an intermediate carrier of amino groups at the active site of aminotransferases.
