Clinical aspects of protein and amino acid metabolism Flashcards
How is creatinine used clinically?
Estimate of muscle mass
Produced at a constant rate and amount produced depends on muscle mass
Also used as indicator of renal failure (increased in blood)
Name one glucogenic protein
Alanine
Name one ketogenic Amino Acid
Lysine and Leucine
Name one Amino Acid that is both keto and glucogenic
Tyrosine
In what syndrome can you see excessive break down of protein, leading to straie fromation?
Cushings
Name the 9 essential Amino Acids
Isoleucine Lysine Threonine Histidine Leucine Methionine Phenylalanine Tryptophan Valine
What are the two key aminotransferases? WHat are they used for clinically?
Alanine aminotrnsferase and aspartate aminotransferase
Their levels are increased in conditions causing extensive cellular necrosis eg. Viral hepatitis, Autoimmune liver diseases, Toxic injury
Describe refeeding syndrome
When people who have been starved are given a lot of food, the enzymes involved in the urea cycle have been suppressed, so when the Amino Acids have been broken down, they are broken down to ammonia that cannot be removed, ammonia is toxic.
Describe what a defect in the urea cycle would cause
partial loss of enzyme function
Leads to hyperammonia and accumulation and excretion of urea cycle intermediates
What does the severity of a urea cycle defect depend on?
Nature of defect
Amount of protein eaten
Describe 6 symptoms of jurea defect
vomiting lethargy irritability mental retardation seizures coma
How would you manage urea defect?
Low protein diet
replace aas in diet with keto acids
Why is ammonia so toxic?
Readily diffusible and toxic to brain
What can a prblem in amino acid metabolism lead to?
Intellectual impairment
What is the most common Amino Acid metabolism
error? Describe it
Phenylketouria Deficiency in phenylalanie hydroxylase Acculmulation of phenylalanine Get phenylketones in urine Musty smell to urine
Note phenylalanine converted to tyrosine. Tyrosine used to make number of chemicaql (Noradrenaline, adrenaline, dopamine, melanin, thyroid hormone) so these pathways affected
Treatment of phenylketouria?
Low phenylalanin diet
Symptoms of phenylketouria?
Severe intellectual disability developmental delay microcephaly seizures hypopigmentation
Describe homocysteinuria
problem breaking down methionine
Excess homocysteine excreted in urine
Affects connective tissue, muscle, Central Nervous System, and CVS
Treatment of homocysteinurias?
Low methionine diet
Describe how phenylketouria effects brain development
Competes for transport across blood brain barrier via Large neutral Amino Acid transporter
excess phenylalanine can saturate this
other LNAA in brain can decrease–>inhibition of protein and neurotransmitter
causes mental retardation
What syndrome are the symptoms of homocysteinuria like?
Marfans
High levels of homocysteine affects collagen and elastic fibres
lens dislocation and skeletal deeformities caused
