L29: Special Products of AA Metabolism Flashcards
Besides glucogenic and ketogenic molecules, what are AAs used to synthesize?
- Creatine phosphate - Hormones, NTs - Pigments - Reducing agents - Heme, pyrimidines, purines
Which three AAs contribute to creatine synthesis? Where does the nitrogen in creatine come from? Where does the synthesis take place? Where does creatine come from in diet?
- glycine, arginine and methionine (s-adenosylmethionine) - nitrogen comes from arginine - liver (some in kidney) - meat and fish
Describe creatine synthesis.
Role of creatine phosphate?
- ATP concentration in resting muscle is high - Creatine kinase is active and phosphorylates creatine, creating creatine phosphate - During exercise, ATP is depleted rapidly and must be regenerated as quickly - Creatine phosphate acts as phosphate group donor in rapid regeneration of ATP for continued muscle contraction, while other energy production is ramping up
Creatine vs Creatinine. To what physical characteristic(s) is creatinine excretion propotional to? Significance of creatinine?
- Around 2% of creatine phosphate spontaneously cyclizes to form creatinine each day - Creatinine excretion is dependent upon skeletal muscle mass, therefore different between tall / short, bodybuilders/lean individuals - Creatinine production and release is fairly constant, therefore with normal kidney function, serum creatinine should remain constant - Sudden changes indicate kidney impairment
Symptoms of imborn errors of creatine metabolism. Treatment?
- Children present with hypotonia, little to no skeletal or cardiac muscle pathology - Neurological symptoms: epileptic seizures, intellectual disability - Treated by creatine administration
What molecules (besides ketogenic/glucogenic) are derived from tyrosine?
- Catecholamines (dopamine, NE, epi) - Thyroid hormones – T3/4 - Melanin
What is dopamine, norepinephrine and epinephrine made from?
- Tyrosine
Outline synthesis of catecholamines. Where does each reaction occur?
What is Parkinson’s disease? Cause, treatment?
- Neurological disease characterized by loss of dopaminergic neurons and formation of Lewy bodies (aggregates of alpha-synuclein protein). Leads to loss of voluntary muscle control, tremor, bradykinesia and postural instability - Symptomatic relief by administration of dopa, but has side effects including nausea, hypotension, cardiac arrhythmias etc.
Outline synthesis of T3/4. What precursor molecule is used?
- Synthesized from tyrosine residue on thyroglobulin, after synthesis of the molecules, proteolysis releases them as free T3/4
What precursor molecule is used to make melanin?
- Tyrosine
Outline synthesis of melanin
- Tyrosinase converts tyrosine to DOPA and then to dopaquinone, which eventuall yields black/brown (eumelanin) or red/yellow (pheomelanin)
In what tissue is melanin synthesized?
- In Golgi of melanocytes - Passes from melanocytes to keratinocytes
Biochemical basis of albinism? Types? Symptoms? Complications?
- Most common form = oculocutaneous albinism type 1, loss of function of tyrosinase - Inability to synthesize melanin in skin, hair and eyes - Complications: impaired vision, early appearance of skin tumors
Synthesis of serotonin
Synthesis of melatonin
